We provide alternating current practice exercises, instructions, and a learning material that allows learners to study outside of the classroom. We focus on alternating current skills mastery so, below you will get all questions that are also asking in the competition exam beside that classroom.
List of alternating current Questions
| Question No | Questions | Class |
|---|---|---|
| 1 | In a step-down transformer the secondary coil has number of turns A. strength B. less c. alternating D. primary |
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| 2 | In series ( L R ) circuit ( X_{L}=R ) and power factor of the circuit is ( P_{1} ) When capacitor with capacitance ( C ) such that ( X_{L}=X_{C} ) is put in series, the power factor becomes ( P_{2} ) Calculate ( P_{1} / P_{2} ) |
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| 3 | If ( L, C ) and ( R ) represent inductance, capacitance and resistance respectively, than which of the following does not represent dimensions of frequency? ( ^{A} cdot frac{1}{R C} ) в. ( frac{R}{L} ) c. ( frac{1}{sqrt{L C}} ) D. ( frac{c}{L} ) |
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| 4 | A ( 120 mathrm{V}, 60 mathrm{W} ) lamp is to be operated on 220 ( mathrm{V}, 50 mathrm{Hz} ) supply mains Calculate what value of pure inductance which would be required so that the lamp runs on correct value of power A ( cdot 1.174 ) B. 2.348 c. 3.522 D. 4.696 |
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| 5 | An alternating voltage ( boldsymbol{E}= ) ( mathbf{5 0} sqrt{mathbf{2}} sin (mathbf{1 0 0} t) boldsymbol{V} ) is connected to a 1 ( mu F ) capacitor through an ac ammeter. What will be the reading of the ammeter? A . ( 10 mathrm{mA} ) B. ( 5 m A ) c. ( 5 sqrt{2} ) mA D. ( 10 sqrt{2} mathrm{mA} ) |
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| 6 | Assertion: A resistance is connected to an ac source. Now a capacitor is included in the series circuit. The average power absorbed by the resistance will remain same. Reason: By including a capacitor or an inductor in the circuit average power across resistor does not change. A. A and R both are true and R is correct explanation of B. A and R both are true but R is not the correct explanation of c. A is true R is false D. A is false and R is true |
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| 7 | A resistance and inductance are connected in series with a source of alternating e.m.f. Derive an expression for resultant voltage impedance and phase difference between current and voltage in alternating circuit. |
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| 8 | A capacitor has a resistance of ( 1200 M Omega ) and capacitance of ( 22 mu F ) When connected to an AC supply of frequency ( 80 mathrm{Hz} ), the alternating voltage supply required to drive a current of 10 virtual amperes is A. ( 904 sqrt{2} V ) B. 904 D. ( 452 mathrm{v} ) |
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| 9 | A pure inductor of self inductance ( 1 mathrm{H} ) is connected across an alternating voltage of ( 115 mathrm{V} ) and frequency ( 60 mathrm{Hz} ). The reactance ( X_{L} ) and peak current respectively are в. 337.12, 0.43 А c. 377.1Omega, 0.43 A D. 3.7Omega, 0.42 A |
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| 10 | A light bulb is rated at ( 100 W ) for a ( 220 V ) supply. Find the peak voltage of the source: A. ( 111 V ) в. ( 211 V ) ( mathbf{c} cdot 311 V ) D. ( 411 V ) |
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| 11 | 14. The peak value of an alternating emf E given by E = E. cost is 10 V and frequency is 50 Hz. At time t=(1/600) s, the instantaneous value of emf is (a) 10 V (b) 5/3 v (c) 5V (d) 1V |
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| 12 | If the inductance of a coil in 1 henry then its effective resistance in a ( D . C ) circuit will be ( A cdot infty ) B. zero ( c cdot 1 Omega ) D. 2 ( Omega ) |
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| 13 | TC 17. In an ac circuit, the instantaneous emf and current are given by € = 100 sin 30 t i = 20 sin ( 307- In one cycle of alternate current, the average power consumed by the circuit and the wattles current are, respectively (a) 50,0 (b) 50, 10 50 (d) 7,0 1000 v2.10 (JEE Main 2018) |
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| 14 | Assertion The quantity ( L / R ) possesses dimension of time Reason To reduce the rate of increase of current through a solenoid, we should increase the time constant ( (boldsymbol{L} / boldsymbol{R}) ) A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 15 | A charged ( 30 mu mathrm{F} ) capacitor is connected to a ( 27 mathrm{mH} ) inductor. The angular frequency of free oscillations of the circuit is A ( cdot 1.1 times 10^{3} r a d s^{-1} ) B. ( 2.1 times 10^{3} r a d s^{-1} ) c. ( 3.1 times 10^{3} r a d s^{-1} ) D. ( 4.1 times 10^{3} r a d s^{-1} ) |
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| 16 | A resistance ( boldsymbol{R} ) and a capacitor ( boldsymbol{C} ) are joined to a source of ( boldsymbol{A} boldsymbol{C} ) of constant e.m.f and variable frequency. The potential difference across ( C ) is ( V ) If the frequency of ( boldsymbol{A} boldsymbol{C} ) is gradually increased, ( boldsymbol{V} ) will A. increase B. decrease c. remain constant D. first increase and then decreas |
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| 17 | A step-up transformer operates on a ( 230 mathrm{V} ) line and supplies aload of 2 amp. The ratio of the primary and secondary windings is ( 1: 25 . ) The current in the primary is ( A cdot 15 A ) B. 12.5 A ( c cdot 25 A ) D. 50 A |
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| 18 | ( mathbf{A} ) ( mathbf{5 0 0} Omega ) resistor and a capacitor ( C ) are connected in series across ( 50 H z . A C ) supply mains. The r.m.s potential difference recorded on voltmeter ( V_{1} ) and ( V_{2} ) are ( V_{1}=120 V ) and ( V_{2}=160 mathrm{V} . ) The power taken from the mains is: 4. ( 480 mathrm{W} ) В. 240 И c. ( 28.8 W ) D. ( 14.4 mathrm{W} ) |
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| 19 | Distinguish between step-up and step down transformer. |
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| 20 | The unit of susceptance is ( A cdot ) ohm B. ohm ( ^{-1} ) c. ohm/cm D. ohm/m |
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| 21 | The average power dissipation in pure inductance in AC circuit, is A ( cdot 1 / 2 L i^{2} ) B . ( 2 L i^{2} ) c. ( L i^{2} / 4 ) D. zero |
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| 22 | What is the main differences between a step-up transformer and a step-down transformer? |
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| 23 | Assertion: A capacitor blocks direct current in the steady state.
Reason : The capacitive reactance of the capacitor is inversely proportional to frequency f of the source of emf |
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| 24 | A sinusoidal voltage ( V=200 sin 314 t ) is applied to a ( 10 Omega ) resistor. Find power dissipated as heat. ( mathbf{A} .500 W ) в. ( 1000 mathrm{W} ) c. ( 2000 W ) D. 3000W |
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| 25 | A transmitter transmits at a wavelength of ( 300 mathrm{m} . ) A condenser of capacitance ( 2.4 mu F ) is being used. The value of the inductance for the resonant circuit is approximately B. ( 10^{-6} ) Н ( z ) ( c cdot 10^{-8} mathrm{Hz} ) D. ( 10^{-10} ) Н ( z ) |
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| 26 | ( ln ) an oscillating ( L-C ) circuit in which ( C=4.00 mu F, ) the maximum potential across the capacitor during the oscillations is ( 1.50 V ) and the maximum current through the inductor is ( 50.0 m A ) What is the frequency of the oscillations? |
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| 27 | The frequancy of oscillation of current in the inductor is- A ( cdot frac{1}{3 sqrt{L C}} ) B. ( frac{1}{6 pi sqrt{L C}} ) c. ( frac{1}{sqrt{L C}} ) D. ( frac{1}{2 pi sqrt{L C}} ) |
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| 28 | A resonant A.C. circuit contains a capacitor of capacitance ( 10^{-6} mathrm{F} ) and an inductor of ( 10^{-4} ) H. The frequency of oscillations will be : ( mathbf{A} cdot 10^{5} ) Нz в. 10 Н ( z ) ( ^{mathrm{c}} cdot frac{10^{5}}{2 pi} mathrm{Hz} ) D. ( frac{10}{2 pi} ) нг |
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| 29 | Compute the energy stored in the capacitor at ( t=2.00 m s ) A. ( 9.5531 mu J ) B. ( 6.5531 mu J ) c. ( 3.5531 mu J ) D. ( 2.5531 mu J ) |
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| 30 | At low frequency a condenser offers: A. high impedance B. low impedance C. zero impedance D. impedance of condenser is independent of frequency |
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| 31 | A circuit consists of a resistor,an inductor and a capacitor connected in series. If the resistance of a resistor is ( 25 Omega ) and the value of inductive reactance is equal to capacitive reactance, then the net impedance of the circuit will be : A . ( 5 Omega ) B. 25Omega c. ( 125 Omega ) D. ( 625 Omega ) |
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| 32 | If an alternating current ( boldsymbol{i}=boldsymbol{i}_{m} sin omega boldsymbol{t} ) is flowing through a capacitor then voltage drop ( Delta V_{C} ) across capacitor ( C ) will be? A ( cdot-frac{i_{m}}{omega C} sin omega t ) в. ( -frac{i_{m}}{omega C} cos omega t ) c. ( -frac{i_{m}}{omega C}left(sin omega t+frac{pi}{4}right) ) D. ( frac{i_{m}}{omega C}left(sin omega t-frac{pi}{4}right) ) |
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| 33 | ( ln ) a series ( L-C-R ) circuit, current in the circuit is ( 11 A ) when the applied voltage is ( 220 V . ) Voltage across the capacitor is ( 200 V . ) If value of resistor ( 20 Omega, ) then the voltage across the unknown inductor is A. zero в. ( 200 mathrm{V} ) ( c .20 V ) D. None of these |
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| 34 | In a transformer the transformation ratio is ( 0.3 . ) If ( 220 mathrm{V} ) ac is fed to the primary, then the voltage across the secondary will be A . ( 44 mathrm{V} ) B. 55 ( c cdot 60 v ) D. 66 V |
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| 35 | ( ln ) an ( A C ) circuit ( V ) and ( I ) are given by ( boldsymbol{V}=mathbf{1 0 0} sin (mathbf{1 0 0} boldsymbol{t}) ) volt, ( boldsymbol{I}= ) ( 100 sin left(100 t+frac{pi}{3}right) ) amp the power dissipated in the circuit is A . ( 5.0 k W ) в. ( 2.5 k W ) c. ( 1.25 k W ) D. zero |
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| 36 | The rms value of current in an ( A C ) circuit is ( 10 A . ) What is the peak current? A . ( 14.1 A ) B. ( 35.2 A ) ( mathrm{c} .58 .9 A ) D. ( 23.5 A ) |
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| 37 | How many primary volts must be applied to a transformer with a secondary to primary turns ratio of 0.1 to obtain a secondary voltage of ( 9 V ? ) A . ( 9 V ) B. ( 90 V ) ( mathbf{c} .900 V ) D. ( 0.9 V ) |
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| 38 | A broadcasting centre broadcasts at 300 metre band. A capacitor of capacitance ( 2.5 mu mathrm{F} ) is available. The value of the inductance required for resonant circuit is nearly A ( cdot 1 times 10^{-4} mathrm{H} ) В. ( 1 times 10^{-8} mathrm{H} ) c. ( 1 times 10^{-6} H ) D. ( 1 times 10^{-2} H ) |
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| 39 | A step up transformer converts ( 100 mathrm{V} ) at primary to ( 300 mathrm{V} ) at secondary. If the primary current is ( 6 A ), then the secondary current is ( A ) A . 4 B. 8 c. 2 D. 10 |
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| 40 | (c) 200 S2 and 1.UH T 27. In the circuit shown in the figure, R is a pure resistor an inductor of negligible resistance (as compared to R) is a 100 V, 50 Hz ac source of negligible resistance. With either key K, alone or K, alone closed, the current is I. If the source is changed to 100 V, 100 Hz the current with K alone closed and with K, alone closed will be, respec tively, KIA K2 As (b) 10, 21, (C) 21., 70 (d) 210,0 WW |
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| 41 | () 0.UA 30. In a series LCR circuit, the voltage across the resistance, capacitance and inductance is 10 V each. If the capacitance is short circuited, the voltage across the inductance will be (a) 10 V (b) 10/2 V (c) (10/3)V (d) 20 V |
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| 42 | The values of ( X_{L}, X_{C} ) and ( R ) in series with an A.C. circuit are ( 8 Omega, 6 Omega ) and ( 10 Omega ) respectively. The total impedance of the circuit will be ( Omega ) A . 10.2 B. 12.2 c. 10 D. 24.4 |
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| 43 | 50. The power factor of the circuit in the figure is 1/2 The capacitance of the circuit is equal to 2 sin(1001) 10 S2 w 0.1 H mm (a) 400 uF (c) 500 uF (b) 300 uF (d) 200 uF |
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| 44 | ( ln L C R operatorname{series} A C ) circuit A. If ( R ) is increased current will decrease B. If ( L ) is increased current will decrease c. If ( C ) is increased current will increase. D. If ( C ) is increased current will decrease. |
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| 45 | The peak voltage of an AC supply is ( 300 V . ) What is the rms voltage? A ( .121 .2 V ) ( V ) B. 212.1V c. ( 343.4 V ) D. ( 434.3 V ) |
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| 46 | Current of ( frac{50}{pi} H z ) frequency is passing through an A.C circuit having series combination of resistance ( boldsymbol{R}=mathbf{1 0 0} mathbf{Omega} ) and inductor ( L=1 H, ) then phase difference between voltage and current is A ( cdot 60^{circ} ) B. ( 30^{circ} ) ( c cdot 45^{circ} ) D. ( 90^{circ} ) |
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| 47 | 8. In an LCR circuit capacitance is changed from C to For the resonant frequency to remain unchanged. th inductance should be change from L to (a) 4L (b) 2L (c) L/2 (d) L/4 (AIEEE 2004 |
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| 48 | ( ln L_{-} C ) oscillation, maximum charge on capacitor is ( Q_{0} . ) The current in the circuit, when ( 50 % ) energy is electrical and ( 50 % ) is magnetic is A ( cdot frac{Q_{0}}{sqrt{L C}} ) B. ( frac{Q_{0}^{2}}{sqrt{L C}} ) с. ( frac{Q_{0}}{2 sqrt{L C}} ) D. ( frac{Q_{0}}{sqrt{2 L C}} ) |
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| 49 | At inductance ( 1 H ) is connected in series with an ( A C ) source of ( 220 mathrm{V} ) and ( mathbf{5 0} boldsymbol{H} z . ) The inductive resistance (in ohm) is : A ( .2 pi ) в. ( 50 pi ) ( c .100 pi ) D. ( 1000 pi ) |
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| 50 | A resistor of resistance ( 100 Omega ) is connected to an AC source ( epsilon= ) ( (12 V) sin left(250 pi s^{-1}right) t ) Find the power consumed by the bulb. |
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| 51 | Express ( q ) as a function of time. A ( cdot 10^{4} cos left(6.28 times 10^{3} tright) ) B ( cdot 10^{-4} cos left(9.28 times 10^{3} tright) ) ( mathbf{c} cdot 10^{-4} cos left(6.28 times 10^{3} tright) ) D ( cdot 10^{-4} cos left(6.28 times 10^{-3} tright) ) |
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| 52 | An inductor ( 2 / pi mathrm{F} ) and a resistor ( 100 / pi ) are connected in series across a source of emf ( mathbf{v}=mathbf{1 0} sin 100[pi mathrm{t}] . ) Here ( mathrm{t} ) is in second. (a) find the impedance of the circuit find the energy dissipated in the circuit in 20 minutes. |
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| 53 | In an L.C.R series a.c circuit, the current, the current A. is always in phase with the voltage B. always lags the generator voltage C . always leads the generator voltage D. None of these |
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| 54 | The instantaneous value of emf and current in an A.C. circuit are; ( boldsymbol{E}= ) ( 1.414 sin left(100 pi t-frac{pi}{4}right), I= ) ( 0.707 sin (100 pi t) . ) The admittance of the circuit will be mho. A ( cdot frac{1}{sqrt{2}} ) B. ( sqrt{2} ) ( c cdot frac{1}{2} ) D. |
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| 55 | In the secondary coil of a step up transformer, the number of turns of the copper wire are : A. More and the wire is thick B. More and the wire is thin c. Less and the wire is thick D. Less and the wire is thin |
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| 56 | When an a.c. source of e.m.f. ( boldsymbol{E}= ) ( E_{0} sin 100 t ) is connected across a circuit, it is observed that voltage leads the current by a phase angle ( frac{pi}{4} . ) If the circuit consists possible only R-L, R-C or L-C in series the two elements could be. B. ( R=10 Omega, C=1000 mu F ) c. ( R=100 Omega, C=1000 mu F ) D. ( R=10 Omega, L=100 m H ) |
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| 57 | Statement A: With an increase in the frequency of AC supply inductive reactance increases. Statement B: With an increase in the frequency of AC supply capacitive reactance increase. A. A is true but B is false B. Both A and B are true c. A is false but B is true D. Both A and B are false |
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| 58 | A resistance ( (boldsymbol{R})=12 Omega ; ) inductance ( (L)=2 ) henry and capacitive reactance ( C=5 m F ) are connected in series to an ac generator, then: A. at resonance, the circuit impedance is zero B. at resonance, the circuit impedance is ( 12 Omega ) c. the resonance frequency of the circuit is ( 1 / 2 pi ) D. at resonance, the inductive reactance is less than the capacitive reactance |
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| 59 | A device that increases the voltage of an alternating current is called a(n) A. Electric motor B. Galvanometer c. step-up transformer D. step-down transformer |
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| 60 | A choke is preferred to a resistance for limiting current in AC circuit because: A. Choke is cheap B. There is no wastage of power c. choke is compact in size D. Choke is a good absorber of heat |
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| 61 | Keeping the source frequency equal to the resonating frequency of the series LCR circuit, if the three elements, ( L, C ) and ( R ) are arranged in parallel, show that the total current in the parallel LCR circuit is minimum at this frequency. Obtain the current RMS value in each branch of the circuit for the elements and source specified as below for this frequency. The figure shows a series LCR circuit connected to a variable frequency ( 230 V ) source. ( boldsymbol{L}=mathbf{5 . 0 H}, boldsymbol{C}=mathbf{8 0} boldsymbol{mu} boldsymbol{F}, boldsymbol{R}= ) ( 40 Omega ) |
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| 62 | An LC circuit contains a ( 20 mathrm{mH} ) inductor and a ( 25 mu ) F capacitor with an initial charge of 5 mC. The total energy stored in the circuit initially is A . 5 J в. 0.5 c. 50 D. 500 J |
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| 63 | The current flowing through the resistor in a series LCR a.c. circuit, is ( boldsymbol{I}=varepsilon / boldsymbol{R} ) Now the inductor and capacitor are connected in parallel and joined in series with the resistor as shown in figure. The current in the circuit is now. (Symbols have their usual meaning) A . equal to I B. more than I c. less than 1 D. zero |
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| 64 | A sinusoidal voltage ( V=200 sin 314 t ) is applied to a ( 10 Omega ) resistor. Find rms voltage. A . ( 141.4 V ) B. ( 314.2 V ) c. ( 519.6 V ) D. 278.9V |
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| 65 | When the current in the inductor has half its maximum value, what is the charge on the capacitor? A ( cdot 1.33 times 10^{6} C ) B. ( 9.33 times 10^{-6} C ) ( mathbf{c} cdot 4.33 times 10^{-6} C ) D. ( 7.33 times 10^{6} C ) |
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| 66 | 1. When 100 volts dc is supplied across a solenoid, a current of 1.0 ampere flows in it. When 100 volt ac is applied across the same coil, the current drops to 0.5 ampere. If the frequency of ac source is 50 Hz, then the impedance and inductance of the solenoid are (a) 200 2 and 0.55 henry (b) 100 2 and 0.86 henry (c) 200 S2 and 1.0 henry (d) 100 2 and 0.93 henry |
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| 67 | What is the inductance of the inductor? A ( .9 .31 mu H ) в. о.931цн.931ин D. ( 93.1 mu H ) |
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| 68 | The number of turns in the primary coil of a transformer is 200 and the number turns in the secondary coil is 10 If 240 volt a.c is applied to the primary the output from seconsry will be: A . 48 v B. 24 c. ( 12 mathrm{v} ) ( D cdot 6 v ) |
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| 69 | An ac voltage is applied to a resistance ( mathrm{R} ) and an inductor ( mathrm{L} ) in series. If ( mathrm{R} ) and the inductive reactance are both equal to ( 3 Omega, ) the phase difference between the applied voltage and the current in the circuit is: A. zero в. ( c cdot frac{pi}{4} ) D. ( frac{pi}{2} ) |
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| 70 | A ( 300 Omega ) resistor is connected in series with a ( 0.800 H ) inductor. The voltage across the resistor as a function of time is ( V_{R}=(2.50 V) cos [(950 r a d / s) t] ) Determine the inductive reactance of the inductor. |
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| 71 | In an a.c. circuit ( mathrm{V} ) and I are given by ( V=50 sin 50 t ) volt and ( I= ) ( 100 sin (50 t+pi / 3) mathrm{mA} . ) The power dissipated in the circuit A. 2.5 kw B. 1.25 kw c. ( 5.0 mathrm{kw} ) D. 500 watt |
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| 72 | In the circuit shown below, the key Kis closed at ( t=0 . ) The current through the battery is: A. ( frac{mathrm{VR}_{1} mathrm{R}_{2}}{sqrt{mathrm{R}_{1}^{2}+mathrm{R}_{2}^{2}}} ) at ( mathrm{t}=0 ) and ( frac{mathrm{V}}{mathrm{R}_{2}} ) at ( mathrm{t}=infty ) ( frac{V}{R_{2}} a t t=0 ) and ( frac{Vleft(R_{1}+R_{2}right)}{R_{1} R_{2}} ) at ( t=alpha ) C ( cdot frac{mathrm{V}}{mathrm{R}_{2}} mathrm{att}=0 ) and ( frac{mathrm{VR}_{1} mathrm{R}_{2}}{sqrt{mathrm{R}_{1}^{2}+mathrm{R}_{2}^{2}}} ) at ( mathrm{t}=infty ) ( frac{Vleft(R_{1}+R_{2}right)}{R_{1} R_{2}} a t t=0 ) and ( frac{V}{R_{2}} ) at ( t=infty ) |
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| 73 | In an a.c. circuit the voltage applied is ( boldsymbol{E}=boldsymbol{E}_{0} sin omega boldsymbol{t} . ) The resulting current in the circuit is ( boldsymbol{I}=boldsymbol{I}_{0} sin left(boldsymbol{omega} boldsymbol{t}-frac{boldsymbol{pi}}{2}right) . ) The power consumption in the circuit is given by – A ( cdot quad P=frac{E_{0} I_{0}}{sqrt{2}} ) B . ( P= ) zero c. ( _{P}=frac{E_{0} I_{0}}{2} ) D. ( P=sqrt{2} E_{0} I_{0} ) |
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| 74 | An LCR series circuit is under resonance. If ( I_{m} ), is current amplitude, ( V_{m} ) is voltage amplitude, ( R ) is the resistance, ( Z ) is the impedance, ( X_{L} ) is the inductive reactance and ( X_{C} ) is the capacitive reactance, then ( ^{mathrm{A}} cdot_{I_{m}}=frac{Z}{V_{m}} ) в. ( _{I_{m}}=frac{V_{m}}{X_{L}} ) ( mathbf{c} cdot_{I_{m}}=frac{V_{m}}{X_{C}} ) D. ( _{I_{m}}=frac{V_{m}}{R} ) |
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| 75 | 43. Power factor is one for (a) pure resistor (b) pure inductor (c) pure capacitor (d) either an inductor or a capacitor |
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| 76 | The primary and secondary coil of a transformer have 50 and 1500 turns respectively. If the magnetic flux ( phi ) linked with primary coil is given by ( phi=phi_{0}+4 t, ) where is in webers, ( t ) is time in seconds and ( phi ) is a constant, the output voltage across the secondary coil is: ( A cdot 150 V ) B. 90 c. ( 120 v ) D. ( 180 mathrm{V} ) |
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| 77 | In the circuit of given figure (1) and (2) are ammeters. Just after key ( boldsymbol{K} ) is pressed to complete the circuit, the reading is A. maximum in both 1 and 2 B. zero in both 1 and 2 c. zero in 1 , minimum in 2 D. maximum in 1, zero in 2 |
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| 78 | A series ( L C R ) circuit containing a resistance of ( 120 Omega ) has angular resonance frequency ( 4 times 10^{5} ) rad ( s^{-1} ) At resonance the voltages across resistance and inductance are ( 60 V ) and ( 40 mathrm{V} ), respectively. The value of inductance ( L ) is A. ( 0.1 mathrm{mH} ) в. ( 0.2 mathrm{mH} ) c. ( 0.35 mathrm{mH} ) D. ( 0.4 mathrm{mH} ) |
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| 79 | What is the average power dissipation in an ideal capacitor in AC circuit? ( mathbf{A} cdot 2 C V^{2} ) в. ( frac{1}{2} C V^{2} ) c. ( Z ) ero D. ( C V^{2} ) |
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| 80 | A LC-circuit contains a ( 20 m H ) inductor and a ( 50 mu F ) capacitor with an initial charge of ( 10 m C . ) The resistance of the circuit is negligible. Let the instant the circuit is closed be ( t=0 ) (a) What is the total energy stored initially. Is it conserved during the LCoscillations? (b) What is the natural frequency of the circuit? (c) At what times is the energy stored? (i) completely electrical (ie., stored in the capacitor)? (ii) completely magnetic (i.e., stored in the inductor)? (d) At what time is the total energy shared equally between the inductor and the capacitor |
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| 81 | ( ln ) an ( A C ) circuit, the potential across an inductance and resistance joined in series are respectively ( 16 V ) and ( 20 V ) The total potential difference across the circuit is ( mathbf{A} cdot 20.0 V ) B . ( 25.6 V ) c. ( 31.9 V ) D. 33.6 ( V ) |
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| 82 | the values of ( I, C ) and ( R ) for a circuit are 1 ( mathrm{H}, 9 mathrm{F}, ) and ( 3 Omega ). what is the quality factor for the circuit at resonance? ( A ) B. 9 ( c cdot 19 ) D. 13 |
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| 83 | The ratio of primary voltage to secondary voltage in a transformer is ‘n’. The ratio of the primary current to secondary current in the transformer is ( A ) B. ( 1 / n ) c. ( n^{2} ) D. ( 1 / n^{2} ) |
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| 84 | The inductor in a ( L-C ) oscillation has a maximum potential difference of ( 16 V ) across the inductor of ( 3 m H ) and maximum energy of ( 160 mu J . ) The value of capacitor in ( L-C ) circuit is : ( mathbf{A} cdot 0.8 mu F ) B. ( 0.625 mu F ) c. ( 1.6 mu F ) D. ( 1.25 mu F ) |
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| 85 | 12. In an AC generator, a coil with N turns, all of the same area A and total resistance R, rotates with frequency o in a magnetic field B. The maximum value of the emf generated in the coil is. (a) N.A.B.R. (b) N.A.B. O (c) N.A.B.R. O (d) N.A.B (AIEEE 2006) |
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| 86 | ( ln ) an ( A . C . ) circuit a capacitor of ( 1 mu F ) value is connected to a source of frequency 1000 rad/sec. The value of capacitive reactance will be A . ( 10 Omega ) в. 100Omega c. ( 1000 Omega ) D. ( 10,000 Omega ) |
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| 87 | n the circuit shown in figure, the ( A C ) source gives a voltage ( V= ) ( 20 cos (2000 t) . ) Neglecting source resistance, the voltmeter and ammeter readings will be A. ( 0 V .2 .0 ) В. ( 0 V, 1.4 A ) ( c .5 .6 V, 1.4 ) ) ( .8 V, 2.0 A ) |
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| 88 | The diagram below in Fig. shows the core of a transformer and its input and output connections. The name of the transformer is (step-up, stepdown) transformer. |
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| 89 | 12. An ac voltage is represented by E = 220 V2 cos(501) How many times will the current become zero in 1 s? (a) 50 times (b) 100 times (C) 30 times (d) 25 times |
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| 90 | A circuit containing a ( 20 Omega ) resistor and 0.1 ( mu F ) capacitor in series is connected to 230 V AC supply of angular frequency 100 rad ( s^{-1} . ) The impedance of the circuit is A ( cdot 10^{5} Omega ) B . ( 10^{4} Omega ) ( mathbf{c} cdot 10^{6} Omega ) D. ( 10^{10} Omega ) |
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| 91 | If the bandwidth of a filter increases: A. Q factor decreases B. the roll-off rate increases c. the half-power frequency decreases D. the center frequency decreases |
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| 92 | An inductive coil has a resistance of 100 ( Omega ). When an a.c. signal of frequency ( 1000 H z ) is fed to the coil, the applied voltage leads the current by ( 45^{circ} . ) What is the inductance of the coil? ( mathbf{A} cdot 10 m H ) в. ( 12 m H ) c. ( 16 m H ) D. ( 20 m H ) |
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| 93 | In the method using the transformers, assume that the ratio of the number of turns in the primary to that in the secondary in the step-up transformer is ( 1: 10 . ) If the power to the consumers has to be supplied at ( 200 mathrm{V} ), the ratio of the number of turns in the primary to that in the secondary in the step-down transformer is ( A cdot 200: 1 ) B. 150:1 c. 100: 1 D. 50: |
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| 94 | The alternating emf applied and the current flowing in an ( A C ) circuit are represented by ( boldsymbol{E}=boldsymbol{E}_{0} sin omega boldsymbol{t} ) and ( I_{0} sin left(omega t+frac{pi}{2}right) ) respectively. The power loss in the circuit will be A . zero в. ( frac{E_{0} I_{0}}{2} ) c. ( frac{E_{0} I_{0}}{sqrt{2}} ) D. ( frac{E_{0} I_{0}}{4} ) |
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| 95 | toppr ( = ) Q Type your question. ( B ) ( c ) ( D ) |
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| 96 | The maximum charge on the capacitor is given as ( (text { in } n C) ) | 12 |
| 97 | 13. In the circuit shown below, the ac source has voltage V= 20cos(ot) volts with o= 2000 rad/sec. The amplitude of the current will be nearest to 692 50 F 5 mH, 422 mm (b) 3.3 A (a) 2 A (c) 2115 A (d) V5 A |
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| 98 | In a series L-C circuit, if ( L=10^{-3} mathrm{H} ) and ( C=3 times 10^{-7} F ) is connected to a ( 100 V-50 H z ) a.c. source, the impedance of the circuit is A ( cdot frac{10^{5}}{3 pi}-10 pi ) В. ( 0.1 pi-3 times 10^{-5} pi ) ( ^{mathbf{C}} cdot frac{10^{5}}{3 pi}-frac{pi}{10} ) D. None of these |
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| 99 | If the values of ( L, C ) and ( R ) in a series ( boldsymbol{L}-boldsymbol{C}-boldsymbol{R} ) circuit are ( 10 mathrm{mH}, 100 mu boldsymbol{F} ) and ( 100 Omega ) respectively then the value of resonant frequency will be ( ^{mathbf{A}} cdot frac{10^{3}}{2 pi} H z ) в. ( 2 times 10^{3} H z ) c. ( _{2 times frac{10^{3}}{p i}} H z ) D. ( 10^{3} H z ) |
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| 100 | The value of alternating emf in the following circuit will be A. 220 volt B. 140 volt c. 20 volt D. 100 volt |
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| 101 | A transformer has 500 turns of the primary winding and 10 turns of the secondary winding. Determine the secondary voltage if the secondary circuit is open and the primary voltage is ( 120 mathrm{V} ) |
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| 102 | Define quality factor. | 12 |
| 103 | The primary of a transformer has 40 turns and works on 100 volt and 100 watt. Then the number of turns in the secondary to step up voltage to ( 400 mathrm{V} ) and the current in the secondary and primary will be A. ( 260,0.25 mathrm{A}, 2 mathrm{A} ) B. 160, 0.25A, 1A c. ( 360,0.55 mathrm{A}, ) 1А D. None of these |
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| 104 | The current in LCR circuit is maximum when : A ( . X_{L}=0 ) В . ( X_{L}=X_{C} ) c. ( X_{C}=0 ) D. ( X_{L}^{2}+X_{C}^{2}=1 ) |
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| 105 | A circuit consists of a coil with inductance ( L ) and an uncharged capacitor of capacitance C.The coil is in a constant uniform magnetic field such that the flux through the coil is ( mathbf{Phi} . mathbf{A t} ) time ( t=0, ) the magnetic field is abruptly switched off. Let ( omega_{0}=1 / sqrt{L C} ) and ignore the resistance of the circuit. Then: A . current in the circuit is ( I(t)=(Phi / L) cos omega_{0} t ) B. Magnitude of the charge on the capacitor is ( |Q(t)|= ) ( 2 C omega_{0} mid sin omega_{0} t ) C. initial current in the circuit is infinite D. initial charge on the capacitor is ( C omega_{0} Phi ) |
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| 106 | What do we name the device which increases the emf? A. electric generator B. step-up transformer c. electric motor D. none of these |
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| 107 | Joule’s Law for heat produced is valid for A . Resistance B. Inductance c. capacitance D. Battery |
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| 108 | 51. In an LR circuit connected to a battery, the rate at whin energy is stored in the inductor is plotted against time during the growth of current in the circuit. Which of the following best represents the resulting curve? Rate Rate (a) (b) Time → Time Rate Rate (d) Time – Time min lenodot |
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| 109 | A transformer converts ( 200 V ) a.c. to ( mathbf{5 0} boldsymbol{V} ) a.c.The secondary has ( mathbf{5 0} ) turns and load across it draws ( 300 m A ) current.Calculate the current in the primary: |
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| 110 | A certain step-up transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is A . 0.2 B. 0.4 ( c .5 ) D. 25 |
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| 111 | The inductance of a resistanceless coil is 0.5 henry. In the coil, the value of alternating current is ( 0.2 mathrm{A} ) whose frequency is 50 Hz. The reactance of circuit is ( A cdot 15.7 Omega ) в. ( 157 Omega ) c. ( 1.57 Omega ) D. 757Omega |
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| 112 | A pure capacitor is connected in an ( A C ) circuit.The power factor of the circuit will be ( A ) B. infinity c. zero D. 0.5 |
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| 113 | If a transformer have turn ratio 5 frequency ( 50 H z ) root mean square value of potential difference on primary 100 volts and the resistance of the secondary winding is ( 500 Omega ) then the peak value of voltage in secondary winding will be (the efficiency of the transformer is hundred percent) A. ( 500 sqrt{2} ) 2 в. ( 10 sqrt{2} ) c. ( 50 sqrt{2} ) 2 D. ( 20 sqrt{2} ) |
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| 114 | ‘Z’ is not. A. Atomic number B. Impedance C. Zeta potential D. Partition function |
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| 115 | Four different circuit components are given in each situation of List 1 and al the components are connected across an ac source of same angular frequency ( omega=200 mathrm{rad} s^{-1} . ) The information of phase difference between the current source voltage in each situation of List 1 is given in List ( 2 . ) Match the circuit components in List 1 with the corresponding List 2 |
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| 116 | ( frac{k}{k} ) | 12 |
| 117 | In the figure shown, ( q ) is in coulomb and ( t ) in second. At time ( t=1 s ) This question has multiple correct options A ( cdot V_{a}-V_{b}=4 V ) в. ( V_{b}-V_{c}-1 V ) C ( . V_{c}-V_{d}=16 V ) D. ( V_{a}-V_{d}=20 V ) |
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| 118 | If the reading in voltmeter ( V_{1} ) is ( 40 V ) then what is the reading of voltmeter ( V_{2} ) |
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| 119 | What is the value of inductance ( L ) for which the current flowing is maximum in a series LCR circuit with ( C=10 mu F ) and ( omega=1000 s^{-1} ? ) A. ( 100 m H ) в. ( 1 m H ) c. Cannot be calculated unless ( R ) is known D. ( 10 m H ) |
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| 120 | The transformer voltage induced in the secondary coil of a transformer is mainly due to: A. a varying electric field B. a varying magnetic field c. the vibrations of the primary coil D. the iron core of the transformer |
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| 121 | The given graph(a) and (b) represent the variation of the opposition offered by the circuit element to the flow of alternating current, with frequency of the applied emf. Identify the circuit element corresponding to each graph. |
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| 122 | n the circuit shown in figure, the ( A C ) source gives a voltage ( V= ) ( 20 cos (2000 t) . ) Neglecting source resistance, the voltmeter and ammeter readings will be A. ( 0 V .2 .0 ) В. ( 0 V, 1.4 A ) ( c .5 .6 V, 1.4 ) ) ( .8 V, 2.0 A ) |
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| 123 | A capacitor acts as an infinite resistance for A . ( D C ) B. ( A C ) c. ( D C ) as well as ( A C ) D. neither ( A C ) nor ( D C ) |
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| 124 | An ( L-C-R ) series circuit with ( L= ) ( mathbf{0 . 1 2 0 H}, boldsymbol{R}=mathbf{2 4 0 Omega}, ) and ( boldsymbol{C}=mathbf{7 . 3 0 mu} boldsymbol{F} ) carries an rms current of ( 0.450 A ) with a frequency of ( 400 H z . ) What is the impedance of the circuit? |
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| 125 | For a transformer, the turns ratio is 3 and its efficiency is ( 0.75 . ) The current flowing in the primary coil is ( 2 A ) and the voltage applied to it is ( 100 mathrm{V} ). Then the voltage and the current flowing in the secondary coil are respectively. A. ( 150 V, 1.5 A ) B . ( 300 V, 0.5 A ) c. ( 300 V, 1.5 A ) D. ( 150 V, 0.5 A ) |
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| 126 | An ideal inductor is in turn put across ( 220 V, 50 H z ) and ( 220 V, 100 H z ) supplies. The current flowing through it in the two cases will be then A. equal B. different c. zero D. infinite |
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| 127 | The number of turns in the primary and the secondary coils of a transformer are 1000 and 3000 respectively. If the primary of the coil is connected to 80 volt ac, then what is the potential difference per turn of the secondary coil ( ? ) A . 240 B. 24 c. ( 0.24 v ) D. 0.08 ( v ) |
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| 128 | can be moved from ( a ) to ( b, ) connecting either inductance ( L ) or capacitance ( C ) to a resistor ( R ) when the key is pressed the switch ( S ) will be at either ( a ) or ( b ). In column ( I, ) the variation of physical quantities charge,current,voltage etc.in time are given in terms of constants ( C^{prime} s ) and ( K^{prime} s ) the values of which depends on emf ( V, R, L ) and ( C . ln ) column ( boldsymbol{I} boldsymbol{I}, ) the physical quantities under different switch positions are given. the variation in column ( boldsymbol{I} ) may correspond to one or more quantities of Column ( boldsymbol{I} boldsymbol{I} ) |
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| 129 | Average power consumed by the circuit | 12 |
| 130 | A transformer having the efficiency of ( 90 % ) is working on ( 200 V ) and ( 3 k W ) power supply. If the current in the secondary coil is ( 6 A ), the voltage across the secondary coil and the current in the primary coil respectively are: A. ( 300 V, 15 A ) в. ( 450 V, 15 A ) c. ( 450 V, 13.5 A ) D. ( 600 V, 15 A ) |
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| 131 | Define quality factor of resonance in series LCR circuit. What is its Sl unit? |
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| 132 | A transformer steps up an ac supply from 220 to 2200 V. If the secondary coi of the transformer has 2000 turns, Then find the number of turns in its primary coil. |
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| 133 | An ( A C ) voltage source of variable angular frequency ( omega ) and fixed amplitude ( V_{0} ) is connected in series with a capacitance ( C ) and an electric bulb of resistance ( boldsymbol{R} ) (inductance zero) When ( omega ) is increased A. the bulb glows dimmer B. the bulb glows brighter C. total impedance of the circuit is unchanged D. total impedance of the circuit increases |
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| 134 | When a voltage ( V_{s}=200 sqrt{2} sin (omega t+ ) ( left.15^{circ}right) V ) is applied to an ac circuit, the current in the circuit is found to be ( i= ) ( 2 sin [omega t+(pi / 4)] A . ) If the average power consumed in the circuit is ( x sqrt{6} W ). Find ( boldsymbol{x} ) |
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| 135 | Prove for an a.c. circuit: ( boldsymbol{P}_{boldsymbol{a v}}=boldsymbol{V}_{boldsymbol{r m s}} times boldsymbol{I}_{boldsymbol{r m s}} times cos boldsymbol{phi} ) |
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| 136 | The power loss in an ( A C ) circuit is ( E_{r m s} ) ( I_{r m s}, ) when in the circuit there is only A. ( C ) в. ( L ) ( c . R ) D. ( L, C ) and ( R ) |
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| 137 | An ( L C R ) series circuit with ( R=100 Omega ) is connected to a ( 200 mathrm{V}, 50 mathrm{Hz} ) a.c source. When only the capacitance is removed, the current leads the voltage by ( 60^{circ} . ) When only the inductance is removed, the current leads the voltage by ( 60^{circ} . ) The current in the circuit is : A ( .2 A ) в. ( 1 A ) c. ( frac{sqrt{3}}{2} A ) D. ( frac{2}{sqrt{3}} A ) |
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| 138 | In a series resonant circuit, the AC voltage across resistance ( R, ) inductor and capacitor ( C ) are ( 5 vee, 10 vee ) and ( 10 ~ V ) respectively. The AC voltage applied to the circuit will be A . ( 10 v ) B. 25 ( c cdot 5 v ) D. 20 |
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| 139 | Which of the following statements is true? Heat produced in a current carrying conductor depends upon: |
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| 140 | Voltage induced in the secondary coil of a transformer is mainly due to : A. The iron core of the transformer B. The vibrations of the primary coil c. A varying induced electric field D. A varying induced magnetic field |
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| 141 | State whether given statement is True or False
The quality factor (Q) is the ratio of true |
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| 142 | The average power dissipated in a pure inductor is A ( cdot frac{1}{2} V I ) B. ( V I^{2} ) c. ( frac{V I^{2}}{4} ) D. zero |
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| 143 | If the value of ( C ) in a series RLC circuit is decreased, the resonant frequency A. is not affected B. increases c. is reduced to zero D. decreases |
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| 144 | A coil has resistance 30 ohm and inductive reactance 20 Ohm at ( 50 mathrm{Hz} ) frequency. If an ac source, of 200 volt, ( 100 mathrm{Hz}, ) is connected across the coil, the current in the coil will be : ( mathbf{A} cdot 4 cdot 0 mathrm{A} ) B. ( 8.0 mathrm{A} ) c. ( frac{20}{sqrt{13}} ) A D. 2.0 A |
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| 145 | Find the dimensions of ( frac{1}{sqrt{L C}}(L= ) Inductance, ( C=text { Capacitance }) ) ( mathbf{A} cdot T^{-1} ) B. ( T^{-2} ) ( c . T ) D. ( L ) |
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| 146 | In a step-up transformer, the number of turns in the primary are than the number turns in the secondary. A. more B. less c. same as D. None of the above |
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| 147 | If the resistance in parallel with a parallel resonant circuit is reduced, the bandwidth A. disappears B. becomes sharper c. increases D. decreases |
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| 148 | A ( 20 Omega ) resistor, ( 1.5 mathrm{H} ) inductor and ( 35 mu F ) capacitors are connected in series with ( 200 V, 50 H z ) ac supply. Calculate the impedance of the circuit and also find the current through the circuit? |
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| 149 | A transformer converts ( 200 mathrm{V} ) ac into ( 2000 mathrm{V} ) ac. Calculate the number of turns in the secondary if the primary has 10 turns. |
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| 150 | A series RLC circuit is made as shown in the figure with an ( A C ) source of ( 60 vee ) 20 Hz. Then This question has multiple correct options A. the rms current through the resistor R is 4.2 A B. the effective potential difference between P and should be ( 42 mathrm{v} ) c. the instantaneous current leads the source voltage by 45 D. the instantaneous current lags behind the applied voltage by ( 45^{circ} ) |
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| 151 | The current in resistance ( boldsymbol{R} ) at resonance is ( A cdot ) zero B. minimum but finite c. maximum but finite D. infinite |
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| 152 | A condenser of capacity ( C ) is charged to a potential difference of ( V_{1} . ) The plates of the condenser are then connected to an ideal inductor of inductance L. The current through the inductor when the potential difference across the condenser reduces to ( V_{2} ) is: A ( cdot frac{Cleft(V_{1}^{2}-V_{2}^{2}right)}{L} ) B. ( frac{Cleft(V_{1}^{2}+V_{2}^{2}right)}{L} ) c. ( sqrt{frac{Cleft(V_{1}^{2}-V_{2}^{2}right)}{L}} ) D. ( sqrt{frac{Cleft(V_{1}-V_{2}right)^{2}}{L}} ) |
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| 153 | What is the reactance in ohms of a ( 2.00 H ) inductor at a frequency of ( mathbf{5 0 . 0 H z} ? ) |
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| 154 | In a series combination of ( mathrm{R}, mathrm{L} ) and ( mathrm{C} ) to an AC source at resonance, if ( mathrm{R}=20 Omega ), then impedance ( Z ) of the combination is A . ( 20 Omega ) B. zero ( Omega ) ( c cdot 1 Omega ) D. 400 ( Omega ) |
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| 155 | A capacitor has capacitance ( 0.5 n F . A ) choke of ( 5 mu H ) is connected in series. An electromagnetic wave of wavelength ( lambda ) is found to resonate with it. Find ( lambda ) (in meter) ( mathbf{A} cdot 10 pi ) в. ( 20 pi ) c. ( 30 pi ) D. ( 5 pi ) |
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| 156 | Above the resonant frequency, A. the frequency of the body is less than the frequency of the external periodic force. B. the frequency of the body is greater than the frequency of the external periodic force. C. the frequency of the body is exactly equal to the frequency of the external periodic force. D. both (A) and (B) |
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| 157 | ( ln ) an ( A C ) circuit, voltage ( V=V_{0} sin omega t ) and inductor L is connected across the circuit.Then the instantaneous power will be ( ^{mathrm{A}} cdot frac{V_{0}^{2}}{2 omega L} sin omega t ) B. ( frac{-V_{-}^{2}}{2 omega L} ) sinwt c. ( frac{-V_{0}^{2}}{2 omega L} sin 2 omega t ) D. ( frac{V_{0}^{2}}{omega L} sin 2 omega t ) |
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| 158 | The unit of ( sqrt{boldsymbol{L} boldsymbol{C}} ) is A. Henry B. Farad c. second D. Ampere |
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| 159 | A protons is about 1840 times heavier than an electron. When it is accelerated by a potential difference of ( 1 k V ), its kinetic will be:- A. ( 1840 mathrm{keV} ) B . ( 1 / 1840 mathrm{keV} ) c. ( 1 mathrm{keV} ) D. ( 920 mathrm{keV} ) |
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| 160 | 64. In the following electrical network at t < 0 (figure), key is placed on (1) till the capacitor got fully charged. Key is placed on (2) at t=0. Time when the energy in both the capacitor and the inductor will be same for the first time is (1) (2) (a) VLC (b) 37 LC (c) VLC (1) 27 JIC |
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| 161 | puudu ideal choke takes a current of 10 A when connected to an ac supply of 125 V and 50 Hz. A pure resistorm the same conditions takes a current of 12.5 A. If the are connected to an ac supply of 100 V and 40 Hz then the current in series combination of above resistor and inductor is (a) 10/2 A b) 12.5 A (c) 20 A (d) 10 A |
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| 162 | (C) SU umes (u) 25 Wes 13. The rms value of an ac of 50 Hz is 10 A. The time taken by an alternating current in reaching from zero to maximum value and the peak value will be (a) 2 x 10-2s and 14.14 A (b) 1 x 10-2 s and 7.07 A (c) 5 x 10-3s and 7.07 A (d) 5 x 10’s and 14.14 A |
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| 163 | In the circuit shown, the switch ( S_{1} ) is closed for long time and at ( t=0 ) s, the switch ( S_{2} ) is closed and ( S_{1} ) is opened simultaneously. What is the maximum charge (in the unit of ( mu C ) ) on the ( 4 mu F ) capacitor? A ( cdot q_{0}=3 mu C ) В ( cdot q_{0}=6 mu C ) c. ( q_{0}=3.4 mu C ) D ( cdot q_{0}=6.8 mu C ) |
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| 164 | An inductance of ( 2 H ) carries a current of ( 2 A . ) To prevent sparking when the circuit is broken a capacitor of ( 4 mu F ) is connected across the inductance. The voltage rating of the capacitor is of the order of : B. ( 10 V ) ( mathbf{c} cdot 10^{5} V ) D. ( 10^{6} V ) |
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| 165 | Which of the following plots may represent the reactance of a series ( L C ) combination? ( 4 cdot(a) ) ( B .(b) ) ( c cdot(c) ) ( D cdot(d) ) |
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| 166 | The r.m.s. value of potential difference shown in the figure is : ( A cdot V_{0} / sqrt{3} ) в. ( V_{0} ) ( c cdot V_{0} / sqrt{2} ) D. ( V_{0} / 2 ) |
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| 167 | In A.C circuit having only capacitor, the current A ‘ lags behind the voltage by ( frac{pi}{2} ) in phase B. Ieads the voltage by ( frac{pi}{2} ) in phase c. leads the voltage by ( pi ) in phase D. lags behind the voltage by ( pi ) in phase |
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| 168 | 10 54. A simple LR circuit is connected to a battery at time t = 0. The energy stored in the inductor reaches half its maximum value at time – In |
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| 169 | In a series LCR circuit connected to an ac source of variable frequency and voltage ( boldsymbol{v}=boldsymbol{v}_{m} sin omega boldsymbol{t}, ) draw a plot showing the variation of current ( (boldsymbol{I}) ) with angular frequency ( (omega) ) for two different values of resistance ( boldsymbol{R}_{1} ) and ( boldsymbol{R}_{2} ) ( left(R_{1}>R_{2}right) . ) Write the condition under which the phenomenon of resonance occurs. For which value of the resistance out of the two curves a sharper resonance is produced? Define Q-factor of the circuit and give its significance. |
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| 170 | 62. In an LC circuit shown in figure, C = 1F, L=4 H. At time t=0, charge in the capacitor is 4 C and it is decreasing at the rate of 5 C s. Choose the correct statement. (a) Maximum charge in the capacitor can be 6 C (b) Maximum charge in the capacitor can be 8 C (c) Charge in the capacitor will be maximum after time 3 sin (2/3) s (d) None of these will |
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| 171 | The plot given below is of the average power delivered to an LRCLRC circuit versus frequency. The quality factor of the circuit is: A . 5.0 B. 2.0 ( c .2 .5 ) D. 0.4 |
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| 172 | In R-L-C series circuit, the potential differences across each element is ( 20 V ) Now the value of the resistance alone is doubled, then P.D. across ( mathrm{R} ), L and ( mathrm{C} ) respectively. A. ( 20 V, 10 V, 10 V ) В. ( 20 V, 20 V, 20 V ) c. ( 20 V, 40 V, 40 V ) D. ( 10 V, 20 V, 20 V ) |
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| 173 | In an oscillating ( L C ) circuit, the total stores energy is ( U ) and the maximum charge on the capacitor is ( Q . ) When the charge on the capacitor is ( Q / 2, ) the energy stored in the inductor is : A. ( U / 2 ) в. ( U / 4 ) c. ( (4 / 3) U ) D. ( 3 U / 4 ) |
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| 174 | A ( 100 % ) efficiency transformer has 100 turns in the primary and 25 turm coil. If the current in the secondary coil is ( 4 A ) then the current in the primary coil is ( A cdot 1 A ) B. 4 A ( c cdot 8 A ) D. 16 A |
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| 175 | In a series LCR circuit, the plot of ( boldsymbol{I}_{boldsymbol{m}} ) vs ( omega ) is shown in the figure. The bandwidth of this plot will be then A. Zero B. ( 0.1 mathrm{rads}^{-1} ) c. ( 0.2 r a d s^{-1} ) D. ( 0.4 mathrm{rads}^{-1} ) |
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| 176 | Explain the term ‘sharpness of resonance’ in ac circuit. | 12 |
| 177 | 59. In the circuit shown (figure), the cell is ideal. The coil has an inductance of 4 H and zero resistance. F is a fuse of zero resistance and will blow when the current through it reaches 5 A. The switch is closed at t = 0. The fuse will blow (a) almost at once (b) after 2 s E=2V (c) after 5 s (d) after 10 s |
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| 178 | A current source sends a current ( boldsymbol{I}- ) ( i_{0} cos (omega t) . ) when connected across an unknown load, it gives a voltage output of ( boldsymbol{v}=boldsymbol{v}_{0} sin [boldsymbol{omega} boldsymbol{t}+(boldsymbol{pi} / mathbf{4})] ) across that load. then the voltage across the current source may be brought in phase with the current through it by A. Connecting an inductor in series with the load B. Connecting a capacitor in series with the load c. connecting an inductor in parallel with the loadd D. connecting a capacitor in parallel with the load |
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| 179 | In Fig, initially the capacitor is charged to a potential of ( 5 mathrm{V} ) and then connected to position across the inductor at position 2. The maximum current flowing in the LC circuit when the capacitor is connected across the inductor is : ( mathbf{A} cdot 10 A ) B. ( 20 A ) c. ( 30 A ) D. None of these |
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| 180 | 49. A coil has an inductance of 0.7 H and is joined in series with a resistance of 220 2. When an alternating emf of 220 V at 50 cps is applied to it, then the wattless component of the current in the circuit is (take 0.711=2.2] (a) 5 A (b) 0.5 A (c) 0.7 A (d) 7A |
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| 181 | The voltage across ( boldsymbol{Q} ) is 7.60 ( mathbf{A} cdot 20 V ) B. ( frac{sqrt{1350}}{10} V ) c. ( 5.5 V ) D. ( frac{sqrt{9524}}{10} V ) |
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| 182 | A varying current in the transformer’s primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the A. iron core B. electromagnetic field C. secondary windings D. none of the above |
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| 183 | (u) 66. In the series circuit shown in the figure the voltmeter reading will be (all the meters are ideal): (a) 300 V (b) 200 V (c) 100 V (d) 600 V |
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| 184 | The natural frequency of an LC – circuit is 1,25,000 cycles per second. Then the capacitor ( C ) is replaced by another capacitor with a dielectric medium of dielectric constant k. In this case, the frequency decreases by ( 25 k H z . ) The value of k is: A . 3.0 B. 2. c. 1.56 D. 1.7 |
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| 185 | In a step up transformer, primary and secondary currents are ( 500 A ) and ( mathbf{1 0 0} A ). The ratio of the number of turns in the respective coil is A . 1: 5 B. 5: 1 c. 25: 1 D. 1: 25 |
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| 186 | The ratio of the peak current through the capacitor and supply is known-as: A. Resonance current B. Dynamic resistance c. Q-factor D. None of the above |
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| 187 | 5. In an oscillating LC circuit, the maximum charge in the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is (a) e SONO (AIEEE 2003) |
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| 188 | The capacitive reactance of ( 50 mu mathrm{F} ) capacitance at a frequency of ( 2 times 10^{3} ) ( mathrm{Hz} ) will be ( _{—-} Omega ) ( A cdot frac{2}{pi} ) B. ( frac{3}{pi} ) ( c cdot frac{4}{pi} ) ( D cdot frac{5}{5} ) |
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| 189 | The capacitive reactance in an ( A C ) circuit is A. effective resistance due to capacity B. effective wattage c. effective voltage D. None of these |
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| 190 | An inductive coil has resistance of 100Omega. When an ac signal of frequency 1000 ( H z ) is fed to the coil, the applied voltage leads the current by ( 45^{circ} . ) What is the inductance of the coil? ( mathbf{A} cdot 2 m H ) в. 3.3 тН c. ( 16 m H ) D. ( sqrt{5} ) m Н |
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| 191 | A transmitter transmits at a wavelength of ( 300 m . ) A condenser of capacitance ( 2.4 mu F ) is being used. The value of the inductance for the resonant circuit is approximately В . ( 10^{-6} ) Н ( mathrm{c} cdot 10^{-8} mathrm{H} ) D. ( 10^{-10} H ) |
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| 192 | The adjoining figure shows an ( boldsymbol{A C} ) circuit with resistance ( boldsymbol{R} ), inductance ( boldsymbol{L} ) and source voltage ( V_{s} . ) Then A. the source voltage ( V_{s}=72.8 mathrm{V} ) B. the phase angle between current and source voltage is ( tan ^{-1}(7 / 2) ) c. Both ( (a) ) and ( ( b ) ) are correct. D. Both ( (a) ) and ( (b) ) are wrong. |
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| 193 | The given graph shows volume with time in the source voltage and steady state current drawn by a series ( boldsymbol{B} boldsymbol{L} boldsymbol{C} ) circuit: Which of the following statements is/are correct? (a) Current lags the voltage. (b) Resistance in the circuit is ( 250 sqrt{Omega} ) (c) Reactance in the circuit is ( 250 Omega ) (d) Average power dissipation in the circuit is ( 20 sqrt{3 Omega} ) A. Only a ( B cdot a & b ) ( c cdot a, b & c ) D. All |
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| 194 | In the circuit shown in figure, key K is closed at t = 0, the current through the key at the instant t = 10″ In 2 sis 422 50 — 20 V EL=5 mH 522 ws HA 622 (a) 2 A (c) 2.5 A C = 0.1 mF (b) 3.5 A (d) 0 |
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| 195 | For a series LCR circuit at resonance, the statement which is not true is A. Peak energy stored by a capacitor = peak energy stored by an inductor B. Average power = apparent power C. Wattless current is zero D. Power factor is zero |
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| 196 | toppr Q Type your question_ ( mathbf{A} ) ( B ) ( c ) ( (c) ) ( D ) |
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| 197 | Equation of current flowing towards left in the inductor | 12 |
| 198 | The ratio of the secondary to the primary turns in a transformer is 3: 2 and the output power is ( P . ) Neglecting all power losses, the input power must be A ( cdot frac{2 P}{3} ) в. ( frac{3 P}{2} ) c. ( frac{P}{2} ) D. ( P ) |
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| 199 | (i) Name the transformer used in the power transmitting station of a power plant. (ii) What type of current is transmitted from the power station? (iii) At what voltage is this current available to our household? |
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| 200 | In an ideal parallel LC circuit, the capacitor is charged by connecting it to a DC source which is then disconnected The current in the circuit A. becomes zero instantaneously B. grows monotonically. c. decays monotonically. D. oscillates instantaneously |
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| 201 | maximum current that will flow in the circuit |
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| 202 | 19. In an ac circuit, the potential differences across an inductance and resistance joined in series are, respectively, 16 V and 20 V. The total potential difference across the circuit is (a) 20 V (b) 25.6 V (c) 31.9 V (d) 53.5 V |
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| 203 | An AC source is connected in parallel with an L-C-R circuit as shown. Let ( I_{S}, I_{L}, I_{C} ) and ( I_{R} ) denote the currents through and ( V_{S}, V_{L}, V_{C} ) and ( V_{R} ) voltages across the corresponding components. Then: A ( cdot I_{S}=I_{L}+I_{C}+I_{R} ) В. ( V_{S}=V_{L}+V_{C}+V_{R} ) ( mathbf{c} cdotleft(I_{L}, I_{C}, I_{R}right)<I_{S} ) D. ( I_{L}, I_{C} ) may be greater than ( I_{S} ) |
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| 204 | Assertion (A): More the turns more is the resistance Reason(R): Impedance of primary and secondary in a transformer is directly proportional to number of turns in the coils. A. Both Assertion and Reason are true and Reason is the correct explanation for Assertion B. Assertion and Reason are true but Reason is not the correct explanation for Assertion C. Assertion is true, Reason is false D. Assertion is false, Reason is true |
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| 205 | In the circle shown ( boldsymbol{L}=mathbf{1} boldsymbol{mu} boldsymbol{H}, boldsymbol{C}=mathbf{1} boldsymbol{mu} boldsymbol{F} ) and ( R=1 k Omega . ) They are connected in series with a.c. source ( V=V_{0} sin omega t ) as shown.Which of the following option is/are correct? This question has multiple correct options A. The frequency at which the current will be in the phase with the voltage is independent of ( R ) B. At ( omega sim 0 ) the current flowing through the circuitt becomes nearly zero C. ( A t omega>>10^{6} r a d . s^{-1}, ) the circuit behave like a capacitor D. The current will be in phase with the voltage if ( omega= ) ( 10^{4} r a d cdot s^{-1} ) |
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| 206 | A power transformer has 50 turns for primary and 300 turns for secondary. What is turns ratio? How much is secondary voltage with primary voltage of ( 230 V ? ) |
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| 207 | ( A 20 V, 750 mathrm{Hz} ) source is connected to a series combination of ( mathrm{R}=100 Omega, mathrm{C}=10 ) ( mu F ) and ( L=0.1803 H . ) Calculate the time in which resistance will get heated by ( 10^{circ} mathrm{C} . ) (If thermal capacity of the material ( =2 mathrm{J} /^{circ} mathrm{C} ) A. 328 sec B. 348 sec c. ( 3.48 mathrm{sec} ) D. ( 4.32 mathrm{sec} ) |
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| 208 | The impedance of a series L-C-R circuit in an AC circuit is A ( cdot sqrt{R+left(X_{L}-X_{C}right)} ) B . ( sqrt{R^{2}+left(X_{L}^{2}-X_{C}^{2}right)} ) ( c cdot c ) D. None of these |
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| 209 | In a series LCR circuit, resoanance frequency if half of the frequency of source. The nature of the circuit is A. Capacitive B. Resistive c. Inductive D. cannot be defined |
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| 210 | In AC circuit having only capacitor, the current A ( cdot ) Leads the voltage by ( frac{pi}{2} ) in phase B cdot Lags behind the voltage by ( frac{pi}{2} ) in phase C. Leads the voltage by ( pi ) in phase D. Lags behind the voltage by ( pi ) in phase |
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| 211 | In a circuit, ( L, C ) and ( R ) are connected in series with an alternating voltage source of frequency ( f ). The current leads the voltage by ( 45^{circ} . ) The value of ( C ) is : A ( frac{1}{pi f(2 pi f L+R)} ) в. ( frac{1}{pi f(2 pi f L-R)} ) c. ( frac{1}{2 pi f(2 pi f L+R)} ) D. ( frac{1}{2 pi f(2 pi f L-R)} ) |
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| 212 | The primary coil of a step-down transformer has number of turns A. more B. less c. same D. None of the above |
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| 213 | If the equations of alternating voltage and alternating current in an A.C. circuit ( operatorname{are} boldsymbol{E}=boldsymbol{E}_{0} sin omega boldsymbol{t} ) volt and ( boldsymbol{I}= ) ( I_{0} sin (omega t-pi / 2) ) ampere respectively. The power loss in the circuit will be A . zero в. ( frac{E_{0} I_{0}}{sqrt{2}} ) c. ( frac{E_{0} I_{0}}{2} ) D. ( frac{E I}{sqrt{2}} ) |
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| 214 | An ( L-C-R ) series circuit has a maximum current of ( 5 A . ) If ( L=0.5 H ) and ( C=8 mu F, ) then the angular frequency of ( boldsymbol{A} boldsymbol{C} ) voltage is : A. 500 rad/s B. 5000 rad/s c. 400 rad/s D. ( 250 mathrm{rad} / mathrm{s} ) |
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| 215 | When a coil is connected to a ( 100 mathrm{V} ) d supply. The current is 2 A. When the same coil is connected to a.c. source ( E=100 sqrt{2} sin omega t, ) the current is ( 1 A ) Find the inductive reactance used : |
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| 216 | 36. Which voltmeter will give zero reading at resonance? mH (a) V (c) và (b) V2 (d) None |
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| 217 | In an A.C. circuit, the current flowing in inductance is ( boldsymbol{I}=mathbf{5} sin (mathbf{1 0 0} boldsymbol{t}-boldsymbol{pi} / mathbf{2}) ) amperes and the potential difference is ( boldsymbol{V}=mathbf{2 0 0} sin (mathbf{1 0 0} boldsymbol{t}) . ) The power consumption is equal to A. 1000 watt B. 40 watt c. 20 watt D. zero |
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| 218 | Find the In the circuit shown in Fig, switch ( S_{1} ) was closed for a long time. At time ( t=0 ) the switch is opened. Angular frequency of oscillation of the charge on the capacitor: A ( cdot 100 operatorname{rad} s^{-1} ) B. 200 rads( ^{-1} ) c. 300 rads( ^{-1} ) D. 400 rads( ^{-1} ) |
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| 219 | State whether given statement is True or False A lower Q produces a narrower bandwidth. A. True B. False |
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| 220 | A transformer used to reduce the alternating voltage is : A. Step-up transformer B. Step-down transformer c. Both step-up and step-down transformers D. None of these |
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| 221 | A series ( L C R ) circuit is connected to a source of alternating emf ( 50 mathrm{V} ) and if the potential differences across inductor and capacitor are ( 90 mathrm{V} ) and ( 60 V ) respectively, the potential difference across resistor is: ( mathbf{A} cdot 400 V ) в. ( 40 V ) ( c .80 V ) D. ( 1600 V ) |
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| 222 | A sinusoidal voltage ( V=200 sin 314 t ) is appiled to a ( 10 Omega ) resistor. Find (i) rms voltage (ii) rms current and (iii) power dissipated as heat. |
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| 223 | In the circuit diagram shown, ( X_{C}= ) ( mathbf{1 0 0 Omega}, boldsymbol{X}_{L}=mathbf{2 0 0 Omega} & boldsymbol{R}=mathbf{1 0 0 Omega} . ) The effective current through the source is: ( A cdot 2 A ) B. ( 2 sqrt{2} A ) ( c cdot 0.5 mathrm{A} ) D. ( sqrt{0.4 A} ) |
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| 224 | 57. For an LCR series circuit with an ac source of angular frequency o, (a) circuit will be capacitive if o > (b) circuit will be inductive if m=- vec (c) power factor of circuit will be unity if capacitive reactance equals inductive reactance (d) current will be leading voltage if o >- VLC |
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| 225 | In a step up transformer A. ( N_{s}=N_{p} ) B. ( N_{s}N_{p} ) D. nothing can be said. |
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| 226 | Assertion When a current flows in the coil of a transformer then its core becomes hot. Reason The core of transformer is made of soft- |
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| 227 | In the transmission of power the voltage of power generated at the generating stations is stepped up from ( 11 mathrm{kV} ) to 132 kV before it is transmitted. Why? | 12 |
| 228 | are rixed at separatıon or ( boldsymbol{a} ) trom eacn other as shown. The area of each plate is A. Plate 1 is given charge ( +Q ) while plate 2 and 3 are neutral and are connected to each other through coil of inductances ( L ) and switch ( S . ) If resistance of all connected wires is neglected the maximum current flow, through coil after closing switch is ( left(boldsymbol{C}=varepsilon_{0} boldsymbol{A} / boldsymbol{d}right) ) (neglect fringe effect) A ( cdot frac{Q_{0}}{sqrt{L C}} ) в. ( frac{Q_{0}}{sqrt{2 L C}} ) c. ( frac{2 Q_{0}}{sqrt{L C}} ) D. ( frac{Q_{0}}{2 sqrt{L C}} ) |
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| 229 | A coil of inductance ( 0.50 H ) and resistance ( 100 Omega ) is connected to a ( 240 V, 50 H z ) ac supply. The maximum current in the coil is given as ( frac{x}{100} A ) Find ( x ) |
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| 230 | A series LCR circuit containing a resistance of ( 120 Omega ) has angular resonance frequency ( 4 times 10^{5} ) rad ( s^{-1} ) At resonance the voltage across the resistance and inductance are ( 60 mathrm{V} ) and ( 40 mathrm{V} ) respectively. The angular frequency at which current in the circuit lags the voltage by ( 45^{0} ) is A ( cdot 16 times 10^{5} ) rad ( s^{-1} ) B. ( 8 times 10^{5} ) rad ( s^{-1} ) C . ( 4 times 10^{5} ) rad ( s^{-1} ) D. ( 2 times 10^{5} ) rad ( s^{-1} ) |
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| 231 | A step up transformer operates on a ( 230 V ) line and supplies to a load ( 2 A ) The ratio of primary to secondary windings is ( 1: 25 . ) Determine the primary current. A . ( 8.8 A ) B . ( 12.5 A ) c. ( 25 A ) D. ( 50 A ) |
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| 232 | A capacitance of ( left(frac{10^{-3}}{2 pi}right) F ) and an inductance of ( left[frac{100}{pi}right] m H ) and ( a ) resistance of ( 10 Omega ) are connected in series with an AC voltage source of ( 220 V, 50 H z . ) The phase angle of the circuit is A . ( 60^{circ} ) B. ( 30^{circ} ) ( mathbf{c} cdot 45^{circ} ) D. ( 90^{circ} ) |
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| 233 | A ( 100 m H ) inductor, a ( 25 mu F ) capacitor and a ( 15 Omega ) resistor are connected in series to a ( 120 V, 50 H z ) ac source. Calculate (a) impedance of the circuit at resonance (b) current at resonance (c) resonant frequency A ( . ) (a) ( 16 Omega ) (b) ( 9 A ) (c) ( 100 H z ) ( z ) B. (a) ( 15 Omega ) (b) ( 8 A ) (с) ( 100 H z ) c. ( (text { a) } 15 Omega ) (b) ( 8 A ) (с) ( 120 H z ) D. (a) ( 15 Omega ) (b) ( 7 A ) (с) ( 100 H z ) |
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| 234 | Complete the following diagram in Fig. of a transformer and name the parts labelled ( A ) and ( B ). Name the part you have drawn to complete the diagram What is the material of this part ? Is this transformer a step-up or step-down ? Give reason. |
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| 235 | COLOCUPUOIO 44. An rms voltage of 110 V is applied across a series circuit having a resistance 11 2 and an impedance 22 12. The power consumed is (a) 275 W (b) 366 W (c) 550 W (d) 1100 W |
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| 236 | How is the e.m.f. across primary and secondary coils of a transformer related with the number of turns of coil in them? |
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| 237 | A ( 50 W, 100 V ) lamp is to be connected to an AC mains of ( 200 mathrm{V}, 50 mathrm{Hz} ). What capacitor is essential to be put in series with the lamp? A ( cdot frac{25}{sqrt{2}} mu F ) в. ( frac{50}{pi sqrt{3}} mu F ) c. ( frac{50}{sqrt{2}} mu F ) D. ( frac{100}{pi sqrt{3}} mu F ) |
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| 238 | A circuit operating at ( frac{360}{2 pi} mathrm{Hz} Omega ) contains a ( 1 mathrm{F} mu ) capacitor and a 20 resistor. The inductor must be added in series to make the phase angle for the circuit zero is A . 7.7 B. 10 c. ( 3.5 mathrm{H} ) D. 15 H |
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| 239 | Potential difference across capacitor of capacitance 3C when the current in the circuit is maximum is ( A cdot frac{3 V_{0}}{4} ) B. ( frac{V_{0}}{4} ) ( c cdot frac{5 V_{0}}{4} ) D. none of these |
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| 240 | Assertion: Faraday’s laws are consequences of conservation of energy Reason: In a purely resistive A.C. circuit the current lags behind the e.m.f. in phase A. If both assertion and reason are true but the reason is the correct explanation of assertion. B. If both assertion and reason are true but the reason is not the correct explanation of assertion c. If assertion is true but reason is false D. If both the assertion and reason are false. E. If reason is true but assertion is false |
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| 241 | In the shown circuit, ( boldsymbol{R}_{1}=mathbf{1 0 Omega}, boldsymbol{L}= ) ( frac{sqrt{3}}{10} H, R_{2}=20 Omega, C=frac{sqrt{3}}{2} ) milli farad and ( t ) is time in seconds. Then at the instant current through ( boldsymbol{R}_{1} boldsymbol{i} boldsymbol{s} mathbf{1} boldsymbol{0} sqrt{boldsymbol{2}} boldsymbol{A} ) find the current through resistor ( boldsymbol{R}_{2} ) in amperes. |
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| 242 | Comparing the L-C oscillations with the oscillations of a spring block system (force constant of spring ( =k ) and mass of the block ( =m ) ), the physical quantity ( m k ) is equal to : A . ( C L ) в. ( 1 / C L ) c. ( C / L ) D. ( L / C ) |
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| 243 | A resistor, an indicator and a capacitor are connected in series with a ( 120 mathrm{V}, 100 ) ( mathrm{Hz} ) ac source. Voltage leads the current by ( 35^{circ} ) in the circuit. If the resistance of the resistor is ( 10 Omega ) and the sum of inductive and capacitive reactance is ( 17 Omega, ) calculate the self-inductance of the inductor. |
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| 244 | The source frequency for which a ( 5 mu mathrm{F} ) capacitor has a reactance of ( 1000 Omega ) is A ( cdot frac{100}{pi} ) Hz в. ( frac{1000}{pi} ) Н ( z ) ( c .200 H z ) D. ( 5000 mathrm{Hz} ) |
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| 245 | What is the mechanical equivalent of spring constant ( mathrm{k} ) in ( mathrm{LC} ) oscillating circuit? A ( cdot frac{1}{L} ) в. ( frac{1}{C} ) c. ( frac{L}{C} ) D. ( frac{1}{L C} ) |
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| 246 | Find the maximum value of current when inductance of two henry is connected to ( 150 V, 50 ) cycle supply ( ^{mathrm{A}} cdot frac{3}{2 sqrt{2} A} ) B. ( frac{5}{2 sqrt{2} A} ) c. ( frac{6}{2 sqrt{2} A} ) D. ( frac{7}{2 sqrt{2} A} ) |
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| 247 | A ( 12 Omega ) resistor, a ( 40 mu F ) capacitor, and an ( 8 m H ) coil are in series across an ac source. The resonant frequency is A ( .28 .1 H z ) в. ( 281 mathrm{Hz} ) ( mathbf{c} cdot 2,810 H z ) D. ( 10 H z ) |
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| 248 | At resonance, the angle ( phi ) is A. B. ( frac{pi}{2} ) c. ( frac{pi}{6} ) D. zero |
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| 249 | The average power dissipated in a pure inductance is ( ^{mathbf{A}} cdot frac{1}{2}^{L I^{2}} ) B . ( L I^{2} ) c. ( L I^{2} / 4 ) D. zero |
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| 250 | If we increase the driving frequency in a circuit with a purely resistive load, then amplitude ( V_{R} ) A. remain in the same B. increase c. decrease D. none |
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| 251 | When ( 10 V, D C ) is applies across a coil current through it is ( 2.5 mathrm{A}, ) if ( 10 mathrm{V}, 50 mathrm{Hz} mathrm{A} ) C. is applied current reduces to 2 A. Calculate reluctance of the coil. |
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| 252 | In an ac circuit, ( mathrm{V} ) and I are given by ( boldsymbol{V}=mathbf{1 5 0} sin (mathbf{1 5 0} boldsymbol{t}) boldsymbol{V} boldsymbol{a n d} boldsymbol{I}= ) ( 150 sin left(150 t+frac{pi}{3}right) A ) The power dissipated in the circuit is A . ( 106 mathrm{w} ) B. 150 ( mathrm{w} ) c. ( 5625 mathrm{w} ) D. zero |
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| 253 | 19. A fully charged capacitor C with initial charge qo is connected to a coil of self inductance L at t = 0. The time at which the energy is stored equally between the electric and the magnetic fields is (a) VLC (b) JLC (c) 27 VLC (d) VLC (AIEEF 11) |
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| 254 | In the above circuit, ( C=frac{sqrt{3}}{2} mu F, R_{2}= ) ( 20 Omega, L=frac{sqrt{3}}{10} H ) and ( R_{1}=10 Omega . ) Current ( operatorname{in} L-R_{1} ) path is ( I_{1} ) and in ( C-R_{2} ) path it is ( I_{2} ). The voltage of ( A . C ) source is ( operatorname{given} operatorname{by} V=200 sqrt{2} sin (100 t) ) volts. The phase difference between ( I_{1} ) and ( I_{2} ) is A ( cdot 30 ) B . ( 0^{circ} ) ( c cdot 150 ) D. 60 |
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| 255 | 12. Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the e.m.f. of ac is increased, the effect on the value of the current will be (a) Increases in the first circuit and decreases in the other (b) Increases in both the circuits (c) Decreases in both the circuits (d) Decreases in the first circuit and increases in the other |
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| 256 | A radio can tune over the frequency range of a portion of MW broadcast band: ( (800 mathrm{kHz} text { to } 1200 mathrm{kHz} ) ). If its LC circuit has an effective inductance of ( 200 mu mathrm{H}, ) what must be the range of its variable capacitor? [Hint: For tuning, the natural frequency i.e., the frequency of free oscillations of the LC circuit should be equal to the frequency of the radiowave.] |
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| 257 | In series ( L-R ) circuit, ( X_{L}=R ). Now a capacitor with ( X_{C}=R ) added in series. New power factor: A. Same as initial B. ( frac{1}{sqrt{2}} ) times the initial c. ( frac{1}{2} ) times the initial D. ( sqrt{2} ) times the initial |
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| 258 | the maximum energy so 66. The natural frequency of the circuit shown in figure is – TH VLC 70 L Vzic llllll llllll (d) none of these Problems Based on Mixed Concepts |
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| 259 | A series LCR circuit is connected to an a.c. source of variable frequency. Draw a suitable phasor diagram to deduce the expressions for the amplitude of the current and phase angle. |
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| 260 | An LC circuit has ( L=5 mathrm{mH} ) and ( mathrm{C}=20 mu boldsymbol{F} ) ( boldsymbol{V}=mathbf{5} times mathbf{1 0}^{-3} ) coswt is supplied. ( boldsymbol{omega} ) is twice the resonant frequency. Find the maximum charge stored in the capacitor. A. 66.6 nc B. 11.3 nC c. 23.2 nc D. 33.3 nc |
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| 261 | The average half-cycle value of a sine wave with a ( 40 V ) peak is A . ( 25.48 V ) B . ( 6.37 V ) c. ( 14.14 V ) D. ( 50.96 V ) |
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| 262 | (a) The voltage leads the current by it 8. A direct current of 5 A is superimposed on an alternating current I=10 sin ot flowing through a wire. The effective value of the resulting current will be (a) (15/2) A (b) 53A (c) 5√5A (d) 15 A mont of uolueamnare is cuina ܘܘܘܘ |
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| 263 | A ( 300 Omega ) resistor, a ( 0.250 H ) inductor and a ( 8.00 mu F ) capacitor are in series with an ac source with voltage amplitude ( 120 V ) and angular frequency ( 400 r a d / s . ) Which of the following is/are correct? This question has multiple correct options A. Voltage amplitude across the resistor is ( 97.9 V ) B. Voltage amplitude across the inductor is ( 32.6 mathrm{V} ) c. voltage amplitude across the capacitor is ( 102 V ) D. Voltage amplitude across the resistor is ( 32.6 V ) |
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| 264 | 15. Using an ac voltmeter, the potential difference in the elec- trical line in a house is read to be 234 V. If the line fre- quency is known to be 50 cycles per second, the equation for the line voltage is (a) V= 165 sin(100 mt) (b) V = 331 sin(100 Tot) (c) V=220 sin(100 mt) (d) V = 440 sin(100 Tt) |
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| 265 | A ( 220 mathrm{V} ) main supply is connected to a resistance of ( 100 mathrm{k} Omega ). The effective current is? A. ( 2.2 mathrm{mA} ) B. ( 2.2 sqrt{2} mathrm{mA} ) c. ( frac{2.2}{sqrt{2}} mathrm{m} ) D. None of these |
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| 266 | In a step-down transform the turn ratio is 1: 2 and output power is ( 2.2 k W ). if output current is ( 10 A ) then the value of input voltage and input current: A. ( 100 V, 20 A ) в. ( 110 V, 10 A ) c. ( 440 V, 5 A ) D. ( 440 V, 20 A ) |
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| 267 | In a transformer, there are 10000 turns in the primary coil and 25000 turns in the secondary coil.An AC EMF ( e= ) ( 50 sin pi t ) is applied across primary coil ,find the peak EMF across the secondary coil in ideal conditions |
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| 268 | An ideal resistance ( R ), ideal inductance ( L, ) ideal capacitance ( C ) and ( A C ) volt meters ( V_{1}, V_{2}, V_{3} ) and ( V_{4} ) are connected to an AC source as shown. At resonance, A. Reading in ( V_{3}= ) reading in ( V_{1} ) B. Reading in ( V_{1}= ) reading in ( V_{2} ) c. Reading in ( V_{2}= ) reading in ( V_{4} ) D. Reading in ( V_{2}= ) reading in ( V ) |
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| 269 | A steady current of magnitude ( I ) and an ( A C ) current of peak value ( I ) are allowed to pass through identical resistor for the same time. The ratio of heat produced in the two resistors will be : A .2: 1 B. 1: 2 c. 1: 1 D. None of these |
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| 270 | Assertion According to Lenz Law, since the same magnetic flux passes through both the primary and secondary windings in an ideal transformer,a voltage is induced in each winding. Reason Voltage induced is same in both the windings, ideally. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion C. Assertion is incorrect but Reason is correct D. Both Assertion and Reason are incorrect |
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| 271 | The capacitor of an oscillatory circuit of negligible resistance is enclosed in a evacuated container. The frequency of the circuit is ( 150 mathrm{kHZ} ) and when the container is filled with a gas, the frequency changes by 100 HZ. The dielectric constant of the gas. ( A cdot 2 ) B. 1.53 c. 1.0012 D. 3 |
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| 272 | The given graphs (a) and (b) represent the variation of the opposition offered by the circuit element to the flow of alternating current, with frequency of the applied emf. Identify the circuit element corresponding to each graph. |
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| 273 | In a black box of unknown elements ( (boldsymbol{L} ) or ( R ) or any other combination), an ac voltage ( boldsymbol{E}=boldsymbol{E}_{0} sin (boldsymbol{omega} boldsymbol{t}+boldsymbol{phi}) ) is applied and current in the circuit was found to be ( boldsymbol{I}=boldsymbol{I}_{0} sin [boldsymbol{omega} boldsymbol{t}+boldsymbol{phi}+(boldsymbol{pi} / mathbf{4})] . ) Then the unknown elements in the box may be A. Only capacitor B. Inductor and resistor both c. Either capacitor, resistor, inductor or only capacito and resistor D. only resistor |
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| 274 | The potential difference across a ( 2 H ) inductor as a function of time is shown in figure. At time ( t=0, ) current is zero Current at ( t=2 ) second is: A . ( 1 A ) в. 3 А ( c cdot 4 A ) D. ( 5 A ) |
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| 275 | ( A 60 mathrm{W} / 120 mathrm{V} ) bulb is connected to a ( 240 / 60 mathrm{Hz} ) supply with an inductance in series. Find the value of inductance so that bulb gets correct voltage. A ( cdot frac{2.3}{pi} ) н в. ( 2 sqrt{3} ) н с. ( pi ) н D. ( frac{2 sqrt{3}}{pi} ) н |
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| 276 | In the given circuit, initially ( boldsymbol{K}_{mathbf{1}} ) is closed and ( K_{2} ) is open. Then ( K_{1} ) is opened and ( K_{2} ) is closed. If ( q_{1}^{prime} ) and ( q_{2}^{prime} ) are charges on ( C_{1} ) and ( C_{2} ) and ( V_{1} ) and ( V_{1} ) are the voltage respectively, then A. charge on ( C_{1} ) gets redistributed such that ( V_{1}=V_{2} ) B. charge on ( C_{1} ) gets redistributed such that ( q_{1}^{prime}=q_{2}^{prime} ) C. charge on ( C_{1} ) gets redistributed such that ( C_{1} V_{1}= ) ( C_{2} V_{2}=C_{1} V ) D. charge on ( C_{1} ) gets redistributed such that ( q_{1}^{prime}+q_{2}^{prime}=2 q ) |
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| 277 | A coil of inductance ( 0.1 mathrm{H} ) is connected to ( 50 V, 100 H z ) generator and current is found to be 0.5A. The potential difference across resistance of the coil is A . ( 15 v ) B. 20V c. ( 25 v ) D. 39V |
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| 278 | At resonance, what is the relation between impedance of a series ( L C R ) circuit and its resistance ( boldsymbol{R} ) ? |
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| 279 | What is meant by wattless component of the current? |
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| 280 | A capacitor ‘C’ is connected across a D.C. source, the reactance of capacitor will be A . ZERO в. Нाप्प c. Low D. INFINITE |
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| 281 | Which of the following rejector circuit (symbols have their usual meaning)? ( A ) B. ( c ) D. |
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| 282 | 60. A typical light dimmer used to dim the stage lights in a theatre consists of a variable induction for L (where inductance is adjustable between zero and Lmax) connected in series with a light bulb B as shown. The mains electrical supply is 220 V at 50 Hz, the light bulb is rated at 220 V, 1100 W. What Lmax is required if en the rate of energy dissipation in Bulb to mains the light bulb is to be varied by a factor of 5 from its upper limit of 1100 W? (a) 0.69 H (b) 0.28 H (c) 0.38 H (d) 0.56 H |
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| 283 | ILLUSTRATION 24.4 In the series circuit of the figure, suppose R= 300 12, L = 60 mH, C =0.50 uF, source amplitude is Eo = 50 V and 0 = 10,000 rad – Find the reactances XL and Xc, the impedance Z, the current amplitude 1o, the phase angle 0, and the voltage amplitude b across each circuit element. … Tid ative and conditive reactances are |
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| 284 | A waveform has a baseline of ( 3 V ), a duty cycle of ( 20 %, ) and an amplitude of ( 8 V ) The average voltage value is A . ( 4 V ) в. ( 4.6 V ) c. ( 1.6 V ) D. ( 11 V ) |
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| 285 | The phase difference between the applied emf and the line current in an anti resonant circuit at resonance is A ( cdot frac{pi}{2} ) radian B. ( pi ) radian c. ( frac{3 pi}{2} ) radian D. zero |
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| 286 | Assertion In series ( boldsymbol{L}-boldsymbol{C}-boldsymbol{R} boldsymbol{A} boldsymbol{C} ) circuit, current and voltage are in same phase at resonance. Reason In series ( boldsymbol{L}-boldsymbol{C}-boldsymbol{R} boldsymbol{A} boldsymbol{C} ) circuit, resonant frequency does not depend on the value of resistance. Hence current, at resonance, does not depend on resistance. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion C. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 287 | A ( 1.5 mu F ) capacitor is charged of ( 60 V ) The charging battery is then disconnected and a ( 15 mathrm{mH} ) coil is connected in series with the capacitor so that LC oscillations occurs. Assuming that the circuit contains no resistance. The maximum current in this coil shall be close to A . 1.4 A B. ( 1.2 A ) ( c .0 .8 A ) D. 0.6 A |
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| 288 | The capacitance of a capacitor whose reactance is ( 2.00 Omega ) at ( 50.0 H z ) is ( frac{x}{10} m F ) Find ( boldsymbol{x} ) | 12 |
| 289 | 1. The power factor of an AC circuit having resistance R and inductance L connected in series and an angular velocity o is R (6) (R² + w²L²) 1/2 R (d) – “(R² – w²L²) 1/2 (AIEEE 2002) |
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| 290 | A ( 15.0 mu F ) capacitor is connected to a ( 220 V, 50 H z ) source. Find the capacitive reactance and the current ( (mathrm{rms} text { and peak }) ) in the circuit. If the frequency is doubled, what happens to the capacitive reactance and the current? |
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| 291 | Of the following about capacitive reactance which is correct? A. The reactance of the capacitor is directly proportional to its ability to store charge B. Capacitive reactance is inversely proportional to the frequency of the current C . Capacitive reactance is measured in farad D. The reactance of a capacitor in an AC circuit is similar to the resistance of a capacitor in a DC circuit |
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| 292 | Define quality factor of resonance in series LCR circuit. |
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| 293 | In a purely resistive circuit: A . current lags behind the voltage by ( 90^{circ} ) B. current leads the voltage by ( 90^{circ} ) C . current can lag or lead the voltage by ( 90^{circ} ) D. current is in phase with the voltage |
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| 294 | ( A 750 H z, 20 V ) source is connected to a resistance of ( 100 Omega, ) an inductance of ( 0.1803 H ) and a capacitance of ( 10 mu F ) all in series. Calculate the time in which the resistance (thermal capacity ( left.2 J /^{o} Cright) ) will get heated by ( 10^{circ} mathrm{C} ). (lgnore radiation) A . 6.8 min B. 5.8 min c. 7.8 min D. 9.8 min |
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| 295 | Using the expressions for charge and current for L-C oscillator, explain L-C oscillations. | 12 |
| 296 | A wire carrying ( 5.0 V ) is applied to a primary coil of the transformer. The primary coil has 10 turns and the secondary coil has 20 turns. Find out the emf induced in the secondary coil? ( mathbf{A} cdot 0.50 V ) в. ( 5.0 V ) c. ( 10 V ) D. ( 50 V ) E . ( 100 V ) |
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| 297 | The self inductance of a choke coil is 10 mH. When it is connected with a 10 V D.C. source, then the loss of power is 20 watt. When it is connected with 10 volt A.C. source loss of power is 10 watt. The frequency of A.C. source will be. A . 50 нz в. 60 на c. 80 Нz D. 100 Н ( z ) |
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| 298 | In a series LCR circuit, resonance occurring at ( 105 mathrm{Hz} ). At that time, the potential difference across the 100 resistance is ( 40 mathrm{V} ) while the potential difference across the pure inductor is 30v. The inductance L of the inductor is equal to A ( cdot 2.0 times 10^{-4} ) B . ( 3.0 times 10^{-4} ) c. ( 1.2 times 10^{-4} ) D. ( 2.4 times 10^{-4} ) |
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| 299 | The equation of an alternating voltage is ( V=100 sqrt{2} sin 100 pi t ) volt. The RMS value of voltage and frequency will be respectively A. ( 100 V, 50 H z ) в. ( 50 V, 100 H z ) c. ( 150 V, 50 H z ) D. ( 200 V, 50 H z ) |
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| 300 | The frequency of an alternating potential is ( 50 H z ), then the time difference corresponding to a phase angle of ( 50^{circ} ) is A . 60 sec B. 1 sec c. ( (1 / 60) ) sec D. ( (1 / 360) ) sec |
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| 301 | toppr Q Type your question. obtain expressions for impedance of the circuit and phase angle between voltage and current. Find the condition when current will be in phase with the voltage. What is the circuit in this condition called? (ii) In a series LR circuit ( boldsymbol{X}_{L}=boldsymbol{R} ) and power factor of the circuit is ( P_{1} ). When capacitor with capacitance C such that ( X_{L}=X_{C} ) is put in series, the power factor becomes ( P_{2} ). Calculate ( P_{1} / P_{2} ) OR (i) Write the function of transformer. state its principle of working with the help of a diagram. Mention various energy losses in this device. (ii) The primary coil of an ideal step up transformer has 100 turns and transformation ratio is also ( 100 . ) The input voltage and power are respectively ( 220 mathrm{V} ) and ( 1100 mathrm{W} ). Calculate (a) number of turns in secondary (b) voltage across secondary (c) current in primary (d) current in secondary (e) power in secondary |
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| 302 | ILLUSTRATION 24.1 The plate on the back of a perso computer says that it draws 2.7 A from a 120-V, 60-HI For this computer, what is (a) the average of the square of the current, (b) the current amplitude, (c) the average current for positive half cycle, and (d) the average current for a full cycle Solution |
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| 303 | A condenser of ( 250 mu F ) is connected in parallel to a coil of inductance ( 0.16 mathrm{mH} ) while its effective resistance is ( 20 Omega ) Determine the resonant frequency. A ( cdot 9 times 10^{4} H z ) B . ( 16 times 10^{7} mathrm{Hz} ) c. ( 8 times 10^{5} H z ) ( mathbf{D} cdot 9 times 10^{3} H z ) |
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| 304 | Which of the following is correct for a step up transformer? ( mathbf{A} cdot N_{s}=N_{p} ) В. ( N_{s}N_{p} ) D. Nothing can be said |
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| 305 | 26. When 100 V dc is applied across a solenoid, a current of 1.0 A flows in it. When 100 V ac is applied across the same coil, the current drops to 0.5 A. If the frequency of the ac source is 50 Hz, the impedance and inductance of the solenoid are (a) 200 22 and 0.55 H (b) 100 22 and 0.86 H (c) 200 22 and 1.0 H (d) 100 22 and 0.93 H |
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| 306 | от России 56. In the circuit shown in the figure, Xc= 100 S2, XL = 200 S2 and R=100 2. The effective current through the source is M 200 v ) (a) 2 A (c) 0.5 A (b) 212 A (d) 10.4 A |
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| 307 | A transmitter transmits at a wave length of 300 meters. A capacitor of a capacitance ( 9.6 mu mathrm{F} ) is being used. The value of the inductance for the resonant circuit is approximately A . 2.5 ( mathrm{mH} ) в. 2.5 ( mu ) Н c. 2.5 n D. 2.5 ph |
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| 308 | ( ln ) an ( L C ) oscillation circuit, ( L= ) ( mathbf{1} boldsymbol{H}, boldsymbol{C}=frac{mathbf{1}}{mathbf{4}} boldsymbol{F} ) and maximum charge in capacitor is ( 4 C . ) Match the following two columns. Note that in column II all values are in their respective Sl units |
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| 309 | For an ideal step-down transformer, the quantity which is constant for both the coils will be A. current in the coils B. voltage across the coils c. resistance of coils D. power in the coils |
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| 310 | In an oscillating LC circuit the maximum charge on the capacitor is ( Q ) The charge on capacitor when the energy is stored equally between electric and magnetic field is : ( mathbf{A} cdot Q / 2 ) в. ( Q / sqrt{3} ) c. ( Q / sqrt{2} ) D. ( Q ) |
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| 311 | 21. A capacitor of 10 uF and an inductor of 1 H are joined in series. An ac of 50 Hz is applied to this combination. What is the impedance of the combination? (a) 5(17+ – 5), (b) 10(10–īt?), TT (c) 10(T? – 5), (d) 5(10–17?), |
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| 312 | An alternating voltage (in volts) given by ( V=200 sqrt{2} sin (100) t ) is connected to ( 1 mu F ) capacitor through an ideal ac ammeter in series. The reading of the ammeter and the average power consumed in the circuit shall be A ( .20 m A, 4 W ) в. ( 20 m A, 0 ) c. ( 20 sqrt{2} m A, 8 W ) D. ( 20 sqrt{2} mathrm{mA}, 4 sqrt{2} mathrm{W} ) |
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| 313 | When an ac source of voltage ( boldsymbol{V}= ) ( V_{0} sin 100 t ) is connected across a circuit, the phase difference between the voltage ( V ) and current lin the circuit is observed to be ( pi / 4, ) as shown in figure. If the circuit consists possibly only of RC or RL or LC in series, find possible values of two elements. A ( . R=1 k Omega, C=10 mu F ) B. ( R=1 k Omega, C=1 mu F ) c. ( R=1 k Omega, L=10 m H ) D. ( R=10 k Omega, L=10 m H ) |
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| 314 | The angular frequency of an AC source is 10 radian/sec. The reactance of ( 1 mu F ) capacitor will be A ( cdot 10^{4} Omega ) B . ( 10^{2} Omega ) ( mathbf{c} cdot 10^{1} Omega ) D. ( 10^{5} Omega ) |
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| 315 | A capacitor of capacitance ( C ) has initial charge ( Q_{0} ) and connected to an inductor of inductance ( L ) as shown. At ( t=0 ) switch S is closed. The current through the inductor when energy in the capacitor is three times the energy of inductor is A ( cdot frac{Q_{0}}{2 sqrt{L C}} ) в. ( frac{Q_{0}}{sqrt{L C}} ) c. ( frac{2 Q_{0}}{sqrt{L C}} ) D. ( frac{4 Q_{0}}{sqrt{L C}} ) |
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| 316 | In a purely resistive ( boldsymbol{A C} ) circuit A. voltage leads current B. voltage lags current C . voltage and current are in same phase D. nothing can be said |
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| 317 | In the given circuit ( R ) in pure resistance and ( X ) is unknown circuit element. An AC voltage source is applied across ( boldsymbol{A} ) and ( C . ) If ( V_{A B}=V_{A C}, ) then ( X ) is A. Pure resistance B. Pure inductance C. Combination of inductance and capacitance at resonance D. None of the above |
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| 318 | 9. Find out the amount of charge flown through the wire at seconds. (a) 3 coulombs (c) 1 coulomb (b) 6 coulombs (d) Zero coulomb |
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| 319 | If in a series L-C-R ac circuit, the voltages across ( L, C ) and ( R ) are ( V_{1}, V_{2} ) and ( V_{3} ) respectively, then the voltage of the source is always A. equal to ( V_{1}+V_{2}+V_{3} ) B. equal to ( V_{1}-V_{2}+V_{3} ) c. more than ( V_{1}+V_{2}+V_{3} ) D. none of the above is true |
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| 320 | ( ln L-C-R operatorname{series} ) circuit, the capacitor is changed from ( C ) to ( 4 C ). For the same resonant frequency, the inductance should be changed from ( boldsymbol{L} ) to A ( .2 L ) в. ( frac{L}{2} ) c. ( frac{L}{4} ) D. ( 4 L ) |
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| 321 | Obtain the relation ( boldsymbol{I}=boldsymbol{I}_{0} sin (boldsymbol{omega} boldsymbol{t}+boldsymbol{pi} / mathbf{2}) ) and ( X_{C}=1 / omega C ) for a pure capacitor across which an altering ( e m f=V= ) ( V_{0} sin omega t ) is applied. Draw a phasor diagram showing emf ( V ), current ( I ) and their phase difference ( phi ) |
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| 322 | A 220 volt input is supplied to a transformer. The output circuit of 2.0 ampere at 440 volts. If the efficiency of the transformer is ( 80 % ), the current drawn by the primary windings of the transformer is |
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| 323 | An inductor, a resistor and a capacitor are joined in series with an ( A C ) source. As the frequency of the source is slightly increased from a very low value, the reactance A. of the inductor increases B. of the resistor increases c. of the capacitor increases D. of the circuit increases |
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| 324 | The natural frequency ( left(omega_{0}right) ) of oscillations in LC Circuit is given by: A ( cdot frac{1}{2 pi} frac{1}{sqrt{L C}} ) B. ( frac{1}{pi} frac{1}{sqrt{2 L C}} ) c. ( frac{1}{sqrt{L C}} ) D. ( sqrt{L C} ) |
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| 325 | The current which does not contribute to the power consumed in an AC circuit is called: A. Non-ideal current B. Wattless current c. convectional current D. Inductance current |
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| 326 | In the given LCR series circuit. Choose the correct option/options (resistance is nonzero). A. Reading of Voltmeter ( V_{2} ) may be greater than source voltage B. Reading of voltmeter ( V_{4} ) may be equal to ( V_{1} ) C. Reading of ( V_{4} ) may be equal to source voltage ( v ) D. None of these |
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| 327 | In an LCR circuit, the capacitance is made one-fourth, when in resonance. Then what should be the change in inductance, so that the circuit remains in resonance? A. 4 times B. (1/4) times ( c .8 ) times D. 2 times |
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| 328 | Calculate resonant frequency and ( Q ) factor of a series L-C-R circuit containing a pure inductor of inductance ( 3 mathrm{H} ), Capacitor of capacitance ( 27 mu F ) and resistor of resistance ( 7.4 Omega ) |
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| 329 | What is ( Q ) -factor? Write its expression and write the conditions for its maximum value. |
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| 330 | The impedance of a pure anti-resonant circuit at resonance is A . zero B. infinity ( c cdot 1 ) D. ( frac{1}{2} ) |
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| 331 | An inductive circuit contains resistance of 10 ohms and an inductance of ( 20 mathrm{H} ). If an A.c voltage of 120 volt and frequency ( 60 mathrm{Hz} ) is applied to this circuit, the current would be nearly A. ( 0.16 a m p ) B. ( 0.3 a m p ) c. ( 0.48 a m p ) D. ( 0.80 a m p ) |
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| 332 | An alternating voltage of ( 220 V, 50 H z ) frequency is applied across a capacitor of capacitance ( 2 mu F ). The impedence of the circuit is: A ( frac{pi}{5000} ) в. ( frac{1000}{pi} ) ( c .500 pi ) D. ( frac{5000}{pi} ) |
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| 333 | A blackbox (BB) which may contain a combination of electrical circuit elements (resistor capacitor or inductor) is connected with other external circuit elements as shown below in the figure (a).After the switch(s) is closed at time ( t=0, ) the current (I) as a function of time (t) is shown in the figure (b). From this we can infer that the blackbox contains A. A resistor and a capacitor in series. B. A resistor and a capacitor in parallel. c. A resistor and an inductor in series D. A resistor and an inductorin parallel. |
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| 334 | The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of ( 20 vee, 50 mathrm{Hz} ) What will be the output of the secondary? A ( .200 vee, 50 ) Н ( z ) в. ( 100 vee, 50 ) Н ( z ) c. ( 200 vee, 500 ) Н ( z ) D. 250 V, 50 нz |
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| 335 | A box contains ( L, C ) and ( R ). When ( 250 V ) dc is applied to the terminals of the box, a current of ( 1.0 A ) flows in the circuit. When ac source of ( 250 mathrm{V} ) rms at ( 2250 r a d / s ) connected, a current of ( 1.25 A mathrm{rms} ) flows. It is observed that the current rises with frequency and becomes maximum at 4500 rad/s. Find the values of ( L, C ) and ( R . ) Draw the circuit diagram. |
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| 336 | Voltage ( V ) and current i in AC circuit is given by ( mathrm{V}=mathbf{5 0} sin (mathbf{5 0} t) ) volt ( mathrm{i}=50 sin left(50 t+frac{pi}{3}right) m A . ) The power dissipated in circuit is: ( mathbf{A} cdot 5.0 W ) B . ( 2.5 W ) c. ( 1.25 W ) D. zero |
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| 337 | In a transformer, the number of turns of primary coil and secondary coil are 5 and 4 respectively. If ( 220 mathrm{V} ) is applied on the primary coil, then the ratio of primary current to the secondary current is : A .4: 5 B. 5: 4 ( c cdot 5: 9 ) D. 9 : 5 |
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| 338 | A condenser of capacity ( C ) is charged to a potential difference of ( V_{1} . ) The plates of the condenser are the connected to an ideal inductor of inductance ( L ). The current through the inductor when the potential difference across the condenser reduces to ( V_{2} ) is ( ^{mathbf{A}} cdotleft(frac{Cleft(V_{1}^{2}-V_{2}^{2}right)}{L}right)^{1 / 2} ) ( ^{mathbf{B}} cdotleft(frac{Cleft(V_{1}-V_{2}right)}{L}right)^{1 / 2} ) ( ^{mathbf{C}} cdot frac{Cleft(V_{1}^{2}-V_{2}^{2}right)}{L} ) D. ( frac{Cleft(V_{1}-V_{2}right)}{L} ) |
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| 339 | An alternating voltage ( boldsymbol{V}=boldsymbol{V}_{0} sin omega boldsymbol{t} ) is applied across a circuit and as a result, a current ( boldsymbol{I}=boldsymbol{I}_{0} sin left(boldsymbol{omega} boldsymbol{t}+frac{boldsymbol{pi}}{2}right) ) flows in it The power consumed per cycle is A . ( I_{0} V_{0} ) в. ( 0.5 I_{0} V_{0} ) c. ( 0.7 I_{0} V_{0} ) D. ( 1.41 I_{0} V_{0} ) ( E . ) |
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| 340 | A capacitor of ( 20 mu F ) is connected in series with a ( 25 Omega ) resistance to a peak e.m.f ( 240 v, 50 H z ) A.c. Calculate (i)the capacitive reactance of the circuit. (ii)an impedance of the circuit |
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| 341 | The applied potential difference in the circuit shown is ( V=10 sin 100 t ) where ( V ) is in volt and ( t ) is in second. If the power factor of the circuit is ( frac{1}{sqrt{2}}, ) then the value of capacitance ( C ) of the circuit, nearly is: A. ( 111 mu F ) в. ( 333 mu F ) c. ( 222 mu F ) D. ( 444 mu F ) |
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| 342 | The instantaneous potential difference between points ( A ) and ( B ) is (Phase angle is ( left.37^{0}right) ) A ( cdot 8 sin left(50 pi t+37 frac{pi}{180}right) ) B. ( 8 sin left(50 pi t-37 frac{pi}{180}right) ) c. ( 10 sin (50 pi t) ) D. ( 10 cos (50 pi t) ) |
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| 343 | 4. In the above question the average value of voltage (V) in one time period will be (d) zero |
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| 344 | If the inductance ( L ) in an oscillating ( L C ) circuit having a given maximum charge ( Q ) is increased, then A. the current magnitude increases B. the maximum magnetic energy increases c. othere maximum magnetic energy decreases D. currentt magnitude and maximum magnetic energy remain constant |
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| 345 | The diagram given show the variation of voltage and current in an AC circuit. The circuit contains A. Only a resistor B. Only a pure inductor c. Only a capcacitor D. A capacitor and and inductor |
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| 346 | Rms value of current ( boldsymbol{i}=mathbf{3}+ ) ( 4 sin left(omega t+frac{pi}{3}right) ) is: A . ( 5 A ) в. ( sqrt{17} A ) ( c cdot frac{5}{sqrt{2}} A ) D. ( frac{7}{sqrt{2}} A ) |
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| 347 | The voltage and the current of an a.c circuit are ( V=100 sin (100 t) ) volt and ( boldsymbol{i}=mathbf{1 0 0} sin (mathbf{1 0 0} boldsymbol{t}+boldsymbol{pi} / mathbf{3}) boldsymbol{m} boldsymbol{A} ) receptively. The power dissipated in the circuit is: A ( cdot 10^{4} W ) в. ( 10 W ) c. ( 2.5 W ) D. ( 5.0 W ) |
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| 348 | An ( L C R ) circuit has ( L=10 m H, R= ) ( 150 Omega ) and ( C=1 mu F ) connected in series to a source of ( 150 sqrt{2} ) cos ( omega t ) volt. At a frequency that is ( 50 % ) of the resonant frequency, calculate the average power (in ( boldsymbol{w} boldsymbol{a} boldsymbol{t} boldsymbol{t} ) ) dissipated per cycle. |
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| 349 | For an ( L-R ) circuit, the inductive reactance is equal to the resistance ( boldsymbol{R} ) of the circuit. An emf ( boldsymbol{E}=boldsymbol{E}_{0} cos (boldsymbol{w} boldsymbol{t}) ) is applied to the circuit. Then, the power consumed in the circuit is : A ( cdot frac{E_{0}}{R} ) в. ( frac{E_{0}^{2}}{4 R} ) c. ( frac{4 R}{E_{0}} ) D. ( frac{R}{E_{0}} ) |
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| 350 | In LC oscillation resistance is ( 100 Omega ) and inductance and capacitance is ( 1 mathrm{H} ) and 10 ( mu F ). Find the half power of frequency. ( mathbf{A} cdot 266.2 ) B. 366.2 c. 166.2 D. 233.2 |
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| 351 | In the given circuit find out : (i) maximum value of current in the circuit, (ii) root mean square value of current in the circuit, |
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| 352 | In L-C-R circuit power of 3 mH inductance and ( 4 Omega ) resistance, EMF ( boldsymbol{E}=mathbf{4} cos mathbf{1 0 0 0} boldsymbol{t} ) volt is applied. The amplitude of current is A ( .0 .8 AA ) в. ( frac{4}{7} ) c. ( 1.0 dot{A} ) D. ( frac{4}{sqrt{7}} dot{A} ) |
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| 353 | An arc lamp requires a direct current of ( 10 A ) at ( 80 mathrm{V} ) to function. If it is connected to a ( 220 mathrm{V}(mathrm{rms}), 50 mathrm{Hz} ) AC supply, the series inductor needed for it to work is close to: A . 80H B. 0.08H c. 0.0444 D. 0.065H |
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| 354 | ( ln operatorname{an} L C R ) circuit as shown in figure, both switches are open initially. Now switch ( S_{1} ) is closed, ( S_{2} ) kept open. ( (q ) is charge on the capacitor and ( 4 tau=R C ) is capacity time constant). Which of the following statement is correct? A ( cdot operatorname{At} t=frac{tau}{2}, q=C Vleft(1-e^{-1}right. ) B. Work done by the battery is half of the energy dissipated in the resistor c. At ( t=tau, q=C V / 2 ) D. At ( t=2 tau . q=C Vleft(1-e^{-2}right) ) |
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| 355 | 6. An A.C. is given by equation I=1, cos Ot+I sin ot. The r.m.s. value of current is given by (d) 1} +1 |
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| 356 | Give two point of difference between a step-up transformer and a step-down transformer? | 12 |
| 357 | If the reactance of a choke coil is ( X_{L} ) and its resistance is ( R ) then A. ( X_{L}=R ) в. ( X_{L}>>R ) c. ( x_{L}<<R ) D. ( X_{L}=alpha ) |
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| 358 | In the A.C. circuit shown, keeping’ ( boldsymbol{K} ) pressed, if an iron rod is inserted into the coil, the bulb in the circuit A. Gets damaged B. Glows less brightly c. Glows with same brightness (as before the rod is inserted D. Glows more brightly |
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| 359 | In a series LCR circuit connected to an a.c. source of voltage ( boldsymbol{v}=boldsymbol{v}_{m} sin omega boldsymbol{t} ) use phasor diagram to derive an expression for the current in the circuit. Hence, obtain the expression for the power dissipated in the circuit. Show that power dissipated at resonance is maximum. |
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| 360 | Q Type your question capacitor is ( 6 m F ) and is decreasing at the constant rate ( 0.5 m F s^{-1} . ) The potential difference across the capacitor at the shown moment is changing as follows ( frac{boldsymbol{d} boldsymbol{V}}{boldsymbol{d} boldsymbol{t}}=boldsymbol{2} boldsymbol{V} boldsymbol{s}^{-1} ) ( frac{boldsymbol{d}^{2} boldsymbol{V}}{boldsymbol{d t}^{2}}=frac{1}{2} boldsymbol{V} boldsymbol{s}^{-2} ) and the current in the ( 4 Omega ) resistor is decreasing at the rate of ( 1 m A s^{-1} . ) What is the potential difference (in ( m V) ) across the inductor at this moment? ( A cdot 4 ) B. 3 ( c cdot 8 ) ( D ) |
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| 361 | In series LCR circuit, the phase difference between applied voltage and current is A. Positive when ( X_{L}>X_{C} ) B. Positive when ( X_{C}>X_{L} ) ( c cdot 90^{circ} ) D. 0 |
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| 362 | In the circuit shown here, the ammeter ( A ) reads ( 5 A ) and the voltmeter ( V ) reads 20V.Find the correct value of resistance |
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| 363 | Assertion A step up transformer can also be used as a step down transformer Reason This is because ( frac{boldsymbol{E}_{boldsymbol{p}}}{boldsymbol{E}_{boldsymbol{s}}}=frac{boldsymbol{n}_{boldsymbol{s}}}{boldsymbol{n}_{boldsymbol{p}}} ) A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Assertion is incorrect but Reason is correct |
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| 364 | In an oscillating system, a restoring force is a must. In an ( L-C ) circuit, restoring force is provide by A. Capacitor B. Inductance c. Resistance D. Both (A) and (B) |
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| 365 | The reactance of a condenser of capacity ( 50 mu mathrm{F} ) for an ( A C ) of frequency ( 2 times 10^{3} ) Hertz will be ( A .5 ) ohm B. ( frac{2}{pi} ) ( c cdot frac{3}{pi} ) D. ( frac{5}{pi} ) |
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| 366 | In an a.c. circuit, the instantaneous e.m.f. and current are given by ( e= ) ( mathbf{1 0 0} sin mathbf{3 0} t, boldsymbol{i}=mathbf{2 0} sin left(mathbf{3 0} boldsymbol{t}-frac{boldsymbol{pi}}{mathbf{4}}right) . ) In one cycle of a.c., the average power consumed by the circuit and the wattles current are, respectively. A ( cdot frac{50}{sqrt{2}}, 0 ) в. 50,0 c. 50,10 D. ( frac{1000}{sqrt{2}}, 10 ) |
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| 367 | In a transformer, number of turns in primary and secondary are 500 and 2000 respectively. If current in primary is ( 48 mathrm{A} ), current in the secondary is : ( A cdot 144 A ) B. 24 A ( c cdot 48 A ) D. 12 A |
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| 368 | In a series RLC circuit, the r.m.s. the voltage across the resistor and the inductor are respectively ( 400 mathrm{V} ) and ( 700 V . ) If the equation for the applied voltage is ( varepsilon=500 sqrt{2} sin omega t, ) then the peak voltage across the capacitor is B. ( 400 sqrt{2} V ) c. ( 400 V ) D. ( 1200 sqrt{2} mathrm{V} ) |
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| 369 | The frequency of the output signal becomes ( _{-}–_{-}-_{-}- ) times by doubling the value of the capacitance in the LC oscillator circuit. A ( cdot sqrt{2} ) B. ( frac{1}{sqrt{2}} ) ( c cdot frac{1}{2} ) D. 2 |
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| 370 | toppr 5 Q Type your question_ ( mathbf{A} ) Reactance ( B ) Reactance ( c ) Reactance D. Reactance |
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| 371 | In a LR circuit of 3 m ( H ) inductane and ( 4 Omega ) resistance, emf ( E=4 cos (1000 t) ) volt is applied. The amplitude of current is: ( mathbf{A} cdot 0.8 A ) B. ( frac{4}{7} ) c. ( 1.0 A ) D. ( frac{4}{sqrt{7}} A ) |
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| 372 | A mixer of ( 100 Omega ) resistance is connected to an A.C. source of ( 200 mathrm{V} ) and 50 cycles/sec. The value of average potential difference across the mixer will be: ( A cdot 308 V ) B. 264 c. 220 D. zero |
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| 373 | In an L-C-R a.c. circuit at resonance, the current: A. is always in phase with the voltage B. always leads the voltage C . always lags behind the voltage D. may lead or lag behind the voltage |
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| 374 | 47. In the above question, the capacitive reactance in the circuit is (a) 100 12 (b) 25 122 (c) V125 x 75 2 (d) 400 40 TL 1 tinha |
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| 375 | A series LCR circuit with ( mathrm{R}=22 Omega, mathrm{L}=1.5 ) ( mathrm{H} ) and ( mathrm{C}=40 mu mathrm{F} ) is connected to a variable frequency ( 220 mathrm{V} ) ac supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle? A. 2000 B. 2200 W c. 2400 ( w ) D. 2500 W |
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| 376 | Assertion Peak value of current in ( boldsymbol{A} boldsymbol{C} ) through a resistance of ( 10 Omega ) is ( 2 A ). Then power consumed by the resistance should be ( mathbf{2 0} boldsymbol{W} ) Reason Power in ( boldsymbol{A C} ) is ( boldsymbol{P}=boldsymbol{I}_{r m s}^{2} boldsymbol{R} ) A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 377 | 2.5 FuF capacitor and 3000-ohm resistance are joined in TT series to an ac source of 200 volt and 50 sec frequency. The power factor of the circuit and the power dissipated in it will respectively (a) 0.6, 0.06 W (b) 0.06, 0.6 W (c) 0.6, 4.8 W (d) 4.8, 0.6 W |
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| 378 | The square root of the product of inductance and capacitance has dimensions of A . length B. mass ( c . ) time D. dimensionless |
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| 379 | Let ( ell, r, c ) and ( v ) represent inductance, resistance, capacitance and voltage, respectively. The dimension of ( frac{ell}{r c v} ) is SI units will be: A. ( [L T A] ) B . ( left[L A^{-2}right] ) ( mathbf{c} cdotleft[A^{-1}right] ) D cdot ( left[L T^{2}right] ) |
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| 380 | ( ln ) an oscillating ( L C ) circuit the maximum charge on the capacitor is ( Q ) The charge on the capacitor when the energy is stored equally between the electric and magnetic field is ( mathbf{A} cdot Q / 2 ) в. ( Q / sqrt{3} ) c. ( Q / sqrt{2} ) D. ( Q ) |
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| 381 | (C) 2.0 X10S (d) 2.5 x 10’s 18. An inductive coil has resistance of 100 12. When an ac signal of frequency 1000 Hz is fed to the coil, the applied voltage leads the current by 45°. What is the inductance of the coil? (a) 2 mH (b) 3.3 mH (c) 16 mH (d) V5 mH I . 1 |
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| 382 | Assertion The capacitive reactance limits the amplitude of the current in a purely capacitive circuit Reason Capacitive reactance is proportional to the frequency and the capacitance A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 383 | When the frequency of the AC voltage applied to series LCR circuit is gradually increased from a low value, the impedance of the circuit: A. monotonically increases. B. first increases and then decreases. c. first decreases and then increases. D. monotonically decreases |
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| 384 | A ( 200 F ) capacitor is initially charged to ( 20 V ) and then shorted across a ( 5 m H ) inductor. The angular frequency of oscillation is A. 1000 rad( / )s B. 100 rad( / )s c. 10000 rad( / )s D. ( 1 r a d / s ) |
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| 385 | Figure shows a series LCR circuit connected to a variable frequency 230 V source. ( L=5.0 mathrm{H}, mathrm{C}=80 mu mathrm{F}, mathrm{R}=40 Omega ) (a) Determine the source frequency which drives the circuit in resonance. (b) Obtain the impedance of the circuit and the amplitude of current at the resonating frequency. (c) Determine the rms potential drops across the three elements of the circuit. Show that the potential drop across the LC combination is zero at the resonating frequency. |
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| 386 | Assertion: The resistance offered by an inductor in a d.c circuit is always constant. Reason : The resistance of inductor in steady state is non-zero. A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion. B. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion. c. If Assertion is true statement but Reason is false D. If both Assertion and Reason are false statements |
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| 387 | An alternating voltage source is connected in an ( A C ) circuit whose maximum value is 170 volt. The value of potential at a phase angle of ( 45^{circ} ) will be A . 120.56 volt B. 110.12 Volt c. 240 volt D. zero |
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| 388 | A step up transformer is used to: A. increase the current and increase the voltage B. decrease the current and increase the voltage C. increase the current and decrease the voltage D. decrease the current and decrease the voltage |
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| 389 | A transformer is used to light a 140 watt, 24 volt lamp from ( 240 V ) AC mains. The current in the main cable is 0.7 amp. The efficiency of the transformer is A . ( 48 % ) B . ( 63.8 % ) c. ( 83.3 % ) D. 90% |
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| 390 | In a transformer the output current and voltage are ( 4 mathrm{A} ) and ( 20 mathrm{V} ) respectively. If the ratio of number of turns in the primary and secondary coil is 2: 1 respectively, what is the input current and voltage? ( A cdot 2 A ) and 40 B. 1 A and 20 c. 4 A and ( 10 v ) D. 8 A and 40 v |
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| 391 | Adjoining figure shows a series ( R C L ) circuit connected to an ac source which generates an alternating emf of frequency ( 50 H z . ) The reading of the voltmeters ( V_{1} ) and ( V_{2} ) are ( 80 V ) and ( 60 V ) respectively Find: The current in the circuit |
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| 392 | A series LCR circuit with ( R=20 Omega, L=1.5 ) ( mathrm{H} ) and ( mathrm{C}=35 mu mathrm{F} ) is connected to a variable-frequency ( 200 mathrm{V} ) ac supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle? |
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| 393 | In a certain loaded transformer, the secondary voltage is one-fourth the primary voltage. The secondary current is A. one-fourth the primary current B. four times the primary current c. equal to the primary current D. one-fourth the primary current and equal to the primary current |
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| 394 | In series LCR circuit ( R=18 Omega ) and impedance is ( 33 Omega ). An r.m.s. voltage ( 220 V ) is applied across the circuit. The true power consumed in a.c. circuit is A . ( 200 W ) в. ( 400 mathrm{W} ) c. ( 600 W ) D. ( 800 W ) |
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| 395 | ( boldsymbol{I}=boldsymbol{6} cos boldsymbol{w} boldsymbol{t}+boldsymbol{8} sin boldsymbol{w} boldsymbol{t} ) is applied across a resistor of ( 40 Omega ). Find the potential difference across the resistor A . ( 660 v ) B. 80 c. ( 330 v ) D. 400 |
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| 396 | An ( A C ) source rated ( 100 vee(r m s) ) supplies a current of ( 10 mathrm{A}(mathrm{rm} s) ) to a circiut. The average power delivered by the source. This question has multiple correct options A. must be ( 1000 mathrm{w} ) B. may be ( 1000 mathrm{w} ) c. may be greater than 1000 w D. may be less than 1000 w |
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| 397 | The angular frequency for which he detects maximum current in the circuit is ( mathbf{A} cdot 10^{5} / 7 r a d / s ) B . ( 10^{4} r a d / s ) c. ( 10^{5} r a d / s ) D. ( 10^{4} / 7 r a d / s ) |
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| 398 | A condenser and a ( 30 Omega ) resistance are connected in series. When they are connected to 120 V A.C. source then the current flowing in the circuit is 1A The p.d. across the ends of the condenser will be nearly ( A cdot 1 v ) B. 116 ( v ) c. zero D. 220 |
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| 399 | Find the current passing through battery immediately after key ( ( K ) ) is closed. It is given that initially all the capacitors are uncharged (Given that ( R=6 Omega text { and } C=4 mu F) ) ( A cdot 1 A ) ( c .3 A ) 0.24 |
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| 400 | An LCR series circuit with ( 100 Omega ) resistance is connected to an ac source of ( 200 mathrm{V} ) and of frequency of ( 300 mathrm{rad} / mathrm{s} ) When only the capacitance is removed, the current lags behind the voltage by ( 60^{0} . ) When only the inductance is removed, the current leads the voltage by ( 60^{0} ) the current through the circuit is: ( A cdot 1 A ) B. 2 A ( c cdot 3 A ) D. ( 4 mathrm{A} ) |
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| 401 | Inductive resistance ( 25 Omega ) and capacitive resistance ( 75 Omega ) are connected across ( 250 V ) mains in series. Find the rms potential difference across inductor and capacitor. |
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| 402 | What is the coefficient of coupling for a transformer in which ( 4 % ) of the total flux generated in the primary does not pass through the secondary? A . 0.4 B. 4 ( c .9 .6 ) D. 0.96 |
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| 403 | 7. The variation of the instantaneous current (1) and the instantaneous emf (E) in a circuit is as o 702_ 3102 shown in figure Which of the following statements is correct? (a) The voltage lags behind the current by rd2 (b) The voltage leads the current by ru2 (c) The voltage and the current are in phase (d) The voltage leads the current by |
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| 404 | The maximum current flowing long time after the switch ( mathrm{S} ) is moved to ( mathrm{B} ) should be A. 0.707 A B. 1.0 ( A ) ( c cdot 0.5 mathrm{A} ) D. 1.414 A |
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| 405 | A capacitor is connected to an A.C. circuit, then the phase difference between current and the voltage is : A . ( pi ) в. c. ( frac{-pi}{2} ) D. zero |
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| 406 | Can the phenomenon of resonance be exhibited in RL or RC circuit? |
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| 407 | ( ln ) an ( A C ) circuit, the potential difference ( boldsymbol{V} ) and current ( boldsymbol{I} ) are given respectively by ( boldsymbol{V}=mathbf{1 0 0} sin (mathbf{1 0 0} boldsymbol{t}) boldsymbol{V} ) and ( boldsymbol{I}=mathbf{1 0 0} sin left(mathbf{1 0 0 t}+frac{boldsymbol{pi}}{mathbf{3}}right) boldsymbol{m} boldsymbol{A} ) The power dissipated in the circuit will be A ( cdot 10^{4} K W ) в. ( 10 K W ) c. ( 2.5 K W ) D. ( 5 K W ) |
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| 408 | A power transmission line feeds input power at ( 2400 mathrm{V} ) to a step down transformer with its primary winding having 4000 turns. What should be the number of turns in the secondary winding in order to get output power at ( 240 vee ? ) A . 400 B. 420 ( c cdot 424 ) D. 436 |
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| 409 | Find the amplitude response ( left|frac{V_{2}}{V_{1}}right| ) for the circuit shown in figure. Determine the half-power frequency. A ( cdot frac{1}{R C} ) B. ( frac{sqrt{2}}{R C} ) ( c cdot frac{sqrt{3}}{B C} ) D. ( frac{2}{R C} ) |
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| 410 | An inductor of reactance ( X_{L}=4 Omega ) and resistor of resistance ( boldsymbol{R}=mathbf{3} Omega ) are connected in series with a voltage source of emf ( varepsilon= ) ( (20 V)[sin (100 pi r a d / s) t] . ) The current in the circuit at any time t will be? A ( cdot I=(4 A)left[sin (100 pi r a d / s) t+37^{circ}right] ) B . ( I=(4 A)left[sin (100 pi r a d / s) t-37^{circ}right. ) C ( cdot I=(4 A)left[sin (100 pi r a d / s) t+53^{circ}right. ) D. ( I=(4 A)left[sin (100 pi r a d / s) t-53^{circ}right. ) |
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| 411 | In the following circuit the values of ( boldsymbol{L}, boldsymbol{C}, boldsymbol{R} ) and ( boldsymbol{E}_{mathbf{0}} ) are ( 0.01 mathrm{H}, mathbf{1 0}^{-mathbf{5}} boldsymbol{F}, mathbf{2 5 Omega} ) and 220 volt respectively. The value of current flowing in the circuit at ( boldsymbol{f}=mathbf{0} ) and ( boldsymbol{f}=infty ) will respectively be ( A cdot 8 A ) and ( 0 A ) B. ( 0 A ) and ( 0 A ) ( c cdot 8 A ) and ( 8 A ) D. o ( A ) and ( 8 A ) |
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| 412 | The power loss is less in transmission lines, when : A. Voltage is less but current is more B. Both voltage and current are more c. Voltage is more but current is less D. Both voltage and current are less |
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| 413 | 16. For an RLC circuit driven with voltage of amplitude Vm and frequency 0= true. The quality factor, Q is given (6) WL R (d) R (0,0) (JEE Main 2018) |
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| 414 | An inductor, a resistor and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance of the A. inductor increases B. resistor increases c. capacitor increases D. circuit increases |
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| 415 | 0000000 WWW 12. An inductor (L = 100 mH), a resistor (R = 100 2), and a battery (E = 100 V) are initially connected in series as shown in the figure. After a long time the battery is disconnected after short circuiting the points A and B. The current in the circuit 1 mm after the short circuit is (a) 0.1 A (b) 1A (c) A (d) e A (AIEEE 2006) |
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| 416 | A. ( C . ) supply gives ( 30 V ) r.m.s. which passes through a ( 10 Omega ) resistance. The power dissipated in it is : B. ( 90 W ) c. ( 45 sqrt{2} mathrm{W} ) D. ( 45 W ) |
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| 417 | A capacitor of capacitance ( C ) has initial charge ( Q_{0} ) and connected to an inductance ( L . ) At ( t=0 ) switch ( S ) is closed. The current through the inductor when energy in the capacitor is three times the energy of the inductor is : A ( cdot frac{Q_{0}}{2 sqrt{L C}} ) в. ( frac{Q_{0}}{sqrt{L C}} ) c. ( frac{2 Q_{0}}{sqrt{L C}} ) D. ( frac{4 Q_{0}}{sqrt{L C}} ) |
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| 418 | An LC circuit contains a ( 40 mathrm{mH} ) inductor and a ( 25 mu ) F capacitor. The resistance of the circuit is negligible. The time is measured from the instant the circuit is closed. The energy stored in the circuit is completely magnetic at times (in milliseconds) A . 0,3.14,6.28 B. 0, 1.57, 4.71 c. 1.57,4.71,7.85 D. 1.57, 3.14, 4.71 |
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| 419 | The output power in a step-up transformer is A. Greater than the input power B. Equal to the input power C. Maintained even during the power cut D. Less than the input power |
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| 420 | Name one source each of D.C and A.C. | 12 |
| 421 | In the given circuit initially the charge on capacitor is ( Q_{0} ) At ( t=0 ) the switch ( S ) is closed Which of the following statement(s) is/are correct? This question has multiple correct options A . Maximum current through the inductor is ( frac{Q_{0}}{sqrt{L C}} ) B. charge on the capacitor is zero at ( t=frac{pi}{2} sqrt{L C} ) C. Current through the inductor is maximum at ( t= ) ( frac{pi}{2} sqrt{L C} ) D. Maximum magnetic energy can be stored in the inductor is ( frac{Q_{0}^{2}}{2 C C} ) |
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| 422 | In a pure capacitive A.C circuit current and voltage differ in phase by A ( cdot 0^{circ} ) B . ( 45^{circ} ) ( mathrm{c} cdot 90^{circ} ) D. ( 180^{circ} ) |
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| 423 | Time is closed at t = 0. 52. Switch S of the circuit shown in figure is closed at If e denotes the induced emf in L and i the current flowing through the cir- cuit at time 1, then which of the following graphs W correctly represents the 2000- variation of e with i? |
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| 424 | A condenser of capacity ( 20 mu F ) is first charged and then discharged through a 10 ( m H ) inductance. Neglecting the resistance of the coil, the frequency of the resulting vibrations will be A. 356 cycle/s B. 35.6 cycle/s ( mathbf{c} cdot 356 times 10^{3} ) cycle ( / mathrm{s} ) D. 3.56 cycle/s |
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| 425 | The ( Q ) factor of a series LCR circuit with ( mathrm{L}=2 mathrm{H}, mathrm{C}=32 mu mathrm{F} ) and ( mathrm{R}=10 Omega mathrm{is} ) A . 15 B. 20 ( c cdot 25 ) D. 30 |
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| 426 | Answer the following: What is the impedance of a capacitor of capacitance ( C ) in an ( A C ) circuit using source of frequency n Hz? |
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| 427 | 29. For the circuit shown in the figure, current in inductance is 0.8 A while that in capacitance is 0.6 A. What is the current drawn from the source? (a) 0.1 A (b) 0.3 A (c) 0.6 A (d) 0.2 A |
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| 428 | In a primary coil 5 A current is flowing on 220 volts. In a primary coil 5 A current is flowing on 220 volts. the ratio of number of turns in secondary coil and primary coil will be : A .1: 10 B. 10: ( c cdot 1: 1 ) D. 11: |
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| 429 | A condenser of ( 250 mu F ) is connected in parallel to a cell of inductance ( 0.16 mathrm{mH} ) while its effective resistance is while its. Determine the resonant frequency. A ( cdot 9 times 10^{4} mathrm{Hz} ) B . ( 16 times 10^{7} ) Н ( _{2} ) c. ( 8 times 10^{5} ) Н ( z ) ( mathbf{D} cdot 9 times 10^{3} mathrm{Hz} ) |
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| 430 | A series LCR circuit is connected to an ac source. Using the phasor diagram, derive the expression for the impedance of the circuit. Plot a graph to show the variation of current with frequency of the source, explaining the nature of its variation. |
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| 431 | An ideal coil of 10 H is connected in series with a resistance of 5 12 and a battery of 5 V. Two seconds after the connection is made, the current flowing (in A) in the circuit is (a) e (b) e- (d) 1 -e (AIEEE 2007) To coaxial solenoids are mada ha (C) 1– |
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| 432 | In the given circuit (fig), all the symbols have their usual meanings. At ( t=0, ) key Kis closed. Now answer the following questions. At ( t rightarrow infty, ) the equivalent resistance between ( A ) and ( B ) is : ( mathbf{A} cdot R_{1}+R_{2}+R_{3} ) B. ( R_{1}+R_{2} ) ( mathbf{c} cdot R_{1}+R_{3} ) D. None of the above |
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| 433 | A coil has an inductance of ( 0.7 mathrm{H} ) and is joined in series with a resistance of 220 Omega. When an alternating e.m.f. of ( 220 mathrm{V} ) at 50 c.p.s. is applied to it, then the wattless component of the current in the circuit is A. 5 ampere B. 0.5 ampere c. 0.7 ampere D. 7 ampere |
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| 434 | In an A.C. circuit, the current flowing in inductance is ( boldsymbol{I}=mathbf{5} sin (mathbf{1 0 0} boldsymbol{t}-boldsymbol{pi} / mathbf{2}) ) ampers and the potential difference is ( =200 sin (100 mathrm{t}) ) volts. The power consumption is equal to A. 1000 watt B. 40 watt c. 20 watt D. zero |
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| 435 | Assertion An inductor coil normally produces more current with ( D C ) source compared to an ( A C ) source of same value of rms voltage. Reason In ( D C ) source applied voltage remains constant with time. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion C. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 436 | ( A 5 mu F ) capacitor is connected to a 200 ( mathrm{V}, 100 mathrm{Hz} ) ac source. The capacitive reactance is: ( mathbf{A} cdot 212 Omega ) B. ( 312 Omega ) c. ( 318 Omega ) D. ( 412 Omega ) |
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| 437 | In a series LCR circuit, what is the phase difference between ( V_{L} ) and ( V_{C} ) where ( V_{L} ) is the potential difference across the inductor and ( V_{C} ) is the potential difference across the capacitor? |
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| 438 | A transformer has 100 turns in the primary coil and carries 8 A current. If input power is ( 1 mathrm{kW} ), the number of turns in secondary coil to have ( 500 vee ) output will be: A ( cdot 100 ) B. 200 ( c cdot 400 ) D. 300 |
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| 439 | In the series LCR circuit shown the impedance is: A. ( 200 Omega ) B. ( 100 Omega ) c. ( 300 Omega ) D. ( 500 Omega ) |
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| 440 | Transformer works on ( 220 V . ) Its efficiency is ( 80 % ). Output power is ( 8 K W . ) Primary current is approximately. ( mathbf{A} cdot 35 A ) в. ( 18 A ) ( c .22 A ) D. ( 45 A ) |
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| 441 | An A.C. circuit containing only capacitance, the current: A . Lags the voltage by ( 90^{circ} ) B . Leads the voltage by ( 90^{circ} ) c. Remains in phase with voltage D. Lags the voltage by ( 180^{circ} ) |
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| 442 | An inductor ( 200 mathrm{mH} ), capacitor ( 500 mu mathrm{F} ) and resistor ( 10 Omega ) are connected in series with a ( 100 mathrm{V} ) variable frequency ac source. What is the frequency at which the power factor of the circuit is unity? A . ( 10.22 mathrm{Hz} ) B. 12.4 нz c. ( 19.2 mathrm{Hz} ) D. 15.9 нz |
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| 443 | What is meant by resonance in an LCR circuit? | 12 |
| 444 | A wire carrying ( 5.0 ~ V ) is applied to a transformer. The primary coil has 5 turns and the secondary coil has 10 turns. A . ( 0.50 V ) B. ( 5.0 V ) c. ( 10 V ) D. ( 50 V ) E . ( 100 V ) |
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| 445 | ( ln operatorname{an} mathrm{L}-mathrm{C} ) circuit ( boldsymbol{L}=mathbf{0 . 7 5} boldsymbol{H} ) and ( boldsymbol{C}= ) ( 18 mu F . ) At the instant when the current in the inductor is changing at a rate of ( 3.40 A / s, ) what is the charge on the capacitor? A ( .45 .9 mu C ) B. ( 15.9 mu C C ) ( c .55 .9 mu C ) D. ( 35.9 mu C ) |
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| 446 | In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit? A. Only resistor B. Resistor and inductor c. Resistor and capacitor D. Only inductor. |
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| 447 | A ( 100 Omega ) resistor is connected to a ( 220 V, 50 H z A C ) supply. Find net power consumed over a full cycle: ( mathbf{A} cdot 121 W ) B . ( 242 W ) c. ( 368 W ) D. ( 484 W ) |
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| 448 | A small signal voltage ( V(t)=V_{0} sin omega t ) is applied across an ideal capacitor ( boldsymbol{C} ) Then: A . current ( I(t) ), lags voltage ( V(t) ) by ( 90^{circ} ) B. over a full cycle the capacitor ( C ) does not consume any energy from the voltage source c. current ( I(t) ) is in phase with voltage ( V(t) ) D. current ( I(t) ) leads voltage ( V(t) ) by ( 180^{circ} ) |
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| 449 | Answer the following: What is the value of impedance of a resonant series LCR circuit? |
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| 450 | In an LCR circuit the capacitance is made ( frac{1}{4} ) then what should be the change in inductance that the circuit remains in resonance again? ( A cdot 8 ) times B. ( frac{1}{4} ) times ( c cdot 2 ) times D. 4 times |
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| 451 | If the resistance in a parallel resonant circuit is reduced, the bandwidth: A. increases B. decreases c. disappears D. become sharper |
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| 452 | Inductance ( L, ) capacitor ( C ) and resistor ( R ) are joined in series with an alternating voltage source ( V=v_{0} sin omega t ) Find the formula of impedance and phase angle, drawing vector diagram of the circuit. |
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| 453 | The ( Q ) factor of an ac circuit lies between: A. 0 and 1 B. – 1 and 1 c. -1 and 0 D. none of these |
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| 454 | 15. An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to (a) 80 H (b) 0.08 H (c) 0.044 H (d) 0.065 H (JEE Main 2016) |
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| 455 | In a series LCR circuit ( mathrm{R}=4 Omega, mathrm{XL}=5 Omega ) and ( X_{C}=8 Omega, ) the current A. leads the voltage by ( tan ^{-1}(3 / 4) ) B. leads the voltage by tan ( ^{-1}(5 / 8) ) C . leads the voltage by tan ( ^{-1}(3 / 5) ) D. leads the voltage by ( tan ^{-1}(5 / 9) ) |
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| 456 | An inductor may store energy in: A. its electric field B. its coils C . its magnetic field D. both in electric and magnetic fields |
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| 457 | What is the range between ( f_{1} ) and ( f_{2} ) of an RLC circuit that resonates at ( 150 k H z ) and has a ( Q ) of ( 30 ? ) A . ( 100.0 k H z ) to ( 155.0 k H z ) B. ( 147.5 k H z ) to ( 152.5 k H z ) c. ( 4500 k H z ) to ( 295.5 k H z ) D. ( 149970 H z ) to ( 150030 H z ) |
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| 458 | A transistor-oscillator using a resonant circuit with an inductor ( L ) (of negligible resistance) and a capacitor ( mathrm{C} ) in series produce oscillations of frequency f. If is doubled and ( C ) is changed to ( 4 C ), the frequency will be:- ( A cdot frac{f}{4} ) B. 8f ( c cdot frac{f}{2 sqrt{2}} ) ( D cdot frac{f}{2} ) |
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| 459 | 14. For the series LCR circuit shown in the figure, what is the resonance frequency and the amplitude of the current the resonating frequency 8 mH mm 20 F 220 v © 442 (a) 2500 rad- sand 572 A (b) 2500 rad-s- and 5 A (C) 2500 rad-s’ and A (d) 25 rad-s– and 572 A |
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| 460 | 11. A sinusoidal alternating current of peak value 10 passes through a heater of resistance R. What is the mean power output of the heater? (a) IOR (6) LOR (c) 21R (d) 21R |
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| 461 | Calculate inductive reactance of coil in the following figure. |
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| 462 | In a series resonant circuit, having L,C,R as its elements, the resonant current is i. The power dissipated in the circuit at resonance is ( mathbf{A} cdot i^{2} l omega ) B . ( i^{2} R ) c. zero ( mathbf{D} cdot i^{2} C omega ) |
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| 463 | If ( mathrm{N} ) is the number of turns in a coil, the value of self inductance varies as A . ( N^{0} ) B. c. ( N^{2} ) D. ( N^{-2} ) |
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| 464 | What is the average value of the AC voltage over one complete cycle? A. zero в. ( V_{max } ) c. ( frac{2 V_{max }}{pi} ) D. ( frac{V_{text {max }}}{2} ) |
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| 465 | e In the given circuit (figure), current through the 5 mH inductor in steady state is 5 mH M نادرا مهدی m 10 mH 20 V 522 win را نیا |
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| 466 | ( = ) ( frac{1}{4} ) ( = ) |
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| 467 | CARLOS 41. 34. The value of current in two series LCR circuits at resonance is same. Then (a) both circuits must be having same value of capacitance and inductance (b) in both circuits ratio of L and C will be same (c) for both the circuits X[/Xc must be same at that fre- quency (d) both circuits must have same impedance at all frequencies |
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| 468 | A resistor of ( 100 Omega ), a pure inductance coil of ( L=0.5 mathrm{H} ) and capacitor are in series in a circuit containing an a.c sources of ( 200 mathrm{V}, 50 mathrm{Hz} ). In the circuit, current is added is ahead of the voltage by ( 30^{0} . ) Find the value of the capacitance A . 1.46 B. 3 ( c cdot 4 ) D. 5 |
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| 469 | An ( L-C-R ) series circuit with ( L= ) ( 0.120 H, R=240 Omega, ) and ( C=7.30 mu F ) carries an rms current of ( 0.450 A ) with a frequency of ( 400 H z . ) The average rate at which electrical energy is converted to thermal energy in the resistor is given as ( frac{x}{10} W . ) Find ( x ) |
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| 470 | In series ( L-R ) circuit, ( X_{L}=R ). Now a capacitor with ( X_{C}=R ) added in series. New power factor: A. Same as initial B. ( frac{1}{sqrt{2}} ) times the initial c. ( frac{1}{2} ) times the initial D. ( sqrt{2} ) times the initial |
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| 471 | The number of turns in the primary and secondary of a transformer are, respectively 100 and ( 50 . ) If the input power and input current are, respectively ( 60 mathrm{W} ) and ( 1 mathrm{A} ), and the efficiency of the transformer is ( 0.95, ) then, the output power and the output current will be, respectively ( A cdot 60 mathrm{W}, 2 mathrm{A} ) B. ( 60 mathrm{W}, 1 mathrm{A} ) c. ( 57 mathrm{w} ), 2 ( mathrm{A} ) D. 57 W, 1.9 A |
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| 472 | 24. An inductor and a resistor are connected in series with an ac source. In this circuit. (a) the current and the PD across the resistance lead the PD across the inductance (b) the current and the PD across the resistance lag behind the PD across the inductance by an angle 7/2 (c) the current and the PD across the resistance lag behind the PD across the inductance by an angle it (d) the PD across the resistance lags behind the PD across the inductance by an angle rc/2 but the current in resistance leads the PD across the inductance by 7/2 |
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| 473 | An L-C-R circuit contains ( boldsymbol{R}=mathbf{5 0 Omega} ) ( boldsymbol{L}=mathbf{1} boldsymbol{m} boldsymbol{H} ) and ( boldsymbol{C}=mathbf{0 . 1} boldsymbol{mu} boldsymbol{F} . ) The impedence of the circuit will be minimum for a frequency of ( ^{mathbf{A}} cdot frac{10^{5}}{2 pi} H z ) в. ( frac{10^{6}}{2 pi} H z ) c. ( 2 pi times 10^{5} H z ) D. ( 2 pi times 10^{6} H z ) |
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| 474 | A step up transformer is connected on the primary side to a rechargeable battery which can deliver a large current. If a bulb is connected in the secondary, then A. the bulb will glow very bright B. the bulb will get fused c. the bulb will glow, but with less brightness D. the bulb will not glow |
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| 475 | If ( V=100 sin 100 t ) volt, and ( I= ) ( 100 sin left(100 t+frac{pi}{6}right) A . ) then find the watt less power in watt? A ( cdot 10^{text {। }} cdot 100 ) в. ( 10^{3} ) ( c cdot 10^{2} ) D. ( 2.5 times 10^{3} sqrt{3} ) |
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| 476 | The values of ( L, C ) and ( R ) in an ( L-C- ) ( R ) series circuit are ( 4 m H, 40 p F ) and 100 ( Omega ) respectively. The quality factor of the current is A . 10 B. 100 ( c cdot 1000 ) D. 10,000 |
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| 477 | ( ln ) an A.C circuit, the resistance ( boldsymbol{R}= ) ( 0.2 Omega . ) At a certain instant, ( V_{A}-V_{B}= ) ( 0.5 V, I=0.5 A, ) and the current is increasing at the rate of ( frac{Delta I}{Delta t}=8 A / s ) The inductance of the coil is: A . ( 0.05 H ) в. ( 0.1 mathrm{H} ) ( c .0 .2 H ) D. none of these |
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| 478 | A source of ( 220 mathrm{V} ) is applied in an ( mathrm{A} . mathrm{C} ) circuit. The value of resistance is ( 220 Omega ) Frequency ( & ) inductance are ( 50 mathrm{Hz} ) and 0.7 H, then wattless current is A . ( 0.5 a m p ) в. ( 0.7 a m p ) c. ( 1.0 a m p ) ( D cdot ) none |
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| 479 | 6. A group of electric lamps having a total power rating of 1000 watt is supplied by an ac voltage E = 200 sin(310t + 60°). Then the rms value o the circuit current is (a) 10 A (b) 10/2 A (c) 20 A (d) 2012 A |
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| 480 | To measure This question has multiple correct options A. you will measure the potential drop across resistor till it is minimum on varying frequency B. you will measure the voltage across ( L ) and ( C ) at various frequencies until ( V_{L}=V_{D} ) C. you will measure the voltage across L and C at various frequencies until ( V_{L}=V_{C} ) D. you will measure voltage across L until is minimum at a particular frequency |
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| 481 | Ratio of impedance to capacitive reactance has A . no units B. ohm c. ampere D. tesla |
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| 482 | In a primary coil ( 5 A ) current is flowing on 220 volts. If the secondary coil produces ( 2200 V ) voltage. Then the ratio of number of turns in secondary coil and primary coil will be ( mathbf{A} cdot 1: 10 ) B. 10: 1 c. 1: 1 D. 11: 1 |
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| 483 | ( ln operatorname{an} L-C-R ) circuit the capacitance is changed from ( C ) to ( 4 C ) For the same resonant frequency, the inductance should be changed from ( boldsymbol{L} ) to A . L/4 B. L/2 c. 2L D. 4L |
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| 484 | The phase difference between alternating emf and current in a purely capacitive circuit will be A . zero в. ( pi ) ( c cdot-frac{pi}{2} ) D. |
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| 485 | The circuit shown in Fig. acts as a A. tuned filter B. low pass filter c. high pass filter D. rectifier |
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| 486 | The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux ( phi ) linked with the primary coil is given by ( phi=phi_{0}+4 t, ) where ( phi ) is in weber, t is time in seconds and ( phi_{0} ) is a constant. The output voltage across the secondary coil is A ( .90 V ) ( V ) в. ( 6000 V ) c. ( 220 V ) D. 30 ( V ) |
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| 487 | An ( L-C ) circuit consists of a ( 20.0 m H ) inductor and a ( 0.5 mu F ) capacitor. If the maximum instantaneous current is ( 0.1 A, ) what is the greatest potential difference (in volts) across the capacitor? |
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| 488 | A step-down transformer increases the input current ( 4 A ) to 24 A at the secondary. If the, number of turns in the primary coil is ( 330, ) the number of turns in the secondary coil is A . 60 B. 50 ( c cdot 65 ) D. 45 E. 55 |
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| 489 | Alternating voltage ( V=400 sin (500 Omega t) ) is applied across the resistance ( (0.2 K Omega) . ) The r.m.s value of current in ampere is ( A cdot 1.414 mathrm{A} ) B. 14.14 A ( c cdot 0.1414 mathrm{A} ) ( D cdot 2 A ) |
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| 490 | Assertion In series ( L C R ) circuit if a ferromagnetic rod is inserted inside an inductor, current in the circuit may be increase or decrease Reason By doing so ( X_{L} ) will increase. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 491 | In the series LCR circuit (figure), the voltmeter and ammeter readings are: A. ( V=100 V, I=2 A ) B. ( V=100 V, I=5 A ) ( mathbf{c} . V=1000 V, I=2 A ) D. ( V=300 V, I=1 A ) |
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| 492 | Assertion At some given instant ( I_{1} ) and ( I_{2} ) both are ( mathbf{2} boldsymbol{A} ) each. Then ( boldsymbol{I} ) at this instant should be zero. Reason There is a phase difference of ( pi ) between ( I_{1} ) and ( I_{2} ) functions A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 493 | In a circuit, the current lags behind the voltage by a phase difference of ( pi / 2 ) the circuit will contain which of the following: A . Only R B. Only c c. ( R ) and ( c ) D. only L |
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| 494 | A coil has resistance ( 30 Omega ) and inductive reactance ( 20 Omega ) at ( 50 H z ) frequency.If an ac source of ( 200 V, 100 H z ) is connected across the coil, the current in the coil in the coil will be A ( cdot frac{20}{sqrt{13}} A ) в. ( 2.0 A ) c. ( 4.0 A ) D. ( 8.0 A ) |
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| 495 | A transformer connected to 220 volt line shows an output of ( 2 A ) at ( 11000 V . ) The efficiency is ( 100 % ). The current drawn from the line is: ( mathbf{A} cdot 100 A ) в. ( 200 A ) ( c .22 A ) D. ( 11 A ) |
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| 496 | The value of admittance at resonance in antiresonant A ( cdot sqrt{G^{2}-S^{2}} ) B . ( G^{2}+S^{2} ) c. ( sqrt{G^{2}+S^{2}} ) D. ( frac{G^{2}}{S^{2}} ) |
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| 497 | A transformer lowers emf from ( 220 V ) to ( 12 V ) If the number of turns in primary coil is 8800 , how many turns are there in the secondary coil? A . 200 B. 300 ( c cdot 480 ) D. 500 |
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| 498 | A current of 5 A is flowing at 220 V in the primary coil of a transformer. if the voltage produced in the secondary coil is ( 2200 mathrm{V} ) anf ( 50 % ) of power is lost, then the current in secondary will be |
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| 499 | While comparing the L-C oscillations with the oscillations of spring block system, with whom the magnetic energy can be compared and why? | 12 |
| 500 | The self inductance of a choke coil is mH. when it is connected with a 10 VDC source then the loss of power is 20 watt. When it connected with 10 volt ( A C ) source loss of power is 10 watt. The frequency of AC source will bw- ( A cdot 50 mathrm{Hz} ) B. 60 Н c. 80 н D. 100 нz |
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| 501 | The current in resistance ( mathrm{R} ) at resonance in ac circuit is A . zero B. minimum but finite c. maximum but finite D. infinite |
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| 502 | The reading of voltmeter and ammeter in the following figure will respectively be : ( A cdot O ) and ( 2 A ) B. 2A and OV c. ( 2 v ) and ( 2 A ) D. ov and on |
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| 503 | A resistance of ( 20 Omega ) is connected to a source of alternating current rated ( 110 V, 50 H z ) Find the ( r m s ) current |
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| 504 | The ( p . d . V ) across and current ( I ) flowing through an instrument in an ( a . c . ) circuit are given by ( V=2 cos omega t V ) and ( I= ) ( 2 sin omega t A . ) The power dissipated in the instrument is: ( mathbf{A} cdot 0 W ) B . ( 2.5 W ) c. ( 1.5 W ) D. ( 9 ~ W ) |
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| 505 | In the following circuit, the potential of source is ( boldsymbol{E}_{mathbf{0}}=mathbf{2 0 0} ) volts, ( boldsymbol{R}=mathbf{2 0 0 Omega} ) ( boldsymbol{L}=mathbf{0 . 1} ) henry, ( boldsymbol{C}=mathbf{1 0 . 6} ) farad and frequency is variable, then the current at ( f=0 ) and ( f=infty ) is : A. ( 0 A, 10 A ) B. 10A, OA C. ( 10 A, ) 10A D. OA, OA |
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| 506 | The phase angle between current and voltage in a purely inductive circuit is : A . zero в. ( pi ) ( c cdot pi / 4 ) D. ( pi / 2 ) |
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| 507 | A step down transformer changes the high input voltage used in our houses ( (120 V) ) into the low voltage used to charge an electric razor ( (24 V) . ) What must be the ratio of the turns of wire from the primary side of the transformer to the secondary side? A . 1: 5 в. 2: 7 ( c cdot 1: 8 ) D. 2: 9 E .1: 10 |
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| 508 | A transformer consists of a coil of 1200 turns and another coil, with a total of 120 turns, which can be tapped at various places. Primary voltage is ( 240 V . ) At which pair of terminals would you connect to a ( 12 V, 24 W ) lamp for it to be lit normally? A. ( N_{s}=60 ) is ( N_{s}=60 ) В. ( N_{s}=40 ) ( mathbf{C} cdot N_{s}=80 ) D. ( N_{s}=50 ) |
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| 509 | An AC source of angular frequency ( omega ) is fed across a resistor ( r ) and a capacitor ( C ) in series. The current registered is ( I ) If now the frequency of source is changed to ( omega / 3 ) (but maintaining the same voltage), the current in the circuit is found to be halved. Calculate the ratio of reactance to resistance at the original frequency ( omega ) A ( cdot sqrt{frac{3}{5}} ) B. ( sqrt{frac{2}{5}} ) c. ( sqrt{frac{1}{5}} ) D. ( sqrt{frac{4}{5}} ) |
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| 510 | Two different coils have self inductance ( boldsymbol{L}_{1}=mathbf{8} boldsymbol{m} boldsymbol{H} ) and ( boldsymbol{L}_{2}=boldsymbol{2 m} boldsymbol{H} . ) The currents in both are increasing at the same constant rate. At a certain instant of time, the power given to the two coils is the same. At this moment the current, the induced voltage and energy stored in the first coil are ( i_{1}, V_{1} ) and ( U_{1} ) respectively. The corresponding values in the second coil are ( i_{2}, V_{2} ) and ( U_{2} ) respectively. Then the values of ( frac{i_{1}}{i_{2}}, frac{V_{1}}{V_{2}} ) and ( frac{boldsymbol{U}_{1}}{boldsymbol{U}_{2}} ) are respectively: A ( cdot frac{1}{4}, 4, frac{1}{4} ) в. ( 4, frac{1}{4}, frac{1}{4} ) c. ( frac{1}{4}, frac{1}{4}, 4 ) D. ( _{4,4, frac{1}{4}} ) |
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| 511 | An RLC circuit has ( f_{1} ) and ( f_{2} ) as the half power frequency and ( f_{0} ) as the resonant frequency. The Q factor of the circuit is given by: A ( cdot frac{f_{1}+f_{2}}{2 f_{0}} ) в. ( frac{f_{1}-f_{0}}{f_{2}-f_{0}} ) c. ( frac{f_{0}}{f_{1}-f_{2}} ) D. ( frac{f_{1}-f_{2}}{f_{0}} ) |
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| 512 | 58. In a black box of unknown elements (L or R or any other combination), an ac voltage E = E, sin (@t + ) is applied and current in the circuit was found to be I=1, sin [@t+0+ (Tc/4)]. Then the unknown elements in the box may be (a) only capacitor (b) inductor and resistor both (c) either capacitor, resistor, and inductor or only capacitor and resistor (d) only resistor |
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| 513 | When the turns ratio of a step-up transformer is 20 and the primary ac voltage is ( 12 V ), the secondary voltage is A . ( 12 V ) B. ( 120 V ) c. ( 240 V ) D. 2, 400V |
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| 514 | 79. In the circuit shown, sliding contact is moving with uniform velocity towards right. Its value at some instance is 12 12. The current in the circuit at 0000000 this instant of time will be (a) 0.5 A (b) more than 0.5 A (c) less than 0.5 A (d) may be less or more than 0.5 A depending on the value • of L |
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| 515 | At resonant frequency the current amplitude in series LCR circuit is: A. maximum B. minimum c. zero D. infinity |
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| 516 | A sinusoidal voltage ( V=200 sin 314 t ) is applied to a ( 10 Omega ) resistor. Find the peak voltage ( mathbf{A} cdot 200 V ) B. ( 400 mathrm{V} ) ( mathbf{c} .600 V ) D. ( 800 mathrm{V} ) |
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| 517 | What is the phase difference between AC e.m.f and current in the following? Pure resistor and pure inductor. |
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| 518 | Vol112 3. The voltage time (V-t) + V. graph for triangular wave having peak value. Vo is /4 as shown in figure. The – V. average value of voltage Vin time interval from t = 0 to Tis (a) o (6) (d) none of these |
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| 519 | According to the law of conservation of energy, any load impedance connected to the ideal transformer’s secondary winding results in conservation of A. reactive power B. real c. apparent D. All of the above |
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| 520 | In ( A C ) circuits choke is preferred to resistors because A. choke coil is cheap B. voltage increase c. energy is not wasted. D. current increases |
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| 521 | In a circuit inductance ( L ) and capacitance ( C ) are connected as shown in figure. ( A_{1} ) and ( A_{2} ) are ammeters When key ( K ) is pressed to complete the |
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| 522 | The power loss in an AC circuit can be minimized by. A. Decreasing resistance and increasing inductance B. Decreasing inductance and increasimg resistance c. Increasing both inductance and resistance D. Decreasing both inductance and resistance |
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| 523 | In an alternating circuit applied voltage is ( 220 V . ) If ( R=8 Omega, X_{L}=X_{C}=6 Omega ) then write the values of the following: (a) Root mean square value of voltage. (b) Impedance of circuit. |
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| 524 | In an a.c. circuit, the instantaneous e.m.f. and current are given by ( e=100 sin 30 t ) ( i=20 sin left(30 t-frac{pi}{4}right) ) In one cycle of a.c., the average power consumed by the circuit and the wattless current are, respectively: ( mathbf{A} cdot 50,10 ) B. ( frac{1000}{sqrt{2}}, 10 ) c. ( frac{50}{sqrt{2}}, 0 ) D. 50,0 |
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| 525 | An rms voltage of ( 110 mathrm{V} ) is applied across a series circuit having a resistance ( 11 Omega ) and an impedance ( 22 Omega . ) The power consumed is A ( .275 ~ W ) в. ( 366 mathrm{W} ) ( c .550 W ) D. ( 1100 W ) |
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| 526 | The ac generator in the Figure supplies ( 150 V_{(max )} ) at ( 50 mathrm{Hz} . ) With the switch open as shown in the diagram, the resulting current leads the generator emf by ( 60^{circ} . ) With the switch in position 1, the current lags the generator emf by ( 30^{circ} . ) When the switch is in position ( 2, ) the maximum current is ( 3 A ) Then, the value of R is: A. ( 50 / sqrt{3} Omega ) B. 83.3 ( Omega ) c. ( 133.3 Omega ) D. ( 50 Omega ) |
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| 527 | In the AC circuit shown, ( X_{L}=7 Omega, R= ) ( 4 Omega ) and ( X_{c}=4 Omega . ) The reading of the ideal voltmeter ( V_{2} ) is ( 8 sqrt{2} ). The reading of the ideal ammeter will be: A . ( 1 A ) в. ( 2 A ) c. ( sqrt{2} A ) D. ( frac{1}{sqrt{2}} ) |
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| 528 | resistance leaus wie D DTU33 uit llluuulance by 25. Figure shows a source of alter-nating voltage conne to a cap-acitor and a resistor. Which of the following phasor diagrams correctly describes the phase relationship between Ic, the current between the source and the capacitor, and Ir, the current in the resistor? Ic IR (c) CR (d) |
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| 529 | ( 200 V ) A.C is applied at the ends of an LCR circuit. The circuit consists of an inductive reactance ( boldsymbol{X}_{boldsymbol{L}}=mathbf{5 0 Omega} ) capacitive reactance ( X_{C}=50 Omega ) and ohmic resistance ( R=10 Omega ). Calculate the impedance of the circuit and also potential difference across ( L ) and ( R ) What will be the potential difference across L-C? |
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| 530 | ge in when and 11. A coil of inductance 300 mH and resistance 2 is connected to a source of voltage 2 V. The current reaches half of its steady state value in (a) 0.3 s (b) 0.15 s (c) 0.1 s (d) 0.05 s (AIEEE 2005) |
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| 531 | In an A.C circuit, a resistance R is connected in series with an inductance L. If the phase angle between voltage and current be ( 45^{0}, ) the value of inductive reactance will be A ( cdot frac{R}{4} ) в. ( frac{R}{2} ) c. ( R ) D. ( frac{R}{3} ) |
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| 532 | In a transformer, in which the losses may be neglected, the ratio of the primary voltage to secondary voltage is found to be ( 4: 1 . ) The ratio of the primary to secondary turns and the ratio of the primary current to secondary current are respectively in the ratio of : ( A cdot 4: 1 & 1: 4 ) B. ( 1: 4 & 4: 1 ) c. ( 4: 1 & 4: 1 ) D. ( 1: 4 & 1: 4 ) |
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| 533 | An emf of ( 15 V ) is applied in a circuit of inductance ( 5 H ) and resistance ( 10 Omega ) The ratio of currents flowing at ( t=infty ) and ( t=1 s ) will be A ( cdot 1-e^{-1} ) B ( cdot e^{-1} ) c. ( frac{e^{2}}{e^{2}-1} ) D. ( frac{e^{1 / 2}}{e^{1 / 2}-1} ) |
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| 534 | In series combination of ( boldsymbol{R}, boldsymbol{L}, boldsymbol{C} ) with an A.C source at resonanace, if ( boldsymbol{R}=mathbf{2 0} ) ohm, then impedence ( Z ) of the combination is A. 20 ohm B. zero c. 10 ohm D. 400 ohm |
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| 535 | If the frequency of an alternating e.m.f. is ( f ) in ( L-C-R ) circuit, then the value of impedance ( mathbf{Z} ) as log(frequency) increases: A. increases B. increases and then becomes equal to resistance, then it will start decreasing c. decreases and when it becomes minimum, equal to the resistance then it will start increasing D. go on decreasing |
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| 536 | (0) 100 45. A resistor and an inductor are connected to an ac supply of 120 V and 50 Hz. The current in the circuit is 3 A. If the power consumed in the circuit is 108 W, then the resistance in the circuit is (a) 122 (b) 40 12 (c) (52 x 28) 2 (d) 360 12 |
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| 537 | A step-down transformer has a coil ratio of 1.5 to ( 17 . ) The voltage applied at the primary side of the transformer is ( 136 V ) What is the output voltage of the transformer? A . ( 1.2 V ) в. ( 1.5 V ) c. ( 5.25 V ) D. ( 12 V ) E . ( 18.75 V ) |
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| 538 | The instantaneous emf and current equations of an RLC series circuit are ( e=200 sin left(omega t-frac{pi}{6}right) ) ( i=20 sin left(omega t+frac{pi}{6}right) ) The average power consumed per cycle is A. zero в. ( 2000 mathrm{W} ) c. ( 1000 W ) D. ( 500 W ) |
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| 539 | Voltage across each elements of a series LCR circuit are given by ( V_{L}= ) ( mathbf{6 0} boldsymbol{V}, boldsymbol{V}_{boldsymbol{C}}=mathbf{2 0} boldsymbol{V}, boldsymbol{V}_{boldsymbol{R}}=mathbf{3 0} boldsymbol{V} ) Find out source voltage A . ( 50 v ) B. 100v ( c cdot 150 v ) D. 200v |
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| 540 | Plot a graph showing variation of capacitive reactance with the change in the frequency of the ( A C ) source. | 12 |
| 541 | With increase in frequency of an ac supply, the impedance of an ( L-C-R ) series circuit A. remains constant B. increases C . decreases D. decrease at first becomes minimum and then increases. |
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| 542 | The reactance of inductance at ( 10^{4} H z ) is ( 10^{4} Omega . ) Its reactance at ( 2 times 10^{4} H z ) will be: A ( cdot 10^{4} Omega ) B ( cdot 2 times 10^{4} Omega ) ( mathbf{c} cdot 3 times 10^{4} Omega ) D. ( 4 times 10^{4} Omega ) |
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| 543 | For a series LCR circuit at resonance, the statement which is not true is A. Peak energy stored by a capacitor = peak energy stored by an inductor B. Average power = apparent power C. Wattless current is zero D. Power factor is one |
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| 544 | The maximum current in the inductor is: A ( cdot frac{3 V_{0}}{2} sqrt{frac{3 C}{L}} ) 3. ( V_{0} sqrt{frac{3 C}{L}} ) ( ^{c} cdot 2 V_{0} sqrt{frac{3 C}{L}} ) ( v_{0} sqrt{frac{C}{I}} ) |
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| 545 | The primary winding of a transformer has 100 turns and its secondary winding has 200turns. The primary is connected to an A.C supply of ( 120 mathrm{V} ) and the current flowing in it is 10 A. The voltage and the current in the secondary are A. ( 240 V, 5 A ) в. ( 240 V, 10 A ) c. ( 60 V, 20 A ) D. ( 120 V, 20 A ) |
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| 546 | In above circuit, what is the potential drop across ( Z Y ? ) A ( cdot 160 ) B. ( 80 sqrt{80} ) ( c cdot 80 v ) ( D ) |
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| 547 | In a circuit ( mathrm{L}, mathrm{C} ) and ( mathrm{R} ) are connected in series with an alternating voltage source of frequency v. The current leads the voltage by ( 45^{0} . ) The value of ( C ) is A ( cdot frac{1}{pi v(2 pi v L-R)} ) B . ( frac{1}{2 pi v(2 pi u L-R)} ) c. ( frac{1}{pi v(2 pi v L+R)} ) D. ( frac{1}{2 pi v(2 pi v L+R)} ) |
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| 548 | Which of the following graphs represents the correct variation of capacitive reactance ( boldsymbol{X}_{C} ) with frequency ( nu ? ) ( A ) B. c. D. |
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| 549 | An inductor L of inductance ( boldsymbol{X}_{boldsymbol{L}} ) is connected in series with a bulb ( mathrm{B} ) and an ac source. How would brightness of the bulb change when (i) number of turn in the inductor is reduced, (ii) an iron rod is inserted in the inductor and (iii) a capacitor of reactance ( boldsymbol{X}_{boldsymbol{C}}=boldsymbol{X}_{boldsymbol{L}} ) is inserted in series in the circuit. Justify your answer in each case. |
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| 550 | The inductor in a LC oscillation has a maximum potential difference of ( 16 mathrm{V} ) and maximum energy of ( 640 mu ) J. Find the value of capacitor in ( mu ) F in LC circuit. A. ( F=5 mu F ) В. ( F=6 mu F ) c. ( F=7 mu F ) D. ( F=8 mu F ) |
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| 551 | In the given circuit, the value of resistance effect of the coil Lis exactly equal to the resistance R. Bulbs B1 and B2 are exactly identical. Answer the following question. a) Which one of the two bulbs lights up earlier, when key k is closed and why? b) What will be the comparative brightness of the two bulbs after sometime if the key ( mathrm{K} ) is kept closed and why? |
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| 552 | Assertion Potential difference across, resistor, capacitor and inductor each is ( 10 V ) Then, voltage function and current functions should be in phase. Reason At this condition current in the circuit should be maximum. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
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| 553 | A transformers has an efficiency of ( 80 % ) .It is connected to a power output of kw and 100 V.If the secondary voltage is ( 240 mathrm{V} ),the secondary current is A ( .4 .6 mathrm{A} ) B. 40 A ( c cdot 4.3 mathrm{A} ) D. 13.3 A |
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| 554 | The value of resistance of the coil calculated by the student is : A . ( 3 Omega ) в. ( 4 Omega ) ( c .5 Omega ) D. 8Omega |
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| 555 | ( mathbf{A} mathbf{5 0} boldsymbol{W}, mathbf{1 0 0} boldsymbol{V} ) lamp is to be connected to an ( A C ) mains of ( 200 V, 50 H z . ) What capacitance is essential to be put in series with the lamp? A . 9.2 B. 8 c. 10 D. 12 |
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| 556 | 11. When an ac source of e.m.f.e= E, sin(100t) is connected across a circuit, the phase difference between the emf e and the current i in the circuit is observed to be /4, as shown in the diagram. If the circuit consists possibly only of RC or LC in series, find the relationship between the two elements i ore (a) R=1 k92,C = 10 uF (b) R= 1 k-2, C = 1 uF (c) R = 1 k 2, L = 10 uH (d) R= 1 k 2, L = 1H |
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| 557 | In an a.c. circuit, containing an inductance and a capacitor in series, the current is found to be maximum when the value of inductance is 0.5henry and of capacitance is 8F. The angular frequency of the input A.C. Voltage must be equal to A. 0.5 B. 0.10 ( c ) D. 0.3 |
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| 558 | When ( Q=200 mu C, ) what is the value of I? |
12 |
| 559 | A ( 12 Omega ) resistor and a ( 0.21 H ) inductor are connected in series to an a.c source operating at ( 20 ~ V, 50 ) cycle/second. The phase angle between current and source voltage is A . ( 30^{circ} ) В . ( 40^{circ} ) ( c cdot 80^{circ} ) D. ( 90^{circ} ) |
12 |
| 560 | A power transmission line feeds input at ( 2200 mathrm{V} ) to a step-down transformer with its primary windings having 3000 turns. find the number of turns in the secondary to get the power input at 220 ( mathbf{V} ) |
12 |
| 561 | An ac circuit consist of a series combination of circuit elements ( X ) and ( Y . ) The Current is ahead of the voltage in phanse by ( frac{pi}{4} . ) If element ( X ) is a pure resistor of ( 100 Omega ) (a) name the circuit element ( Y ) (b) calculate the rms value of current, if rms value of voltage is ( 141 V ) (c) what will happen if the ac source is replaced by a dc source? |
12 |
| 562 | Determine the power consumed in the circuit in ( mathbf{w} ) |
12 |
| 563 | An AC source is connected to a resistive circuit. Which of the following is true? A. Current leads ahead of voltage in phase B. Current lags behind voltage in phase c. current and voltage are in same phase D. Any of the above may be true depending upon the value of resistance |
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| 564 | When the values of inductance and capacitance in an ( L-C ) circuit are ( 0.5 H ) and ( 8 mu F ) respectively then current in the circuit is maximum. The angular frequency of alternating e.m.f. applied in the circuit will be A ( .5 times 10^{3} ) Radian/sec B. 50 Radian/sec c. ( 5 times 10^{2} ) Radian/sec D. 5 Radian/sec |
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| 565 | The reactance of a circuit is zero. It is possible that the circuit contains This question has multiple correct options A. an inductor and a capacitor B. an inductor but no capacitor c. a capacitor but no inductor D. neither an inductor nor a capacitor |
12 |
| 566 | The quality factor of an AC circuit is related to bandwidth as A. inversely proportional B. directly proportional c. directly proportional to log D. inversely proportional to log |
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| 567 | If the total charge stored in the LC circuit is ( Q_{0}, ) then for ( t geq 0 ) A ( cdot ) the charge on the capacitor is ( mathrm{Q}=mathrm{Q}_{0} cos left(frac{pi}{2}+frac{mathrm{t}}{sqrt{mathrm{LC}}}right) ) B. the charge on the capacitor is ( mathrm{Q}=mathrm{Q}_{0} cos left(frac{pi}{2}-frac{mathrm{t}}{sqrt{mathrm{LC}}}right) ) c. the charge on the capacitor is ( Q=-L C frac{d^{2} Q}{d t^{2}} ) D. the charge on the capacitor is ( mathrm{Q}=-frac{1 mathrm{d}^{2} mathrm{Q}}{sqrt{mathrm{LC}} mathrm{d}^{2}} ) |
12 |
| 568 | Figure shows a LCR circuit connected with a dc battery of emf ( varepsilon ) and internal resistance ( R ). Initially the capacitor was uncharged. After a long time: This question has multiple correct options A ( cdot ) current through the inductor is ( frac{varepsilon}{8 R} ) B. charge stored in the capacitor is ( C frac{^{2}}{4} ) C. charge stored in the capacitor is ( C frac{e}{2} ) D. potential difference across the terminals of battery is ( frac{varepsilon}{4} ) |
12 |
| 569 | In the series ( L C R ) circuit as shown in figure, the voltmeter and ammeter readings are: A. ( V=100 ) volt, ( I=2 ) amp B. ( V=100 ) volt, ( I=5 ) amp c. ( V=1000 ) volt, ( I=2 ) amp D. ( V=300 ) volt, ( I=1 ) amp |
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| 570 | C, respectively, are connected in series with an inductor of inductance ( L ) Initially the capacitors have charge such that ( V_{B}-V_{A}=4 V_{0} ) and ( V_{C}- ) ( V_{D}=V_{0} . ) Initial current in the circuit is zero. Find: a. the maximum current that will flow in the circuit. b. the potential difference across each capacitor at that instant. ( mathbf{A} cdot I_{0}=V_{0} sqrt{frac{3 C}{L}} ; mathbf{b} . V_{1}=3 V_{0}, V_{2}=3 V_{0} ) B ( cdot I_{0}=V_{0} sqrt{frac{6 C}{L}} ; ) b. ( V_{1}=3 V_{0}, V_{2}=3 V_{0} ) C ( cdot I_{0}=V_{0} sqrt{frac{3 C}{L}} ; ) b. ( V_{1}=1.5 V_{0}, V_{2}=3 V_{0} ) D ( cdot I_{0}=V_{0} sqrt{frac{6 C}{L}} ; ) b. ( V_{1}=1.5 V_{0}, V_{2}=3 V_{0} ) |
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| 571 | The correct relation between the impedance of secondary coil with that of primary coil is ( mathbf{A} cdot Z_{S}=Z_{P} ) в. ( Z_{S}=Z_{P} frac{N_{S}}{N_{P}} ) ( ^{mathrm{c}} Z_{S}=Z_{P}left(frac{N_{S}}{N_{P}}right)^{2} ) D. ( _{Z_{S}}=Z_{P}left(frac{N_{P}}{N_{S}}right)^{2} ) |
12 |
| 572 | The instantaneous voltage through a device of impedence ( 20 Omega ) is ( e= ) ( 80 sin 100 pi t . ) The effective value of the current is ( A .3 A ) в. ( 2.828 A ) c. ( 1.732 A ) D. ( 4 A ) |
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| 573 | Which of the following graphs represents the correct variation of inductive reactane ( X_{L} ) with frequency ( v ) 7 ( A ) в. c. D. |
12 |
| 574 | An electrical device draws 2 kW power from ac mains voltage ( 223 V(r m s) ) The current differs lags in phase by ( phi=tan ^{-1}left(-frac{3}{4}right) ) as compared to voltage. The resistance ( R ) in the circuit is: A . ( 15 Omega ) B. 20Omega c. ( 25 Omega ) D. 30Omega |
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| 575 | An inductor of ( 30 mathrm{mH} ) is connected to a ( 220 mathrm{V}, 100 mathrm{Hz} ) ac source. The inductive reactance is then A . ( 10.58 Omega ) в. ( 12.64 Omega ) c. ( 18.85 Omega ) D. 22.67Omega |
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| 576 | 46. A resistor and a capacitor are connected to an ac supply of 200 V, 50 Hz in series. The current in the circuit is 2 A. If the power consumed in the circuit is 100 W then the resistance in the circuit is (a) 100 12 (b) 252 (c) /125 x 75 2 (d) 400 22 |
12 |
| 577 | A condenser of capacity ( C ) is charged to a potential difference of ( V_{1} ). The planes of the condenser are then connected to an ideal inductor of inductance ( L ). The current through the inductor when the potential difference across the condenser reduces to ( V_{2} ) is ? A ( cdot frac{Cleft(V_{1}^{2}-V_{2}^{2}right)}{L} ) B. ( frac{Cleft(V_{1}^{2}+V_{2}^{2}right)}{L} ) ( left(frac{Cleft(V_{1}^{2}-V_{2}^{2}right)}{L}right)^{1 / 2} ) ( left(frac{Cleft(V_{1}-V_{2}right)^{2}}{L}right)^{1 / 2} ) |
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| 578 | A resistor and a capacitor are connected to an ac supply of ( 200 V, 50 H z ) in series. The current in the circuit is ( 2 A ). If the power consumed in the circuit is ( 100 W ) then the resistance in the circuit is ( mathbf{A} cdot 100 Omega ) в. 25 ( Omega ) c. ( sqrt{125 times 75} Omega ) D. ( 400 Omega ) |
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| 579 | When a coil is connected to a ( 100 mathrm{V} ) DC supply, the current is 2 A. When the same coil is connected to AC source ( E=100 sqrt{2} sin omega t, ) the current is ( 1 A ) Find the inductive reactance used in the circuit. |
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| 580 | The output power in step-up transformer used in practice is A. Greater than the input power B. Equal to the input power c. Less than the input power D. None of the above |
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| 581 | A leaky capacitor ( 10 Omega / 60^{circ} ) is connected in series with a ( 10 Omega ) resistance. Find the overall impedance. Fig. 26.42 A. ( 10 Omega ) B. ( 10 sqrt{2} ) ? ( mathrm{c} cdot 15 Omega ) D. ( 10 sqrt{3} Omega ) |
12 |
| 582 | The potential difference between the ends of a resistance ( mathrm{R} ) is ( V_{R}, ) between the ends of capacitor is ( V_{C}=2 V_{R} ) and between the ends of inductance is ( V_{L}= ) ( 3 V_{R} ) then the alternating potential of the source in terms of ( V_{R} ) will be: A ( cdot sqrt{2} V_{R} ) в. ( V_{R} ) c. ( frac{V_{R}}{sqrt{2}} ) D. ( 5 V_{R} ) |
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| 583 | An alternating e.m.f. of ( 200 mathrm{V} ) and 50 cycles is connected to a circuit of resistance ( 3.142 Omega ) and inductance 0.01H. The lag in time between the e.m.f. and the current is : A . ( 1.5 mathrm{ms} ) B. 2.5 ms c. 3.5ms D. 0.5 ms |
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| 584 | ( S_{1}: ) In an elastic collision initial and final K.E. of system will be same. ( S_{2}: ) In a pure ( L-C ) Circuit average energy stored in capacitor is zero. ( S_{3}: ln Y D S E ) coherent sources are formed by division of wave front method ( S_{4}: ) If a physical Quantity is quantized then it must be integral multiple of it’s lowest value. A . FFTF в. ( T T F T ) c. ( F T F T ) D. ( T F T F ) |
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| 585 | A step up transformer operates on a 230 volt line and supplies to a load of 2 amp. The ratio of primary to secondary windings is ( 1: 25 . ) Determine the primary current A. 12.5 amp B. 50 amp c. 8.8 amp D. 25 amp |
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| 586 | Current flowing in the circuit | 12 |
| 587 | A transformer with primary to secondary turns ratio of ( 1: 2, ) is connected to an alternator of voltage ( 200 mathrm{V} . ) A current of ( 4 mathrm{A} ) is flowing through the primary coil. Assuming that the transformer has no losses, the secondary voltage and current are respectively: ( A cdot 100 vee, 8 A ) B. ( 400 vee, 8 A ) c. ( 400 vee, 2 mathrm{A} ) D. ( 100 vee, 2 A ) |
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| 588 | If ( E_{p} ) and ( E_{s} ) are the input and output voltages of a transformer, then: (where ( n_{p} ) is the number of turns in primary and ( n_{s} ) is the number of turns in secondary A ( cdot frac{E_{s}}{E_{p}}=frac{n_{p}}{n_{s}} ) B . ( E_{s} E_{p}=n_{s} n_{p} ) c. ( E_{s} n_{p}=E_{p} n_{s} ) D. None of these |
12 |
| 589 | 53. In the circuit shown in the figure, if both the bulbs B, and B2 are L = 10 mH identical, (a) their brightness will be the same 220 V, 50 Hz (b) B, will be brighter than B (c) B, will be brighter than B2 (d) only B, will glow because the capacitor has infinite impedance |
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| 590 | A resistor ( R ) on inductance ( 0.2 H ) and a capacitor of capacitance ( C ) are connected in series. A sinusoidal voltage of ( r m s ) value ( 200 V ) is applied across the combination using a fixed frequency oscillator. If the rms value of current through the circuit is ( 2.828 A ) and the inductive and capacitive reactances are ( 3 R ) and ( 2 R ) respectively. Calculate (i) resistance of the resistance of the resistor (ii) frequency of ( A C ) (iii) capacitance of the capacitor. ( begin{array}{ll}text { A. } & (500 Omega, 119.3 H z, 13.3 mu F)end{array} ) B. ( quad(50 Omega, 119.3 H z, 13.3 mu F) ) C. ( quad(50 Omega, 1193 H z, 133 mu F) ) D. ( quad(50 Omega, 0.1193 H z, 133 mu F) ) |
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| 591 | The transformation ratio in the step-up transformer is A . B. Greater than one c. Less than one D. The ratio greater or less than one depends on the other factors |
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| 592 | In the given circuit what is the potentia drop across resistance? A. ( 40 v ) B. 80 ( c cdot 120 v ) D. zer |
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| 593 | To step ( 110 V ) ac down to ( 20 V ) ac, the turns ratio must be A . 5.5 B . 18 c. 0.18 D. 0.018 |
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| 594 | An electrical heater and a capacitor are joined in series across a ( 220 V, 50 H z ) ( A C ) supply. The potential difference across the heater is ( 90 V . ) The potential difference across the capacitor will be about ( mathbf{A} cdot 200 V ) B. ( 130 V ) ( mathrm{c} cdot 110 mathrm{V} ) D. ( 90 V ) |
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| 595 | An ideal transformer is used on 220 V line to deliver 2 A at 110 V. The current through the primary is : ( A cdot 10 A ) B. 5 A ( c cdot 1 A ) D. 0.1 A |
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| 596 | A step-up transformer of turns ratio 2 1 has ( 50 H z A C ) voltage applied to primary. The frequency of ( A C ) output voltage across secondary is A. zero B. ( 25 H z ) ( mathbf{c} .50 H z ) D. ( 100 H z ) |
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| 597 | Primary coil of a step-up transformer has number of turns than secondary coil. A. more B. less c. same D. cant say |
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| 598 | An alternating current of ( 1.5 m A ) and angular frequency 300 rad/sec flows through a ( 10 K Omega ) resistor and a ( 0.50 mu F ) capacitor in series. find the rms voltage across the capacitor and impedance of the circuit? A ( cdot 1.2 times 10^{4} Omega ; 10 V ) B . ( 10^{4} Omega ; 10^{4} V ) c. ( 1.0 times 1.0^{4} Omega ; 50 V ) D. ( 10 Omega ; 10 v ) |
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| 599 | If a circuit made up of a resistance ( 1 Omega ) and inductance ( 0.01 mathrm{H}, ) and alternating emf ( 200 mathrm{V} ) at ( 50 mathrm{H} ) is connected, then the phase difference between the current and the emf in the circuit is : |
12 |
| 600 | In an ideal transformer, the voltage is stepped down from 11KV to 220V. If the primary current be 20 A the current in the secondary should be A. 5 k ( A ) B. 1 kA c. ( 0.5 mathrm{kA} ) D. 0.1 kA |
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| 601 | A resistance ( (R=12 Omega), ) an inductor ( boldsymbol{L}=mathbf{2} boldsymbol{H}) ) and a capacitor ( (boldsymbol{C}=mathbf{5} boldsymbol{mu} boldsymbol{F}) ) are connected to an AC generator of frequency ( 50 H z . ) Which of the following statement is correct? A. At resonance, the circuit impedance is zero B. At resonance, the circuit impedance is ( 12 Omega ) c. At resonance, the frequency of the circuit is ( 1 / 2 pi ) D. The inductive reactance is less than the capacitive reactance |
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| 602 | The self inductance of a coil is ( 1 / 2 ) henry. At what frequency will its inductive reactance be ( 3140 Omega ) A ( .100 H z ) B. ( 10 H z ) c. ( 1000 H z ) D. ( 10000 H z ) |
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| 603 | A light bulb is rated at ( 100 W ) for a ( 220 V ) supply. Find the resistance of the bulb: A . ( 184 Omega ) B. ( 284 Omega ) c. ( 384 Omega ) D. ( 484 Omega ) |
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| 604 | The inductive reactance of a choke coil of ( 1 / 4 pi m H ) in an ( A C ) circuit of ( 50 H z ) will be A. 25 ohm B. 0.25 ohm c. 0.025 ohm D. 2.5 ohm |
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| 605 | 10. Two alternating voltage generators produce emfs of the same amplitude E, but with a phase difference of 73. The resultant emf is (a) Esin[ax + (7/3)] (b) E, sin[or+ (1/6) (c) V3 E, sin[et + (rt/6)] (d) V3 E, sin[or+ (1/2)] 11 |
12 |
| 606 | Derive an expression for impedence and current in the series ( L C R ) circuit using phasor diagram |
12 |
| 607 | What is meant by rms (effective) value of alternating current? |
12 |
| 608 | A transformer steps up an AC supply from ( 220 mathrm{V} ) to ( 2200 mathrm{V} ). If the secondary coil of the transformer has 2000 turns, the number of turns in its primary coil will be : A . 200 B. 100 ( c .50 ) D. 20 |
12 |
| 609 | In a series LCR circuit connected to an ac source of variable frequency and voltage ( boldsymbol{v}=boldsymbol{v}_{m} sin omega boldsymbol{t}, ) draw a plot showing the variation of current (I) with angular frequency ( ( omega ) ) for two different values of resistance ( boldsymbol{R}_{1} ) and ( boldsymbol{R}_{2}left(boldsymbol{R}_{1}>right. ) ( left.R_{2}right), ) Write the condition under which the phenomenon of resonance occurs. For which value of the resistance out of the two curves a sharper resonance is produced? Define ( Q ) -factor of the circuit and give its significance |
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| 610 | A transformer with a ( 110 V ) primary has a 15: 1 turns ratio. The load resistance, ( R_{L}, ) is ( 120 . ) What is the approximate voltage across the load? A . ( 7.3 V ) B. ( 73 V ) ( c .88 V ) D. ( 880 V ) |
12 |
| 611 | 20 E alllla (AIEEE 2007) 16. An inductor of inductance L = 400 mH and resistors of resistances R1 = 2 ohm and R = 2 2 are connected to a battery of emf 12 V as shown in the figure. The internal resistance of the battery is negligible. The switch S is closed at t = 0. The potential drop across L as a function of time is (a) be stv (b) 1 2 3 (c) 6(1 – e-t/0.2) V (d) 12e-51 V (AIEEE 2009) |
12 |
| 612 | A transformer has an efficiency of ( 80 % ) It works at ( 4 mathrm{kW} ) and ( 100 mathrm{V} ). If the secondary voltage is ( 240 mathrm{V} ), the current in primary coil is ( mathbf{A} cdot 0.4 mathrm{A} ) B. 4 A c. 10 А D. 40 A |
12 |
| 613 | 63. In the adjoining ac circuit the voltmeter whose reading will be zero at resonance is mw (a) Vi (c) V₃ (b) V2 (d) V4 |
12 |
| 614 | An alternating e.m.f. of ( boldsymbol{E}= ) ( 100 sin (100 pi t) ) is connected to a choke of negligible resistance and current oscillations of amplitude 1 A are produced. The inductance of the choke should be ( mathbf{A} cdot 100 H ) в. ( frac{1}{pi} H ) c. ( 1 H ) D. ( pi H ) |
12 |
| 615 | ( A 220 V, 50 H z A C ) generator is connected to an inductor and a ( 50 Omega ) resistance in series. The current in the circuit is ( 1.0 A . ) What is the Potential difference across inductor? A. ( 102.2 V ) в. ( 186.4 mathrm{V} ) c. ( 214 V ) D. ( 170 V ) |
12 |
| 616 | How can you improve the quality factor of a parallel resonance circuit. Obtain the resonant frequency and quality factor of a series L-C-R circuit with ( L=4 mathrm{H}, mathrm{C}=64 mu F ) and ( mathrm{R}= ) ( 20 Omega ) |
12 |
| 617 | (9) TOU (d) 60° 40. In an ac circuit, V and I are given by V= 100 sin (100 t) volts, I = 100 sin wa mA. The power dissipated in circuit is (a) 104 watt (b) 10 watt (c) 2.5 watt (d) 5 watt |
12 |
| 618 | ( ln ) a parallel ( L-C-R ) circuit as shown in figure if ( I_{R}, I_{L}, I_{C} ) and ( I ) represents the rms values of current flowing through resistor, inductor, capacitor and the source, then choose the appropriate correct answer ( mathbf{A} cdot I=I_{R}+I_{L}+I_{C} ) В . ( I=I_{R}+I_{L}-I_{C} ) c. ( I_{L} ) or ( I_{C} ) may be greater than ( I ) D. None of the above |
12 |
| 619 | The ( Q ) – factor of a resonant circuit is equal to ( ^{mathbf{A}} cdot frac{1}{L} sqrt{frac{R}{C}} ) в. ( frac{1}{R} sqrt{frac{L}{C}} ) c. ( frac{1}{R L} sqrt{C} ) D. ( frac{1}{C} sqrt{frac{R}{L}} ) |
12 |
| 620 | The current in the coil decreases from 10 Amp to 5 Amp in 0.1 second.. Calculate the co-efficient of self- inductance if induced e.m.f. is ( 5 mathrm{V} ) |
12 |
| 621 | A generator at a utility company produces ( 100 A ) of current at ( 4000 V ) The voltage is stepped up to ( 240000 V ) by a transformer before it is sent on a high voltage transmission line. The current in transmission line is A ( .3 .67 A ) в. ( 2.67 A ) c. ( 1.67 A ) D. ( 2.40 A ) |
12 |
| 622 | A ( 10 Omega ) resistance, ( 5 m H ) coil and ( 10 mu F ) capacitor are joined in series. When a suitable frequency alternating current source is joined to this combination, the circuit resonates. If the resistance is halved, the resonance frequency: ( A ). is halved B. is doubled c. remains unchanged D. is quadrupled |
12 |
| 623 | In a purely inductive circuit, the current: A. is in phase with the voltage B. is out of phase with the voltage C . leads the voltage by ( pi / 2 ) D. lags behind the voltage by ( pi / 2 ) |
12 |
| 624 | In the adjoining circuit, calculate the inductive reactance and the capacitive reactance. What should be the source frequency so that the two reactance become equal in magnitude? What would then be the impedance(in ohms) of the circuit? |
12 |
| 625 | The net resistance of the circuit at resonance is ( ^{A} cdot frac{mathrm{L}}{mathrm{CR}} ) в. ( R ) ( c cdot frac{mathrm{CR}^{3}}{mathrm{L}} ) D ( frac{mathrm{L}^{2}}{mathrm{C}^{2} mathrm{R}^{3}} ) |
12 |
| 626 | A transformer is used to light a ( 120 W ) ( 24 V ) lamp from ( 240 V ) a.c. mains. The current in the main cable is ( 0.6 A . ) The efficiency of the transformer is A . ( 48 % ) B. ( 63.8 % ) c. ( 83.3 % ) D. ( 90 % ) |
12 |
| 627 | CISL UTIV 68. For the given circuit as summing inductor and source to be ideal, the phase difference between currents I, and l.is m |
12 |
| 628 | A series ( L C R ) circuit has an inductance of ( 100 m H, ) a capacitor ( 0.1 mu F ) and a resistance of ( 200 Omega ). Find the impedance at resonance and the resonant frequency. |
12 |
| 629 | The turn ratio of a transformer is ( 2: 3 . ) If the current through primary is ( 3 A ), then current through load resistance is ( A cdot 1 A ) B. 4.5 A ( c cdot 2 A ) D. 1.5 A |
12 |
| 630 | Calculate the total reactance if two inductor of ( 10 mathrm{mH} ) and ( 50 mathrm{mH} ) are connected in series with ( 10 mathrm{kHz} ) AC. |
12 |
| 631 | n the transformer shown in figure, the load resistor is ( 50 Omega ). The turns ratio ( N_{1}: N_{2} ) is 10: 2 and the source voltage is ( 200 mathrm{V}(mathrm{r} . mathrm{m} . mathrm{s}) . ) If a voltmeter across the load measures ( 25 mathrm{V} ) (r.m.s.), then the source resistance ( R_{S} ) is (power loss is negligible) ( A cdot 450 Omega ) в. ( 750 Omega ) c. ( 2000 Omega ) D. 100Omega |
12 |
| 632 | In a series L.C.R circuit, the potential drop across ( L, C ) and ( R ) respectively are ( 40 V, 120 V ) and ( 60 V . ) Then the source voltage is ( mathbf{A} cdot 220 V ) B. ( 160 V ) ( mathbf{c} cdot 180 V ) D. ( 100 V ) |
12 |
| 633 | An ( L C ) circuit contains a 20 m ( H ) inductor and a ( 50 mu F ) capacitor with an initial charge of 10 mC.The resistance of the circuit is negligible. Let the instant circuit is closed be at ( t=0 ) What is the total energy stored initial? Is it conserved during the ( L C ) oscillations? A. ( 0.01 mathrm{J} ), yes B. ( 0.1 mathrm{J} ), yes c. 1 J, yes D. 2 J, yes |
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| 634 | The value of current in two series ( L C R ) circuits at resonance is same. Then A. both circuits must be having same value of capacitance and inductance B. in both circuits ratio of ( L ) and ( C ) will be same c. for both the circuits ( X_{L} / X_{C} ) must be same at that frequency D. both circuits must have same impedance at all frequencies |
12 |
| 635 | The natural frequency of the circuit shown in fig. is A ( frac{1}{sqrt{L C}} ) B. ( frac{1}{2 sqrt{L C}} ) c. ( frac{2}{sqrt{L C}} ) D. none of these |
12 |
| 636 | If the rms current through a ( 6.8 k Omega ) resistor is ( 8 m A ), the rms voltage drop across the resistor is ( mathbf{A} cdot 5.44 V ) в. ( 54.4 mathrm{V} ) c. ( 7.07 V ) D. 8V |
12 |
| 637 | A series LCR circuit contains inductance ( 5 m H, ) capacitance ( 2 mu F ) and resistance ( 10 Omega ). If a frequency A.C. source is varied, what is the frequency at which maximum power is dissipated? ( ^{mathbf{A}} cdot frac{10^{5}}{pi} H z ) в. ( frac{10^{-5}}{pi} H z ) c. ( frac{2}{pi} times 10^{5} H z ) D. ( frac{5}{pi} times 10^{3} H z ) |
12 |
| 638 | The amount of power delivered by the AC source in the capacitor ( & ) resistance ( R_{1} ) of the circuit given above is ( frac{X}{8} times 10^{3} ) watt. Then x is: |
12 |
| 639 | ( ln a R, L, C ) circuit, three elements is connected in series by an a.c. source. If frequency is less than resonating frequency then net impedance of the circuit will be A. capacitive B. inductive c. capacitive or inductive D. pure resistive |
12 |
| 640 | The input AC voltage to the transformer is ( 3 mathrm{kV} ) and output is ( 100 mathrm{V} ). Then: A. The ratio of number of turns in the primary to secondary coil is 30: 1 B. The transformer is a step down transformer c. The transformer is a step up transformert D. Both 1 and 2 |
12 |
| 641 | A series resonant circuit contains ( boldsymbol{L}= ) ( frac{5}{pi} m H, C=frac{200}{pi} mu F ) and ( R=100 mu ). If a source of emf ( e=200 sin 1000 pi t ) is applied, then the rms current is: A ( .2 A ) в. ( 200 sqrt{2} A ) D. ( 1.41 A ) |
12 |
| 642 | In an a.c., circuit with phase voltage ( boldsymbol{V} ) and current ( I ), the power dissipated is ( ^{A} cdot frac{V I}{2} ) B. ( frac{V I}{sqrt{2}} ) c. ( V I ) D. VIcostheta |
12 |
| 643 | The effective resistance in between the points A and B in the circuit given is? |
12 |
| 644 | The primary to secondary turns ratio of a transformer is given as ( 2: 3 . ) If the current through the primary coil is ( 3 A ) then the current through load resistance is ( A cdot 1 A ) в. 4.5 А ( c cdot 2 A ) D. 1.5 A |
12 |
| 645 | 22. In the series LCR circuit (see figure), the voltmeter and ammeter readings are: 400 V 400 V R = 50 S2 L 100 V, 50 Hz (a) V= 100 V, I = 2 A (c) V = 1000 V, I= 2 A (b) V= 100 V, 1 = 5 A (d) V= 300 V, I = 1 A |
12 |
| 646 | A resistor ( R, ) inductor ( L ) and a capacitor ( mathrm{C} ) are connected in series to an oscillator of frequency v. If the resonant frequency is ( boldsymbol{v}_{r}, ) then the current lags behind the voltage, when: ( mathbf{A} cdot v=0 ) В. ( vv_{r} ) D. ( v=v_{r} ) |
12 |
| 647 | A transformer consists of 500 turn in the primary coil and 10 turns in a secondary coil with the load of ( 10 Omega ) Find out current in the primary coil when the voltage across the secondary coil is ( mathbf{5 0} boldsymbol{V} ) A . ( 5 A ) в. ( 1 A ) ( c cdot 10 A ) D. ( 2 A ) |
12 |
| 648 | 17. A resistance of 20 2 is connected to a source of an alter- nating potential V = 220 sin(100 g). The time taken by the current to change from the peak value to rms value, is (a) 0.2 s (b) 0.25 s (c) 2.5 x 10-s (d) 2.5 x 10-s |
12 |
| 649 | A coil of ( 10^{-2} H ) inductance carries a current ( boldsymbol{I}=2 sin (mathbf{1 0 0} boldsymbol{t}) boldsymbol{A} . ) When current is half of its peak value then at that instant the induced emf in coil :- A . ( 1 V ) B. ( sqrt{2} V ) c. ( sqrt{3} V ) D. 2 |
12 |
| 650 | Potential difference across capacitor of capacitance ( C ) when the current in the circuit is maximum is: a. ( frac{V_{0}}{4} ) в. ( frac{3 V_{0}}{4} ) ( c cdot frac{5 V_{0}}{4} ) D. none of these |
12 |
| 651 | The figure shows the graphical variation of the reactance of a capacitor with frequency of ac source. Draw the graph showing the variation of |
12 |
| 652 | ( ln L-C ) oscillations This question has multiple correct options A ( cdot ) time period of oscillations is ( frac{2 pi}{sqrt{L C}} ) B. maximum current is ( frac{q_{0}}{sqrt{L C}} ) C. maximum rate of change of current in circuit is ( frac{q_{0}}{L C} ) D. maximum potential difference across the inductor is ( frac{q_{0}}{2 C} . ) Here ( q_{0} ) is maximum charge on capacitor. |
12 |
| 653 | A sinusoidal voltage of peak value ( 283 V ) and angular frequency ( 320 / s ) is applied to a series LCR circuit. Given that ( boldsymbol{R}=mathbf{5} boldsymbol{Omega}, boldsymbol{L}=mathbf{2 5} boldsymbol{m} boldsymbol{H} ) and ( boldsymbol{C}= ) 1000 ( mu F ). The total impedance, and phase difference between the voltage across the source and the current will respectively be: ( mathbf{A} cdot 7 Omega ) and ( 45^{circ} ) B. ( 10 Omega ) and ( tan ^{-1}left(frac{5}{3}right) ) c. ( 10 Omega ) and ( tan ^{-1}left(frac{8}{3}right) ) D. ( 7 Omega ) and ( tan ^{-1}left(frac{5}{3}right) ) |
12 |
| 654 | The resonance point in ( boldsymbol{X}_{L}-boldsymbol{f} ) and ( X_{c}-f ) curve is ( r ) |
12 |
| 655 | In an oscillating LC circuit the maximum charge on the capacitor is ( Q ) The charge on the capacitor when the energy is stored equally between the electric and magnetic field is: A ( cdot frac{Q}{3} ) в. ( frac{Q}{sqrt{3}} ) c. ( frac{Q}{sqrt{2}} ) D. |
12 |
| 656 | ( ln ) an ac circuit, the resistance of ( mathrm{R} Omega ) is connected in series with an inductance I. If phase angle between voltage and current be ( 45^{circ}, ) the value of inductive reactance will be: A. ( R / 2 ) B. ( R / sqrt{2} ) ( c . R ) D. Insufficient data |
12 |
| 657 | Define capacitor reactance. Write its S.I. units |
12 |
| 658 | An alternating voltage given as ( boldsymbol{V}= ) ( mathbf{1 0 0} sqrt{mathbf{2}} sin 100 t quad ) is applied to a capacitor of ( 1 mu F ). The current reading of the ammeter will be equal to ( mathrm{mA} ) A . 10 B . 20 c. 40 D. 80 |
12 |
| 659 | An alternating emf given by equation ( boldsymbol{E}=mathbf{3 0 0} sin [(mathbf{1 0 0} boldsymbol{pi}) boldsymbol{t}] ) volt is applied to a resistance 100 ohms. The rms current through the circuit is (in amperes): ( ^{A} cdot frac{3}{sqrt{2}} ) в. ( frac{9}{sqrt{2}} ) ( c cdot 3 ) D. ( frac{6}{sqrt{2}} ) |
12 |
| 660 | un connected in the circuit as shown in fig. Initially capacitor A has no charge and capacitor ( mathrm{B} ) has ( mathrm{CV} ) charge. Assume that the circuit has no resistance at all. At ( t=0, ) switch ( S ) is closed, then ( [ ) given ( boldsymbol{L} boldsymbol{C}=frac{boldsymbol{2}}{boldsymbol{pi}^{2} times mathbf{1 0}^{4}} boldsymbol{s}^{2} ) and ( boldsymbol{C V}=mathbf{1 0 0 m C} ) This question has multiple correct options A. when current in the circuit is maximum, charge on each capacitor is same B. when current in the circuit is maximum, charge on capacitor A is twice the charge on capacitor C ( . q=50(1+cos 100 pi t) m C, ) where ( q ) is the charge on capacitor B at time t D. ( q=50(1-cos 100 pi t) m C ), where q is the charge on capacitor B at time t |
12 |
| 661 | The primary winding of transformer has 500 turns whereas its secondary has ( mathbf{5 0 0 0} ) turns. The primary is connected to an A.C supply of ( 20 V, 50 H z ). The secondary will have an output of A. ( 2 V, 5 H z ) в. ( 200 V, 500 H z ) ( mathbf{c} cdot 2 V, 50 H z ) D. ( 200 V, 50 H z ) |
12 |
| 662 | In an A.C. circuit, the instantaneous values of e.m.f. and current are ( boldsymbol{E}= ) ( 200 sin 314 t ) volts and ( I=sin (314 t+ ) ( pi / 3) ) ampere then the average power consumed in watts is A . 200 B. 100 ( c cdot 0 ) D. 50 |
12 |
| 663 | If in an A.C., L-C series circuit ( boldsymbol{X}_{c}>boldsymbol{X}_{boldsymbol{L}} ) Hence potential A. Lags behind the current by ( pi / 2 ) B. Leads the current by ( pi ) in phase c. Leads the current by ( pi / 2 ) in phase D. Lags behind the current by ( pi ) in phase |
12 |
| 664 | & In the circuit shown in figure neglecting source resistance the voltmeter and ammeter reading will respectively, will be R=300X2= 252 X=259 240 V (a) OV, 3 A (c) 150 V, 6 A (b) 150 V, 3A (d) OV,8A |
12 |
| 665 | For an LCR circuit, the power transferred from the driving source to the driven oscillator is ( boldsymbol{P}=boldsymbol{I}^{2} boldsymbol{Z} ) cos ( boldsymbol{p} ) Then A. the power factor ( cos phi>0, P>0 ) B. the driving force can give no energy to the oscillator (P ( =0 ) ) in some cases. C. the driving force cannot syphon Out (P ( <0 ) ) the energy out of oscillator. D. all of these. |
12 |
| 666 | An inductor ( 200 m H, ) capacitor ( 500 mu F ) resistor ( 10 Omega ) are connected in series with a ( 100 V ), variable frequency ac source. Calculate: (i) frequency at which power factor of circuit its unity (ii) current amplitude at this frequency (iii) Q-factor. |
12 |
| 667 | If the current in a primary coil of transformer decreases from ( 0.8 mathrm{A} ) to 0.2 ( A ) in 4 millisecond, then calculate induced emf in the secondary coil [Coefficient of mutual induction is 1.76 ( mathrm{H}] ) |
12 |
| 668 | 33. For the circuit shown in the figure, the ammeter A, reads 1.6 A and ammeter Az reads 0.4 A. Then (a) 0= TIC (b) f= TIC (c) the ammeter A, reads 1.2 A (d) the ammeter A, reads 2 A |
12 |
| 669 | When the frequency of the voltage applied to a series RC circuit is increased, the phase angle A . increases B. decreases c. remains the same D. becomes erratic |
12 |
| 670 | Assertion A given transformer can be used to step-up or step-down the voltage Reason The output voltage depends upon the ratio of the number of turns of the two coils of the transformer A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion C. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
12 |
| 671 | A transformer steps up an ac supply from 220 to 2200 V. If the secondary coil of the transformer has 2000 turns, Then find the number of turns in its primary coil : ( mathbf{A} cdot N_{p}=250 ) turns B. ( N_{p}=300 ) turns C ( . N_{p}=100 ) turns D. ( N_{p}=200 ) turns |
12 |
| 672 | A current ( i_{0} ) is flowing through an ( L-R ) circuit of time constant ( t_{0} . ) The source of the current is switched off at time ( boldsymbol{t}=mathbf{0} . ) Let ( boldsymbol{r} ) be the value of ( (-boldsymbol{d i} / boldsymbol{d} boldsymbol{t}) ) at time ( t=0 . ) Assuming this rate to be constant, the current will reduce to zero in a time interval of: A ( cdot t_{0} ) B . ( e t_{0} ) ( c cdot t_{0} / e ) D. ( left(1-frac{1}{e}right) t_{0} ) |
12 |
| 673 | A ( 5 c m ) long solenoid having 10 ohm resistance and ( 5 m H ) inductance is joined to a ( 10 V ) battery. At steady state, the current through the solenoid (in ampere) will be ( mathbf{A} cdot mathbf{5} ) B . 2 ( c . ) D. zero |
12 |
| 674 | Assertion A capacitor blocks the direct current in the steady state. Reason The capacitive reactance of the capacitor is inversely proportional to frequency ( f ) of the source of emf. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
12 |
| 675 | In the circuit shown, a ( 30 mathrm{V} ) d.c source gives a current ( 2.0 mathrm{A} ) as recorded in the ammeter ( A ) and ( 30 V ) a.c. source of frequency ( 100 mathrm{Hz} ) gives a current ( 1.2 mathrm{A} ) The inductive reactance is ( A cdot ) 10ohm B. 20 ohm ( mathbf{c} cdot 5 sqrt{34} ) ohm D. 40 ohm |
12 |
| 676 | The sum of rms potential difference across each of the three elements is A . 50 volt B. ( 50 sqrt{2} ) volt c. ( frac{50}{sqrt{2}} ) volt D. None of these |
12 |
| 677 | A transformer has 200 turns in primary and 400 turns in secondary. When a battery of ( 6 mathrm{V} ) and negligible internal resistance is connected to the primary a current of ( 2 mathrm{A} ) is produced in it. The secondary voltage and current are ( A cdot 12 v, 1 A ) B. 12 V, zero c. zero, 1A D. zero, zero |
12 |
| 678 | An inductance, a capacitance and a resistance are connected in series across a source of alternating voltages. At resonance, the applied voltage and the current flowing through the circuit will have a phase difference of A . ( pi / 4 ) B. zero ( c ) D. ( pi / 2 ) |
12 |
| 679 | Assertion: In series LCR circuit resonance can take place. Reason: Resonance takes place if inductance and capacitive reactances are equal and opposite. A. If both assertion and reason are true but the reason is the correct explanation of assertion. B. If both assertion and reason are true but the reason is not the correct explanation of assertion c. If assertion is true but reason is false D. If both the assertion and reason are false E. If reason is true but assertion is false |
12 |
| 680 | Assertion ( ln operatorname{an} A C ) circuit potential difference across the inductor may be greater than the applied voltage. Reason ( boldsymbol{V}_{C}=boldsymbol{I} boldsymbol{X}_{C}, ) whereas ( boldsymbol{V}=boldsymbol{I} boldsymbol{Z} ) and ( boldsymbol{X}_{boldsymbol{C}} ) can be greater than ( Z ) also. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
12 |
| 681 | Quality factor of series resonance circuit is given by A ( cdot frac{f_{2}-f_{1}}{f_{0}} ) в. ( f_{2}-f_{1} ) c. ( frac{f_{1}-f_{0}}{f_{2}} ) D. ( frac{f_{0}}{f_{2}-f_{1}} ) |
12 |
| 682 | With increase in frequency of an AC supply, the impedence of an L-C-R series circuit A. remains constant B. increases c. decreases D. decreases at first, becomes minimum and then increases |
12 |
| 683 | Assertion The inductive reactance limits amplitude of the current in a purely inductive circuit Reason The inductive reactance is independent of the frequency of the current A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
12 |
| 684 | 59. In an ideal transformer, the voltage and the current in the primary coil are 200 V and 2 A, respectively. If the voltage in the secondary coil is 2000 V, then the value of current in the secondary coil will be (a) 0.2 A (b) 2 A (c) 10 A (d) 20 A |
12 |
| 685 | 2 39. What will be the phase difference between virtual voltage and virtual current, when the current in the circuit is wattless? (a) 90° (b) 45° (c) 180° (d) 60° |
12 |
| 686 | An alternating voltage of 260 volt and ( omega ) ( =100 ) radian/second, is applied in an LCR series circuit where ( mathrm{L}=0.01 mathrm{H}, mathrm{C}=4 times ) ( 10^{-4} F ) and ( R=10 Omega . ) the power supplied by the source is: A. 1000 w в. 6760 w ( c . ) 3380 ( w ) D. 3000 |
12 |
| 687 | What do you mean by electrical resonance? An LC circuit is in a condition of resonance. If ( C=1.0 times 10^{-6} ) ( F ) and ( L=0.25 H, ) then find the frequency of oscillation of the circuit. |
12 |
| 688 | An oscillator circuit contains an inductor ( 0.05 H ) and a capacitor of capacity ( 80 mu F ).When the maximum voltage across the capacitor is ( 200 V ) the maximum current (in amperes) in the circuit is ( A cdot 2 ) B. 4 c. 8 D. 10 E. 16 |
12 |
| 689 | The natural frequency of a ( L-C ) circuit is A ( cdot frac{1}{2 pi sqrt{L C}} ) в. ( frac{1}{2 pi} sqrt{frac{C}{L}} ) c. ( frac{1}{2 pi} sqrt{frac{L}{C}} ) D. ( sqrt{L C} ) |
12 |
| 690 | ( frac{-}{k} ) | 12 |
| 691 | The phase difference between alternating emf and current in a purely capacitive circuit will be A . zero в. ( pi ) ( c cdot-frac{pi}{2} ) D. |
12 |
| 692 | Which of the following combination should be selected for better turning of an L.C.R circuit used for communication? A. ( R=25 Omega, L=1 cdot 5 H, C=45 mu F ) в. ( R=25 Omega, L=1 cdot 5 H, C=35 mu F ) c. ( R=25 Omega, L=2 cdot 5 H, C=45 mu F ) |
12 |
| 693 | In ( P-f ) curve the half power frequencies are those at which A ( cdot P=frac{P_{max }}{sqrt{2}} ) B. ( P=frac{P_{text {max }}}{2} ) c. ( quad P=frac{P_{max }}{4} ) D. ( P=P_{max } ) |
12 |
| 694 | An alternating voltage ( boldsymbol{V}=boldsymbol{V}_{0} sin (boldsymbol{omega} boldsymbol{t}) ) is applied across a circuit. As a result, a current ( boldsymbol{I}=boldsymbol{I}_{0} sin (boldsymbol{omega} boldsymbol{t}-boldsymbol{pi} / 2) ) flows in it The power consumed per cycle is A . zero в. ( 0.5 V_{0} I_{0} ) c. ( 0.707 V_{0} I_{0} ) D. ( 1.414 mathrm{V}_{0} mathrm{I}_{0} ) |
12 |
| 695 | (U) Lei 62. The reading of ammeter in the circuit shown will be r. x c=50 0 110v X = 522 R= 552 (a) 2 A (2) 2 A (c) Zero (b) 2.4 A (d) 1.7 A |
12 |
| 696 | In a Zener regulated power supply a Zener diode with ( V_{z}=6.0 V ) is used for regulation. The load current is to be ( 4.0 m A ) and the unregulated input is ( 10.0 V . ) What should be the value of series resistor ( boldsymbol{R}_{s} ) |
12 |
| 697 | A lamp consumes only ( 50 % ) of maximum power applied in an AC circuit. What will be the phase difference between applied voltage and circuit current? A ( cdot frac{pi}{3} r a d ) B. ( frac{pi}{6} r a d ) c. ( frac{pi}{4} r a d ) D. ( frac{pi}{2} r a d ) |
12 |
| 698 | A step down transformer having efficiency of ( 75 % ) supplies 3 ampere current at 120 volt. Calculate the current in its primary coil, if it is operated at 440 volt. ( A cdot 2 ) B. ( c cdot 3 ) D. 4 |
12 |
| 699 | A step-down transformer converts transmission line voltage from ( 11000 V ) to ( 220 V ) The primary of the transformer has 6000 turns and the efficiency of the transformer is ( 60 % ). If the output power is ( 9 k W, ) then the input power will be ( mathbf{A} cdot 11 k W ) в. ( 12 k W ) c. ( 14 k W ) D. ( 15 k W ) |
12 |
| 700 | A step-up transformer works on ( 220 mathrm{V} ) and gives 2 A to an external resistor. The ratio of the number of turns between the primary and secondary coils is 2: 25 Assuming ( 100 % ) efficiency, find the secondary voltage, primary current and power delivered A . 2750 ( vee, ) 25 ( A, 5500 W ) B. 2750 V, 20 A, 5000 W c. 2570 V, 25 A, 550 D. 2750 V, 20 A, 55 W |
12 |
| 701 | toppr Q Type your question 3 ( c ) ( D ) |
12 |
| 702 | A power transmission line feeds input power at ( 2300 V ) to a step-down transformer, with its primary winding having 4000 turns. What should be the number of turns in the secondary winding in order to get output power at ( mathbf{2 3 0} boldsymbol{V} ? ) A . 300 в. 250 ( c .400 ) D. 450 |
12 |
| 703 | Leading is ( frac{x}{1000} H ) | 12 |
| 704 | If the frequency of an A.C is made 4 times of its initial value, the inductive reactance will ( A cdot ) be 4 times B. be 2 times c. be half D. remain the same |
12 |
| 705 | The instantaneous values of alternating current and voltages in a circuit are given as ( i=frac{1}{sqrt{2}} sin (100 pi t) ) ampere ( e=frac{1}{sqrt{2}} sin (100 pi t+pi / 3) ) volt The average power in Watts consumed in the circuit is – A. ( frac{sqrt{3}}{4} ) в. ( c cdot frac{1}{8} ) D. |
12 |
| 706 | The resistance ( R=10 Omega ), inductance ( L= ) ( 2 mathrm{mH} ) and capacitance ( operatorname{cof} 5 mu F ) are connected in same to an AC source of frequency ( 50 mathrm{Hz} ), then at resonance the impedance of circuit is A. zero B. ( 10 Omega ) c. ( 1000 Omega ) D. ( 10 k Omega ) |
12 |
| 707 | connected to a resistance ( R ) and two ideal inductors ( L_{1} ) and ( L_{2} ) through a switch ( S ) as shown. There is no mutual inductance between the two inductors. The switch ( S ) is initially open. At ( t=0 ) the switch is closed and current beings to flow. Which of the following options is/are correct? A. After a long time, the current through ( L_{1} ) will be ( frac{V L_{2}}{R L_{1}+L_{2}} ) B. After a long time, the current through ( L_{2} ) will be ( frac{V L_{2}}{R L_{1}+L_{2}} ) c. The ratio of the currents through ( L_{1} ) and ( L_{2} ) is fixed at all times ( (t>0) ) Det the current through the resistance ( R ) is ( frac{V}{R} ) |
12 |
| 708 | State whether given statement is True or False
The resistor voltage is always out of phase with the current. |
12 |
| 709 | 42. What is the amount of power delivered by the ac source in the circuit shown (in watts). Xc = 1222 R = 522 Xi = 8 12 R2 = 622 Ems = 130V (a) 500 watt (c) 1514 watt (b) 1014 watt (d) 2013 watt |
12 |
| 710 | The given graph shows variation with time in the source voltage and steady state current drawn by a series RLC circuit. Which of the following statements |
12 |
| 711 | A resistor of resistance ( 100 Omega ) is connected to an AC source ( varepsilon= ) ( (12 V) sin left(250 pi s^{-1}right) t . ) Find the energy dissipated as heat during ( t=0 ) to ( t= ) 1.0 ms. |
12 |
| 712 | The reactance of a ( 2.00 mu F ) capacitor at a frequency of ( 50.0 H z ) is ( frac{x}{10} k Omega . ) Find ( x ) | 12 |
| 713 | If the resistance is removed from the circuit and the value of induction is doubled, then the variation of current with time in the new circuit is given as ( frac{x}{100} cos 314 t . ) The value of ( x ) is |
12 |
| 714 | A transformer of efficiency ( 90 % ) has turns ratio ( 1: 10 . ) If the voltage across the primary is ( 220 V ) and current in the primary is ( 0.5 A ), then the current in secondary is ( mathbf{A} cdot 5.5 A ) B. ( 5 A ) ( c cdot 4 A ) D. ( 4.5 ~ A ) |
12 |
| 715 | The Sl unit of inductance, henry, can be written as: A. weber/ampere B. volt second/ampere c. joule/ampere ( ^{2} ) D. all of these |
12 |
| 716 | What do you mean by resonance in ( L C R ) series circuit? Write the formula for resonant frequency. |
12 |
| 717 | If in a transformer the number of turns of primary coil and secondary coil are 5 and 4 respectively and ( 240 mathrm{V} ) is applied to primary coil, then the ratio of current in primary and secondary coil is A .4: 5 B. 5: 4 ( c cdot 5: 10 ) D. 8: 12 |
12 |
| 718 | ( ln ) a ( A C ) circuit the current is given by ( boldsymbol{i}=mathbf{5} sin left(mathbf{1 0 0 t}-frac{boldsymbol{pi}}{mathbf{2}}right) ) and ( boldsymbol{V}= ) ( 200 sin (100 t) V ) then power consumption is ( mathbf{A} cdot 20 W ) в. ( 1000 mathrm{W} ) c. ( 500 W ) D. ( 0 W ) |
12 |
| 719 | resistor R connected 15. The diagram shows a capacitor C and a resistor con in series to an ac source. V, and V2 are voltmeters and is an ammeter Consider now the following statements I. Readings in A and V, are always in phase II. Reading in V, is ahead in phase with reading in V, III. Readings in A and V, are always in phase which of these statements are/is correct (a) I only (b) II only (c) I and II only (d) II and III only |
12 |
| 720 | In the circuit of given figure (1) and (2) are ammeters. Just after key ( boldsymbol{K} ) is pressed to complete the circuit, the reading is A. maximum in both 1 and 2 B. zero in both 1 and 2 c. zero in 1 , minimum in 2 D. maximum in 1, zero in 2 |
12 |
| 721 | For the given circuit, the natural frequency is given by : ( mathbf{A} cdot frac{1}{2 pi} sqrt{L C} ) B. ( frac{1}{2 pi sqrt{L C}} ) ( c cdot sqrt{frac{l}{C}} overline{underline{l}} ) D. ( sqrt{frac{c}{L}} ) |
12 |
| 722 | When ( 4 V ) DC is connected across an inductor, current is ( 0.2 A . ) When ( A C ) of ( 4 V ) is applied the current is ( 0.1 A ) Then self inductance of the coil is: ( left[text { Given } omega=1000 text { rads}^{-1}right] ) A ( .20 mathrm{mH} ) в. ( 40 mathrm{mH} ) c. ( 20 sqrt{3} mathrm{mH} ) D. none of these |
12 |
| 723 | A transformer steps up an ( A C ) supply from ( 220 V ) to ( 2200 V . ) If the secondary coil of the transformer has 2000 turns, the number of turns in its primary coil will be: A . 200 в. 100 c. 50 D. 20 |
12 |
| 724 | In an LCR circuit the potential difference between the terminal of the inductance is ( 60 V ), between the terminals of the capacitor is ( 30 V ) and that between the terminals of the resistance is ( 40 mathrm{V} ). The supply voltage will be equal to: ( mathbf{A} cdot 130 V ) в. ( 10 V ) ( c .50 V ) D. ( 70 V ) |
12 |
| 725 | Statement 1: An emf ( in=€_{0} ) ( sin left(omega t+frac{pi}{6}right) ) is applied in a circuit and a current of ( i=i_{0} sin left(omega t-frac{pi}{3}right) ) flows Then the average power delivered by the source is zero. Statement 2: If the average value of ( in ) |
12 |
| 726 | The self-inductance of the motor of an electric fan is ( 10 mathrm{H} ). In order to impart maximum power at ( 50 mathrm{Hz} ), it should be connected to a capacitance of : (Take ( pi^{2} ) ( =10) ) A ( .4 mu F ) в. ( 8 mu F ) c. ( 1 mu F ) D. ( 2 mu F ) |
12 |
| 727 | An inductor ( 20 mathrm{mH} ), a capacitor ( 100 mu mathrm{F} ) and a resistor ( 50 Omega ) are connected in series across a source of emf, ( mathrm{V}=10 ) ( sin 314 t . ) The power loss in the circuit is? A . 2.74 w в. 0.79 w c. ( 1.13 mathrm{w} ) D. ( 0.43 mathrm{w} ) |
12 |
| 728 | Write any four differences between step-up and step-down transformer |
12 |
| 729 | What is the approximate peak value of an alternating current producing four times the heat produced per seconds by a steady current of ( 2 mathrm{A} ) in a resistor? A ( .2 .8 mathrm{A} ) в. 4.0 А c. 5.6 A D. 8.0 A |
12 |
| 730 | The time taken by the current to rise to 0.63 of its maximum value in a d.C circuit containing inductance ( (boldsymbol{L}) ) and resistance ( (boldsymbol{R}) ) depends on A. ( L ) only B. ( R ) only c. ( frac{L}{R} ) only D. ( L R ) only |
12 |
| 731 | An inductance of ( 2.0 mathrm{H} ),a capacitance of 18 and a resistance of 10 are connected to an ( A C ) source of 20 with adjustable frequency (a) What frequency should be chosen to maximum the current (RMS) in the circuit? (b) What is the value of this maximum current (RMS)? |
12 |
| 732 | What is the phase angle of the source voltage with respect to the current? Does the source voltage lag or lead the current? | 12 |
| 733 | To reduce the resonant frequency in an LCR series circuit with a generator A. the generator frequency should be reduced. B. another capacitor should be added in parallel to the first. C. the iron core of the inductor should be removed. D. dielectric in the capacitor should be removed |
12 |
| 734 | An ( L-C ) circuit consists of an inductor of ( L=0.0900 H ) and a capacitor of ( C=4 times 10^{-4} F . ) The initial charge on the capacitor is ( 5.00 mu C ) and the initial current in the inductor is zero. When the current in the inductor has half its maximum value, what is the energy stored in the inductor? A ( .7 .8 times 10^{-9} J ) B . ( 9.8 times 10^{7} J ) c. ( 7.8 times 10^{7} J ) D. ( 9.8 times 10^{-7} J ) |
12 |
| 735 | In L-C oscillation the maximum charge on the capacitor can be ( Q ). If at any instant, electric energy and magnetic energy associated with the current is equal, then the charge on the capacitor at that instant is : A ( cdot frac{Q}{sqrt{2}} ) в. ( frac{Q}{2} ) c. ( frac{3 Q}{sqrt{2}} ) D. ( frac{3 Q}{2} ) |
12 |
| 736 | An inductance coil of ( 1 H ) and ( a ) condenser of capacity ( 1 p F ) produce resonance. The resonant frequency will be ( ^{text {A }} cdot frac{10^{6}}{pi} H z ) в. ( 27 pi times 10^{6} mathrm{Hz} ) c. ( frac{2 pi}{10^{6}} H z ) D. ( frac{10^{6}}{2 pi} H z ) |
12 |
| 737 | 7. 3. An inductor of inductance L and resistor of resistance R are joined in series and connected by a source of frequency w. Power dissipated in the circuit is 2 (R²+ w²1²) V²R ov (R? + oʻL?) (b) _ V (C) (d) ² & VR² + w²1² (R+ oʻL) (AIEEE 2002) anca of anu transformer is laminated to |
12 |
| 738 | In the electrical network, at ( t<0 ) (as given in the figure), key is placed on (1) till the capacitor got fully charged. Key is placed on (2) at ( t=0 . ) Time when the energy in both the capacitor and the inductor will be same for the first time is A ( cdot frac{pi}{4} sqrt{L C} ) B. ( frac{3 pi}{4} sqrt{L C} ) C ( cdot frac{pi}{3} sqrt{L C} ) D. ( frac{2 pi}{3} sqrt{L C} ) |
12 |
| 739 | A series LCR circuit containing a resistance of ( 120 Omega ) has angular frequency ( 4 times 10^{5} ) rad ( / mathrm{s} ). At resonance the voltages across resistance and inductance are ( 60 mathrm{V} ) and ( 40 mathrm{V} ) respectively. The angular frequency at which the current in the circuit lags the voltage by ( frac{pi}{4} ) is: A ( cdot 2 times 10^{5} r a d / s ) B . ( 6 times 10^{5} mathrm{rad} / mathrm{s} ) c. ( 8 times 10^{5} r a d / s ) D. ( 10 times 10^{5} mathrm{rad} / mathrm{s} ) |
12 |
| 740 | In LCR series circuit, an alternating e.m.f. ‘e’ and current ‘i’ are given by the equations ( e=100 sin (100 t) ) volt, ( i= ) ( mathbf{1 0 0} sin left(mathbf{1 0 0}+frac{boldsymbol{pi}}{mathbf{3}}right) mathrm{m} mathrm{A} . ) The average power dissipated in the circuit will be ( mathbf{A} cdot 100 mathrm{w} ) B. 10w ( c .5 w ) D. 2.5w |
12 |
| 741 | Turn ratio in a setup transformer is ( 1: 2.1 mathrm{f} ) a lechlanche cell of ( 1.5 mathrm{V} ) is connected across the input, what is the voltage across the output? A . ( 1.5 v ) B. 0.0 ( c cdot 3 v ) D. 0.75 ( v ) |
12 |
| 742 | Compute the energy stored in the inductor at ( t=2.00 m s ) A. ( 0.0094 mu J ) B. ( 0.0940 mu J ) c. ( 0.9400 mu J ) D. ( 9.4000 mu J ) |
12 |
| 743 | When induced emf in inductor coil is ( 50 % ) of its maximum value then stored energy in inductor coil in the given circuit will be- A ( .2 .5 m J ) ( mathbf{B} cdot 5 m J ) c. ( 15 m J ) D. 20.5 |
12 |
| 744 | The Figure 26.67 shows variation of ( R ) ( X_{L} ) and ( X_{C} ) with frequency fin a series L, C, R circuit. Then, for what frequency point, the circuit is inductive? ( A ) B. ( c ) ‘. all point |
12 |
| 745 | An A.C. of ( 50 mathrm{Hz} ) and ( 1 mathrm{A} ) peak value flows in primary coil transformer whose mutual inductance is ( 1.5 mathrm{H} ). Then peak value of induced emf in the secondary coil is: A. ( 150 v ) B. ( 150 pi v ) c. ( 300 vee ) D. 200 V |
12 |
| 746 | A ( 120 V, 60 H z ) a.c. power is connected ( 800 Omega ) non-inductive resistance and unknown capacitance in series. The voltage drop across the resistance is found to be ( 102 mathrm{V} ), then voltage drop across capacitor is ( A cdot 8 v ) B. 102v ( c cdot 63 v ) D. ( 55 v ) |
12 |
| 747 | For an ( L C R ) series circuit with an A.C. source of angular frequency ( omega, ) which statement is correct? A cdot circuit will be capacitive if ( omega>frac{1}{sqrt{L C}} ) B. circuit will be capacitive if ( omega=frac{1}{sqrt{L C}} ) c. Power factor of circuit will be unity if capacitive reactance equals inductive reactance D. current will be leading voltage if ( omega>frac{1}{sqrt{L C}} ) |
12 |
| 748 | ( mathbf{A} ) 12 ohm resistor and a 0.21 henry inductor are connected in series to an AC source operating at ( 20 v ) olts, 50 cycle/second. The phase angle between the current and the source voltage is A ( .30^{circ} ) В . ( 40^{circ} ) ( c cdot 80^{circ} ) D. ( 90^{circ} ) |
12 |
| 749 | A voltage of peak value ( 283 mathrm{V} ) and varying frequency is applied to series LCR combination in which ( R=3 Omega, L=25 ) ( mathrm{mH} ) and ( mathrm{C}=400 mu mathrm{F} ). Then the frequency (in ( mathrm{Hz} ) ) of the source at which maximum power is dissipated in the above is A . 51.5 B. 50.7 ( c . ) 51. D. 50.3 |
12 |
| 750 | If resistance of ( 100 Omega ) and the inductance of 0.5 henry and capacitance of ( 10 times 10^{6} ) farad are connected in series through ( 50 mathrm{Hz} ) A.C supp;y, then impedence is A. ( 1.8765 Omega ) B. ( 18.76 Omega ) c. ( 187.6 Omega ) D. 101.3Omega |
12 |
| 751 | The cross-over frequency ( f_{c} ) is A ( cdot frac{1}{2 pi sqrt{L C}} ) B. ( frac{1}{2 pi R C} ) c. ( frac{R}{2 pi I} ) D. none |
12 |
| 752 | A power transformer (step-up) with an 1: 8 turn ratio has ( 60 H z, 120 V ) across the primary; the load in the secondary is ( 10^{4} Omega . ) The current in the secondary is ( mathbf{A} cdot 96 A ) B . ( 0.96 A ) ( c .9 .6 A ) D. ( 96 m A ) |
12 |
| 753 | Complete the diagram of the transformer and connections by labelling all parts joined by you. | 12 |
| 754 | A ( 120 V A C ) line transformer is to supply ( 13000 V ) for a neon sign. To reduce shock hazard a ( 8.5 mathrm{mA} ) fuse is inserted. Find the maximum input power that can be given to the transformer. ( mathbf{A} cdot 120 W ) B. ( 121 W ) ( c cdot 110 W ) D. ( 104 W ) |
12 |
| 755 | A choke coil has negligible resistance. The alternating potential drop across it is 220 volts and the current is ( 5 mathrm{mA} ). The power consumed is A ( cdot 220 times frac{5}{1000} W ) в. ( frac{220}{5} W ) c. zero D. ( 2.20 times 5 W ) |
12 |
| 756 | 57. The total heat produced in resistor Rin an RL circuit when the current in the inductor decreases from 1 to 0 is (a) LI? (b) ELIE |
12 |
| 757 | The primary of a transformer has 400 turns while the secondary has 2000 turns. If the power output from the secondary at ( 1000 V ) is ( 12 k W, ) what is the primary voltage? ( mathbf{A} cdot 200 V ) B. ( 300 V ) c. ( 400 V ) D. ( 500 V ) |
12 |
| 758 | A light bulb is rated at ( 100 W ) for a ( 220 V ) supply. Find the rms current through the bulb: ( mathbf{A} cdot 0.25 A ) в. ( 0.45 A ) c. ( 0.65 A ) D. ( 0.85 A ) |
12 |
| 759 | Two inductors of inductance L each are connected in series with opposite magnetic fluxes. The resultant inductance is (Ignore mutual inductance) A. zero B. c. 2L D. 3L |
12 |
| 760 | has an inductor of inductance ( L ) and a resistor of resistance it connected in series. Using the phasar diagram, explain why the voltage in the circuit will lead the current in phase. (b) The potential difference across the resistor is ( 160 % ) and that across the inductor is ( 120 V . ) Find the effective value of the applied voltage. If the effective current in the circuit be ( 1.0 A ) calculate the total impedance of the circuit. (c) What will be the potential difference in the circuit when direct current is passed through the circuit?? |
12 |
| 761 | In an R-C circuit, select the correct options among the following: This question has multiple correct options A. Instantaneous A.C is given by ( I=I_{0} sin (w t+phi) ) B. The alternating current in the circuit leads the emf by a phase angle C. Its impedance is ( sqrt{R^{2}+(w C)^{2}} ) D. Its capacitive reactance is ( omega C ) |
12 |
| 762 | For the circuit shown in the figure, which of the following statements is true? A. With S1 closed ( V 1=15 V, V 2=20 V ) B. With ( S_{3} ) closed, ( V_{1}=V_{2}=25 mathrm{V} ) C. With ( S_{1} ) and ( S_{2} ) closed, ( V_{1}=V_{2}=0 ) D. With ( S_{1} ) and ( S_{3} ) closed, ( V_{1}=30 vee, V_{2}=20 mathrm{V} ) |
12 |
| 763 | ( A 60 mu F ) capacitor is connected to a 110 ( mathrm{V}(mathrm{rms}), 60 mathrm{Hz} ) ac supply. The rms value of Current in the circuit is: A . 1.49 A B. 14.9 A c. 2.49 A D. 24.9 A |
12 |
| 764 | ITOS ILLUSTRATION 24.2 A voltage, E = 60 sin(314t), is applied across a resistor of 20 92. What will be the reading of Ime (a) in an ac ammeter? (b) in an ordinary moving coil ammeter in series with the resistor? пете! |
12 |
| 765 | The Figure shows a parallel ( L-C-R ) circuit connected to a variable frequency 200V source. L ( =5 mathrm{H}, mathrm{C}=80 mu mathrm{F} ) and ( R=40 Omega ). What is the ems current in the circuit at resonance? ( A cdot 5 A ) B. 10 A c. ( frac{5}{sqrt{2}} ) D. ( 5 sqrt{2} A ) |
12 |
| 766 | In the AC circuit shown, ( X_{L}=7 Omega, R= ) ( 4 Omega ) and ( X_{c}=4 Omega . ) The reading of the ideal voltmeter ( V_{2} ) is ( 8 sqrt{2} ). The reading of idea voltmeter ( V_{1} ) will be : A. 20 volt B. 7 volt ( c cdot 8 ) volt D. 10 volt |
12 |
| 767 | An alternative voltage given by ( V= ) ( 140(sin 314 t) ) is connected across a pure resistor of ( 50 Omega ). Find (i) The frequency of the source. (ii) The rms current through the resistor. |
12 |
| 768 | A circuit element shown in the figure as box is having either a capacitor or an inductor. The power factor of the circuit is ( 0.8, ) which current lags behind the voltage. The source voltage ( V ) |
12 |
| 769 | Find the maximum value of ( boldsymbol{I} ) | 12 |
| 770 | 7. In an LCR series AC circuit, the voltage across each the components, L, C, and R, is 50 V. The voltage across the LC combination will be (a) 50 V (6) 5012 V (c) 100 V (d) 0 V (zero) (AIEEE 2004 |
12 |
| 771 | In an ideal parallel LC circuit, the capacitor is charged by connecting it to a D.C. source which is then disconnected. The current in the circuit A. Becomes zero instantaneously B. Grows monotonically c. Decays monotonically D. oscillates instantaneously |
12 |
| 772 | A transformer has 50 turns in the primary and 1000 turns in the secondary. If the primary is connected to a ( 220 V ) DC supply, what will be the voltage across the secondary? |
12 |
| 773 | A series LCR circuit is tuned to resonance If the angular frequency of the applied AC voltage at resonance is ( omega ), the impedance of the circuit then is: A ( cdot R+omega L+left(frac{1}{omega C}right) ) B. c. ( sqrt{R^{2}+omega L+left(frac{1}{omega C}right)^{2}} ) D. ( sqrt{R^{2}+left(omega L-frac{1}{omega C}right)^{2}} ) |
12 |
| 774 | In which of the following devices, the eddy current effect is not used? A. Induction furnace B. Magnetic breaking in train c. Electromagnet D. Electric heater |
12 |
| 775 | When ( I ) is equal to one half of its maximum value, what is the value of ( |Q| ? ) |
12 |
| 776 | At grid sub-stations the voltage is stepped up to reduce loss of A. current B. electrical energy c. power D. resistance |
12 |
| 777 | A step-down transformer is used to light ( 12 V ) lamp from a ( 240 V ) mains supply. The lamp lights at normal brightness. The primary coil has 600 turns. How many turns are in the secondary |
12 |
| 778 | What is the range between ( f_{1} ) and ( f_{2} ) of an RLC circuit that resonates at ( 150 k H z ) and has a ( Q ) of ( 30 ? ) A . ( 100.0 k H z ) to ( 155.0 k H z ) B. ( 147.5 k H z ) to ( 152.5 k H z ) c. ( 4500 k H z ) to ( 295.5 k H z ) D. ( 149970 H z ) to ( 150030 H z ) |
12 |
| 779 | A choke coil is needed to operate an arc ( operatorname{lamp} operatorname{at} 160 V(mathrm{rms}) ) and ( 50 mathrm{Hz} ). The arc lamp has an effective resistance of ( 5 Omega ) when running at ( 10 A(mathrm{rms}) . ) Calculate the inductance of the choke coil. If the same arc lamp is to be operated on ( 160 V ) DC, what additional resistance would be required. Compare the power losses in both the cases. |
12 |
| 780 | The magnetic field energy in an inductor changes from maximum value to minimum value in ( 5.0 m s, ) when connected to an ( A C ) source. The frequency of the source is ( A cdot 20 H z ) B. 50 Н c. 200 н ( z ) D. 500 нz |
12 |
| 781 | What is resonance circuit? An alternating current circuit consenting L-C-R is connected to a A.C. voltage source in series. Determine: A. Resultant voltage B. Impedance c. Resonance frequency D. None of these above |
12 |
| 782 | If a fully charged capacitor ( C ) with initial charge ( q_{0} ) is connected to a coil of self inductance ( L ) at ( t=0 . ) The time at which the energy is stored equally between the electric field and magnetic field is : A ( . pi sqrt{L C} ) в. ( frac{pi}{4} sqrt{L C} ) c. ( frac{pi}{2} sqrt{L C} ) D. ( frac{pi}{6} sqrt{L C} ) |
12 |
| 783 | Current flowing through the circuit | 12 |
| 784 | Transformer ( rightarrow ) ideal ( rightarrow boldsymbol{E}_{boldsymbol{P}}= ) ( mathbf{1 0 0 0} boldsymbol{V}, boldsymbol{I}_{boldsymbol{P}}=mathbf{5 0 A} ) ( 220 V rightarrow 80 ) houses Resistance of secondary coil will be A . ( 2 Omega ) B. 3Omega ( c .1 Omega ) D. ( 4 Omega ) |
12 |
| 785 | 31. An LCR circuit contains resistance of 100 22 and a supply of 200 V at 300 rad angular frequency. If only capacitance is taken out from the circuit and the rest of the circuit is joined, current lags behind the voltage by 60°. If, on the other hand, only inductor is taken out, the current leads by 60° with the applied voltage. The current flowing in the circuit is (a) 1A (b) 1.5 A (c) 2 A (d) 2.5 A |
12 |
| 786 | A transformer having efficiency of ( 75 % ) is working on ( 220 V ) and ( 4.4 k W ) power supply. If the current in the secondary coil is ( 5 A . ) What will be the voltage across secondary coil and the current in primary coil? ( mathbf{A} cdot V_{s}=220 V, i_{p}=20 A ) B. ( V_{s}=660 V, i_{p}=15 A ) C . ( V_{s}=660 V, i_{p}=20 A ) D. ( V_{s}=220 V, i_{p}=15 A ) |
12 |
| 787 | 0001 155 25. An inductor (L = 0.03 H) 0.03 H 0.15 k92 and a resistor (R = 0.15 k92) are connected in series to a battery of 15 V EMF in a circuit shown below. The key Khas L E been kept closed for a long time. Then at t = 0, K, is opened and key K, is closed simultaneously. At t = 1 ms, the current in the circuit will be (@=150) (a) 100 mA (b) 67 mA (c) 6.7 mA (d) 0.67 mA (JEE Main 2015) |
12 |
| 788 | The reactance of coil when used in an A.C. power supply ( 220volts, 50 cycles/sec) is 50ohms. The inductance of the coil is nearly A . 0.16 Н B. 0.22 c. ( 2.2 mathrm{H} ) D. 1.6 |
12 |
| 789 | An inductor ( 10 Omega / 60^{circ} ) is connected to a ( 5 Omega ) resistance in series. Find net impedance. A . ( 15 Omega ) B. ( 12 Omega ) c. ( 13.2 Omega ) D. ( 18 Omega ) |
12 |
| 790 | The transformer turns ratio is 1: 5 and ( 0.4 mathrm{A} ) current flows through the second when power developed across it is 200 W. Calculate secondary voltage A . 2000 v B. 1500 v c. ( 1000 mathrm{v} ) D. 500 v |
12 |
| 791 | A transformer steps up an AC supply from ( 220 mathrm{V} ) to ( 2200 mathrm{V} ). If the secondary coil of the transformer has 2000 turns,the number of turns in its primary coil will be: A . 200 B. 100 ( c .50 ) D. 20 |
12 |
| 792 | Find the value of an inductance which should be connected in series with a capacitor of ( 5 mu F, ) a resistance of ( 10 Omega ) and an ac source of ( 50 H z ) so that the power factor of the circuit is unity. A ( cdot frac{20}{pi^{4}} ) в. ( frac{20}{pi^{2}} ) c. ( frac{20}{pi^{3}} ) D. ( frac{20}{pi^{5}} ) |
12 |
| 793 | A series R-C circuit is connected to an alternating voltage source. Consider two situation: (a) When capacitor is filled (b) When capacitor is mica filled Current through resister is i and voltage across capacitor is ( V ) then : A ( . V_{a}=V_{b} ) в. ( V_{a}V_{b} ) ( mathbf{D} cdot i_{a}=i_{b} ) |
12 |
| 794 | Assertion In a series ( L C R ) circuit, at resonance condition power consumed by circuit is maximum. Reason At resonance condition, the effective resistance of circuit is maximum. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion c. Assertion is correct but Reason is incorrect D. Both Assertion and Reason are incorrect |
12 |
| 795 | A ( 10 Omega ) resistance, ( 5 mathrm{mH} ) coil and ( 10 mu mathrm{F} ) capacitor are joined in series. When a suitable frequency alternating current source is joined to the combination, the circuit resonates. If the resistance is halved the resonance frequency is A. halved B. doubled c. remains same D. quadrupled |
12 |
| 796 | The transformation ratio of a step up transformer is : A. greater than one B. less than one C. less than one and some times greater than one D. greater than one and some times less than one |
12 |
| 797 | ( ln ) an ( mathrm{AC} ) circuit, ( V ) and ( I ) are given below, then the power dissipated in the circuit: ( V=50 sin (50 t) V, I=50 sin left(50 t+frac{pi}{3}right) m A ) A. ( 0.625 W ) В. ( 1.25 mathrm{W} ) c. ( 2.50 W ) D. ( 5.0 W ) |
12 |
| 798 | For the circuit shown in the Figure, the current through the inductor is ( 0.9 A ) while the current through the condenser is ( 0.4 A ) A. current drawn from generator ( 1=1.13 mathrm{A} ) B. ( omega=frac{1}{(1.5 L C)} ) ( mathbf{C} cdot I=0.5 mathrm{A} ) ( D cdot I=0.6 A ) |
12 |
| 799 | If a capacitor is connected to two different A.C. generators, then the value of capacitive reactance is: A. directly proportional to frequency B. inversely proportional to frequency C. independent of frequency D. inversely proportional to the square of frequency |
12 |
| 800 | ( ln operatorname{an} A C ) circuit ( V ) and ( I ) is given by ( boldsymbol{V}=mathbf{1 0 0 0} sin (mathbf{1 0 0 0} boldsymbol{t}) ) volt ( boldsymbol{I}=mathbf{1 0 0} sin left(mathbf{1 0 0 0} boldsymbol{t}+frac{boldsymbol{pi}}{mathbf{6}}right) boldsymbol{m} boldsymbol{A} ) The power dissipation in the circuit in one complete cycle is. ( mathbf{A} cdot 25 W ) B. ( 25 sqrt{3} ) c. ( 100 mathrm{W} ) D. 10 W |
12 |
| 801 | In a LCR series resonating circle circuit Give the value of average power loss. | 12 |
| 802 | A ( 0.2 Omega ) resistor and ( 15 mu ) rapacitor are connected in series to a ( 220 mathrm{V}, 50 mathrm{Hz} ) ac source. The impedance of the circuit is A . ( 250 Omega ) в. ( 268 Omega ) c. ( 29.15 Omega ) D. ( 291.5 Omega ) |
12 |
| 803 | 22. In the circuit given in the figure, Vc = 50 V and R= 50 S2. The values of C and VR are [vc=50v 110 V 60 Hz R= 50 2 3 (a) 3.3 mF, 60 V (c) 52 uF, 98 V (b) 104 uF, 98 V (d) 2 uF, 60 V |
12 |
| 804 | A step-up transformer of turns ratio 2: 1 has ( 50 mathrm{Hz} ) AC voltage applied to primary The frequency of AC output voltage across secondary is : A. zero B. 25 Hz c. 50 нz D. 100 нz |
12 |
| 805 | Calculate the resonant frequency and ( Q ) factor (Quality factor) of a series L-C-R circuit containing a pure inductor of inductance ( 4 mathrm{H} ), capacitor of capacitance ( 27 mu F ) and resistor of resistance ( 8 cdot 4 Omega ) |
12 |
| 806 | The inductive reactance of a coil is ( 2500 Omega . ) On increasing its selfinductance three times, the new inductive reactance will be A. ( 7500 Omega ) B. 2500 Omega c. ( 1225 Omega ) D. zero |
12 |
| 807 | In a series resonant ( L C R ) circuit, the voltage across ( boldsymbol{R} ) is 100 volts and ( boldsymbol{R}= ) ( 1 k Omega ) with ( C=2 mu F . ) The resonant frequency is 200 rad/s. At resonance the voltage across ( L ) is A. ( 4 times 10^{-3} V ) В. ( 2.5 times 10^{-2} V ) c. ( 40 V ) D. 250 V |
12 |
| 808 | In a parallel L-C-R circuit spring constant ( K ) is analogous to: A . B. ( c cdot 1 / L ) D. ( 1 / c ) |
12 |
| 809 | The capacitive reactance at ( 1600 H z ) is 81 Omega. When the frequency is doubled then capacitive reactance will be A . ( 40.5 Omega ) в. ( 81 Omega ) ( c cdot 162 Omega ) D. Zero |
12 |
| 810 | When resonance is produced in a series ( L C R ) circuit, then which of the following is not correct? A. Current in the circuit is in phase with the applied voltage B. Inductive and capacitive reactance are equal C. If ( R ) is reduced, the voltage across capacitor wil increase D. Impedance of the circuit is maximum. |
12 |
| 811 | If ( 25 W ) of power are applied to the primary of an ideal transformer with a turns ratio of ( 10, ) the power delivered to the secondary load is A ( .25 W ) B. ( 0 W ) c. ( 250 W ) D. ( 2.5 W ) |
12 |
| 812 | State whether given statement is True or False
Apparent power is expressed in watts. |
12 |
| 813 | 6. Alternating current cannot be measured by a DC ammeter because (a) AC cannot pass through DC ammeter (b) AC changes direction (c) the average value of current for complete cycle is zero (d) DC ammeter will get damaged (AIEEE 2004) A … it the oltogo |
12 |
| 814 | The efficiency of a transformer is ( 98 % ) The primary voltage and current are ( 200 V ) and ( 6 A . ) If the secondary voltage is ( 100 V ), the secondary current is : A . ( 11.76 A ) B. ( 12.25 A ) c. ( 3.06 A ) D. ( 2.94 A ) |
12 |
| 815 | An ideal inductor takes a current of ( 10 A ) when connected to a ( 125 V, 50 H z A C ) supply. A pure resistor across the same source takes 12.5 A. If the two are connected in series across a ( 100 sqrt{2} V ) ( 40 H z ) supply, the current through the circuit will be ( mathbf{A} cdot 10 A ) B. ( 12.5 A ) ( c .20 A ) D. ( 25 A ) |
12 |
| 816 | An A.C. of ( 50 mathrm{Hz} ) and ( 1 mathrm{A} ) peak value flows in primary coil transformer whose mutual inductance is ( 1.5 mathrm{H} ). Then peak value of induced emf in the secondary coil is: A. ( 150 v ) B. ( 150 pi v ) c. ( 300 vee ) D. 200 V |
12 |
| 817 | Two resistors are connected in series ( operatorname{across} ) a ( 5 ~ V ) rms source of alternating potential. The potential difference ( operatorname{across} 6 Omega ) resistor is ( 3 V . ) If ( R ) is replaced by a pure inductor ( L ) of such magnitude that current remains same, then the same potential difference ( operatorname{across} L ) is: ( mathbf{A} cdot 1 V ) B. ( 2 V ) c. ( 3 V ) D. ( 4 V ) |
12 |
| 818 | A series LCR-circuit with ( boldsymbol{R}=mathbf{2 0} boldsymbol{Omega} ) ( boldsymbol{L}=mathbf{1 . 5} boldsymbol{H} ) and ( boldsymbol{C}=mathbf{3 5} boldsymbol{mu} mathrm{F} ) is connected to a variable frequency ( 200 V ) ac supply When the frequency of the supply equals the natural frequency of the circuit, the average power transferred to the circuit in one complete cycle is? ( mathbf{A} cdot 200 W ) в. ( 2000 mathrm{W} ) ( c .100 W ) D. ( 4000 mathrm{W} ) |
12 |
| 819 | A step-down transformer is connected to 2400 volts line and 80 amperes of current is found to flow in output load. The ratio of the turns in primary and secondary coil is ( 20: 1 . ) If transformer efficiency is ( 100 % ), then the current flowing in primary coil will be : ( A cdot 8 A ) в. ( 4 A ) ( c .5 A ) D. ( 9 A ) |
12 |
| 820 | State whether given statement is True or False
A reflective load is a load as it appears |
12 |
| 821 | 5. Voltage and current in an ac circuit are given by V = 5 sin ( 1001t – and 1 = 4 sin 1007t +- (a) Voltage leads the current by 30° (b) Current leads the voltage by 30° (c) Current leads the voltage by 60° (d) Voltage leads the current by 60° |
12 |
| 822 | ( 50 H z ) alternative current current of crest value ( 1 A ) flows through the primary of a transformer. If mutual inductance between the primary and secondary is ( 0.5 ~ H, ) then crest voltage induced in the secondary is: ( mathbf{A} cdot 100 V ) B. ( 150 V ) ( mathrm{c} .75 mathrm{V} ) D. ( 50 V ) |
12 |
| 823 | An inductance of negligible resistance whose reactance is ( 22 Omega ) at ( 200 H z ) is connected to 200 volt. If the line frequency is known to be 50 cycles/second, the equation for the line voltage is : A. 0.0175 Henry B. 0.175 Henry c. 1.75 Henry D. 17.5 Henry |
12 |
| 824 | n an L-C-R circuit as shown both switches are open initially. Now switch ( S_{1} ) and ( S_{2}, ) are closed. ( (q ) is the charge on the capacitor and ( r=R C ) is capacitance time constant). What is the charge on the capacitor at ( t=2 tau ? ) |
12 |
| 825 | In a series ( L, R, C ) circuit which is connected to ac source, when resonance is obtained then net impedance Z will be: A ( . Z=R ) B. ( quad Z=omega L-frac{1}{omega C} ) ( mathbf{c} cdot Z=omega L ) D. ( z=frac{1}{w C} ) |
12 |
| 826 | State whether given statement is True or False The circuit phase angle is the angle between the total current and the applied (source) voltage. A. True B. False |
12 |
| 827 | 11. In a series resonant LCR circuit, the voltage across R is 100 V and R = 1 k12 with C = 2 uF. The resonant frequency ois 200 rad/s. At resonance the voltage across L is (a) 250 V (b) 4 x 10-3 v (c) 2.5 x 10-2 V (d) 40 V (AIEEE 2006) A gonerator coil with turns oul of the come |
12 |
| 828 | The reading shown in AC Voltmeter when ( mathrm{S} ) is moved to ( mathrm{B} ) is: A . ( 120 v ) B. 100 ( v ) ( c cdot 140 v ) D. ( 160 mathrm{V} ) |
12 |
| 829 | ( ln ) an oscillating ( L-C ) circuit in which ( C=4.00 mu F, ) the maximum potential across the capacitor during the oscillations is ( 1.50 V ) and the maximum current through the inductor is ( 50.0 m A ) What is the inductance ( L ? ) ( mathbf{A} cdot 8.6 m H ) в. ( 3.6 m H ) c. ( 6.6 m H ) D. ( 4.6 m H ) |
12 |
| 830 | To produce an ( 800 H z ) sine wave, a four pole generator must be operated at A. 200 rps в. 400 rps c. 800 rps D. 1,600 rps |
12 |
| 831 | State whether True or False: A series resonant circuit is commonly called a tank circuit. A. True B. False |
12 |
| 832 | Identify the graph which correctly represents the variation of capacitive reactance ( X_{C} ) with frequency. ( A ) B. ( c ) D. |
12 |
| 833 | A DC circuit contains ( 10 Omega ) of resistance in series with ( 10 H ) coil. The impedance of the circuit is A . ( 10 Omega ) B. 20Omega c. ( 1 Omega ) D. zero |
12 |
| 834 | Which of the following in electricity is analogous to momentum ( m v ) in dynamics? A. IV B . IL c. ( mathrm{Q} ) D. IQ |
12 |
| 835 | The voltage in the primary and the secondary coils of a step up transformer are ( 200 mathrm{V} ) and ( 4 mathrm{KV} ) respectively. If the current in the primary is 1 ampere then the current in the secondary coil will be ( A cdot 50 mathrm{m} ) A B. 500 ( mathrm{m} ) A ( c cdot 5 A ) ( D cdot 5 m A ) |
12 |
| 836 | An inductor coil stores ( U ) energy when ( i ) current is passed through it and dissipates energy at the rate of ( P . ) The time constant of the circuit, when this coil is connected across a battery of zero internal resistance is : A ( cdot frac{4 U}{P} ) в. ( frac{U}{P} ) c. ( frac{2 U}{P} ) D. ( frac{2 P}{U} ) |
12 |
| 837 | A capacitor ‘C’, a variable resistor’R’ and a bulb ‘B’ are connected in series to the ac mains in circuit as shown. The bulb glows with some brightness. How will the glow of the bulb change if (i) a dielectric slab is introduced between the plates of the capacitor, keeping resistance ( R ) to be the same; (ii) the resistance ( R ) is increased keeping the same capacitance? |
12 |
| 838 | A transmitter transmits at a wavelength of ( 300 m . ) A condenser of capacitance ( 2.4 mu F ) is being used. The value of the inductance for the resonant circuit is approximately ( mathbf{A} cdot 10^{-4} H ) в. ( 10^{-6} H ) c. ( 10^{-8} H ) D. ( 10^{-10} mathrm{H} ) |
12 |
| 839 | If in a transformer the number of turns of primary coil and secondary coil are 5 and 4 respectively and ( 240 mathrm{V} ) is applied to primary coil, then the ratio of current in primary and secondary coil is : A .4: 5 B. 5: 4 c. 5: 10 D. 8: 12 |
12 |
| 840 | In series L-C-R resonant circuit, to increase the resonant frequency: A. ( L ) will have to be increased B. C will have to be increased c. LC will have to be decreased D. LC will have to be increased |
12 |
| 841 | With increase in frequency of an A.C. supply, the inductive reactance A. decreases B. increases directly with frequency C. increases as square of frequency D. decreases inversely with frequency |
12 |
| 842 | 61. A telephone wire of length 200 km has a capacitance of 0.014 uF per km. If it carries an ac of frequency 5 kHz, what should be the value of an inductor required to be connected in series so that the impedance of the circuit is minimum (a) 0.35 mH (b) 35 mH (c) 3.5 mH (d) Zero |
12 |
| 843 | ( ln ) a circuit ( L, C, R ) are connected in series with an alternating voltage source of frequency ( f ). The current lags the voltage by ( 45^{0} . ) The value of ( C ) is: A ( cdot frac{1}{pi f(2 pi f L+R)} ) B・ ( frac{1}{2 pi f(2 pi f L-R)} ) c. ( frac{1}{2 pi f(2 pi f L+R)} ) D. ( frac{1}{pi f(2 pi f L-R)} ) |
12 |
| 844 | ( ln operatorname{an} A C ) circuit ( V ) and ( I ) are given ( V= ) ( 100 sin (100 t) V ) and ( I= ) ( mathbf{1 0 0} sin (mathbf{1 0 0} t+boldsymbol{pi} / mathbf{3}) boldsymbol{m m} . ) The power dissipated in the circuit is: A ( cdot 10^{4} ) watt B. 10 watt c. 2.5 watt D. 5 watt |
12 |
| 845 | Draw a curve for showing variation in alternating current with frequency in LCR resonant circuit. Hence obtain an expression of bandwidth. |
12 |
| 846 | For the circuit shown in the figure the current through the inductor is ( 1.6 A ) while the current through the condenser is ( 0.4 A ), then the current ( l ) drawn from the source is : A ( cdot 2 sqrt{2} A ) B. ( 1.65 A ) ( c .1 .2 A ) D. 2.0 |
12 |
| 847 | In the circuit shown in figure, This question has multiple correct options A ( cdot V_{R}=80 V ) В. ( X_{C}=50 Omega ) c. ( V_{L}=40 V ) D. ( V_{0}=100 V ) |
12 |
| 848 | ov 80. A circuit containing capacitors C and CZ as shown in the figure are in steady state with key K, closed. At the instant 1 = 0, if K, is opened and K is closed then the maximum current in the circuit will be 1.= 2 uF C2 = 2 uF Kzoo (a) 1A 0000000 L = 0.2 mH (b) A (d) None (c) 24 |
12 |
| 849 | In a series LCR circuit ( mathbf{R}=200 ) Omega and the voltage and the frequency of the main supply is ( 220 mathrm{V} ) and ( 50 mathrm{Hz} ) respectively. On taking out the capacitance from the circuit the current lags behind the voltage by ( 30^{0} ) On taking out the inductor from the circuit the current leads the voltage by ( 30^{0} . ) The power dissipated in the LCR circuit is A . ( 305 mathrm{W} ) B. ( 210 mathrm{W} ) c. ZeroW D. ( 242 mathrm{W} ) |
12 |
| 850 | The current in the shown circuit is found to be ( 4 sin left(314 t-frac{pi}{4}right) A ). Find the value of inductance | 12 |
| 851 | The instantaneous potential difference between points ( A ) and ( B ) is : A ( cdot 8 sin left(50 pi t+37 frac{pi}{180}right) ) B ( cdot 8 sin left(50 pi t-37 frac{pi}{180}right) ) c. ( 10 sin (50 pi t) ) D. ( 10 cos (50 pi t) ) |
12 |
| 852 | Power loss (in W) in case of dc is | 12 |
| 853 | A capacitor of capacitance ( 2 mu F ) is connected in the tank circuit of an oscillator oscillating with a frequency of 1 kHz. If the current flowing in the circuit is ( 2 mathrm{mA} ), the voltage across the capacitor will be : A . ( 0.16 mathrm{v} ) B. 0.32 c. 79.5 ( v ) D. ( 159 mathrm{V} ) |
12 |
| 854 | A choke coil and capacitor are connected in series and the current through the combination is maximum for ( A C ) of frequency ( n ). If they are connected in parallel, at what frequency is the current through the combination minimum? ( A ) в. ( n / 2 ) ( c cdot 2 n ) D. None of these |
12 |
| 855 | 15 s, elf- 10. The self-inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of (a) 2 ur (b) 1 uF (c) 8 uF (d) 4uF (AIEEE 2005) 13) in |
12 |
| 856 | The r.m.s current in an ac circuit is ( 1 A ) If the watt less current be ( sqrt{3} A ), Then what is the power factor |
12 |
| 857 | ( ln ) a circuit ( L C=10^{-3} H, C=10^{-3} F ) Find angular frequency. A. 1000 rad ( / ) sec B. 100 rad/sec c. 10 rad ( / ) sec D. ( 10^{-3} )rad( / )sec |
12 |
| 858 | If we change the value of ( R ), then A. Voltage does not change on ( L ) B. Voltage does not change on LC combination C. Voltage does not change on ( mathrm{C} ) D. Voltage change on LC combination |
12 |
| 859 | When an AC voltage of ( 220 mathrm{V} ) is applied to the capacitor ( C ), then A. the maximum voltage between plates is 220 v. B. the current is in phase with the applied voltage c. the charge on the plate is not in phase with the applied voltage D. power delivered to the capacitor per cycle is zero |
12 |
| 860 | In the circuit shown in the figure, the A.C. source gives a voltage ( V=20 cos ) ( (2000 mathrm{t}) ) volt. Neglecting source resistance, select correct alternative(s). This question has multiple correct options A. The reading of voltmeter is 0 V B. The reading of voltmeter is 5.6 C. The reading of ammeter is 1.4 A D. The reading of ammeter is 0.47 A |
12 |
| 861 | A certain series resonant circuit has a bandwidth of ( 2 k H z . ) If the existing coil is replaced with one having a higher value of ( Q, ) the bandwidth will A. Increase B. Remain the same c. Decrease D. Be less selective |
12 |
| 862 | In an oscillating ( L-C ) circuit in which ( C=4.00 mu F, ) the maximum potential across the capacitor during the oscillations is ( 1.50 V ) and the maximum current through the inductor is ( 50.0 m A ) How much time does the charge on the capacitor take to rise from zero to its maximum value? A. ( 0.238 mathrm{ms} ) B. ( 0.788 mathrm{ms} ) c. ( 0.488 mathrm{ms} ) D. ( 0.188 mathrm{ms} ) |
12 |
| 863 | The reactance at a circuit Is zero. it Is possible mat me circuit contains This question has multiple correct options ( A . ) an inductor and a capacitor B. an inductor but no capacitor C. so a capacitor but no inductor D. neitherr an inductor nor a capacitor |
12 |
| 864 | The capacitive reactance of a condenser of capacity ( 25 mu mathrm{F} ) for an ( mathrm{AC} ) of frequency ( 4000 mathrm{Hz} ) will be A ( cdot frac{5}{pi} Omega ) в. ( frac{10}{pi} Omega ) c. ( 5 pi Omega ) D. ( frac{pi}{5} Omega ) |
12 |
| 865 | A step down transformer reduces ( 220 mathrm{V} ) to ( 11 mathrm{V} ).The primary coil draws ( 5 mathrm{A} ) current and secondary coil supplies 90A.Efficiency of the transformer will be A . 4.4% B. 20% c. 33% D. 90% |
12 |
| 866 | In a series LCR circuit at resonance, the appiled ac voltage is ( 220 mathrm{V} ). If bthe potential drop across the inductance is ( 110 V, ) then the potential drop across the resistance is A ( cdot 110 sqrt{2} V ) B. ( 110 V ) c. ( 220 V ) D. ( 220 sqrt{2} V ) |
12 |
| 867 | A transformer consists of a coil of 1200 turns and another coil, with a total of 120 turns, which can be tapped at various places. Primary voltage is ( 240 mathrm{V} ) At which pair of terminals would you connect to a ( 12 mathrm{V}, 24 mathrm{V} ) lamp for it to be lit normally? |
12 |
| 868 | A ( 2 F ) capacitor is initially charged to ( 20 V ) and then shorted across a ( 5 m H ) inductor. The angular frequency of oscillation is. A. ( 1000 mathrm{rad} / mathrm{s} ) B. 100 rad/s c. ( 10000 mathrm{rad} / mathrm{s} ) D. ( 10 mathrm{rad} / mathrm{s} ) |
12 |
| 869 | In modern days incoming frequency of radio receiver is superposed with a locally produced frequency produce intermediate frequency which is always constant. This makes tuning of the receiver very simple. This is used in superheterodyne oscillators. |
12 |
| 870 | In a transformer the output current and voltage are ( 4 mathrm{A} ) and ( 20 mathrm{V} ) respectively. If the ratio of number of turns in the primary and secondary coil is 2: 1 respectively, what is the input current and voltage ? ( A cdot 2 A ) and 40 B. 1 A and 20 c. 4 A and ( 10 v ) D. 8 A and 40 v |
12 |
| 871 | ( 0.21-H ) inductor and ( a 88-Omega ) ( mathbf{A} ) resistor are connected in series to a ( 220-V, 50-H z A C ) source. The current in the circuit and the phase angle between the current and the source voltage are respectively. Use ( boldsymbol{pi}=mathbf{2 2} / mathbf{7} ) A ( cdot 2 A, tan ^{-1} 3 / 4 ) B. ( 14.4 A, tan ^{-1} 7 / 8 ) c. ( 14.4 A, tan ^{-1} 8 / 7 ) D. ( 3.28 A, tan ^{-1} 2 / 11 ) |
12 |
| 872 | 13. In an AC circuit, the voltage applied is E = E, sin ot. The resulting current in the circuit is I = 1, sin (ot – T/2). The power consumption in the circuit is given by e Eolo (a) P=0 (b) P= 2 (c) P= V2 Eolo (d) P= O (AIEEE 2007) Tonna noon |
12 |
| 873 | In a transformer the number of turns of primary coil and secondary coil are 2.5 and 2 respectively and ( 140 mathrm{V} ) is applied on primary coil, then find the ratio of current in primary and secondary coils: A ( cdot I_{p}: I_{s}=4: 5 ) B . ( I_{p}: I_{s}=5: 4 ) ( mathrm{c} cdot I_{p}: I_{s}=4: 3 ) D. ( I_{p}: I_{s}=3: 5 ) |
12 |
| 874 | The resonant frequency of the given RLC circuit. |
12 |
| 875 | 52. Figure shows an iron-cored transformer assumed to be Primary coil 100% efficient. The ratio of Secondary 6.0.2 coil the secondary turns to the primary turns is 1:20. A 240 V ac supply is connected to the primary coil and a 6 12 resistor is connected to the secondary coil. What is the current in the primary coil? (a) 0.10 A (b) 0.14 A (c) 2 A (d) 40 A |
12 |
| 876 | In a circuit, the frequency is ( boldsymbol{f}=frac{mathbf{1 0 0 0}}{mathbf{2} pi} ) ( mathrm{Hz} ) and the inductance is 2 henry, then the reactance will be ( A cdot 200 Omega ) в. 200 ( mu ) Omega c. ( 2000 Omega ) D. 2000 ( mu Omega ) |
12 |
| 877 | The core of a transformer is laminated to reduce A. flux leakage B. hysteresis c. copper loss D. eddy current |
12 |
| 878 | In an LC circuit the capacitor has maximum charge qo. The value of ( left(frac{d I}{d t}right)_{max } ) A ( cdot frac{q_{0}}{L C} ) в. ( frac{q_{0}}{sqrt{L C}} ) c. ( frac{q_{0}}{L C}-1 ) D. ( frac{q_{0}}{L C}+1 ) |
12 |
| 879 | 1. If i = 12; 0<t<T then r.m.s. value of current is 72 (d) None of these |
12 |
| 880 | Compare a step-up transformer with a step-down transformer based on the number of loops in the primary and secondary coils. | 12 |
| 881 | The incorrect statement for L-R-C series circuit is A. The potential difference across the resistance and the appleid e.m.f. are always in same phase B. The phase difference across inductive coil is ( 90^{circ} ) C. The phase difference between the potential difference across capacitor and potential difference across inductance is ( 90^{circ} ) D. The phase difference between potential difference across capacitor and potential difference across resistance is ( 90^{circ} ) |
12 |
| 882 | The alternating current in a circular is described by the graph as shown in figure. The rms current obtained from the graph would be A ( cdot 1.4 mathrm{A} ) B. 2.2 A ( c cdot 1.6 A ) D. 2.6 A |
12 |
| 883 | 2. In a transformer, the number of turns in the primary are 140 and that in the secondary are 280. If the current in primary is 4 A, then that in the secondary is (a) 4A (b) 2 A (c) 6A (d) 10 A (AIEEE 2002) |
12 |
| 884 | 38. A sinusoidal ac current flows through a resistor of resistanceR. If the peak current is Ip, then the power dissipated is (a) 1Rcos e (b) IR (d) – BR WUL A 2011 bediib uoltolto |
12 |
| 885 | Which of the following combinations should be selected for better tuning of an L-C-R circuit used for communication? A. ( R=20 Omega, L=1.5 mathrm{H}, mathrm{C}=35 mu F ) B. ( R=25 Omega, L=2.5 mathrm{H}, mathrm{C}=40 mu F ) c. ( R=15 Omega, L=3.5 mathrm{H}, mathrm{C}=30 mu F ) D. ( R=25 Omega, L=1.5 mathrm{H}, mathrm{C}=45 mu F ) |
12 |
| 886 | In an L-C-R series circuit, at resonance A. the current and voltage are in phase B. the impedance is maximum c. the current is minimum D. the quality factor is Independent of R E ( cdot ) the current leads the voltage by ( frac{pi}{2} ) |
12 |
| 887 | A step-down transformer with an efficiency of ( 80 % ) is used on a 1000 v line to deliver ( 10 mathrm{A} ) at ( 100 mathrm{V} ) at the secondary coil. The Current drawn from the line is A . ( 1.5 mathrm{A} ) B. 2 A ( c cdot 3 A ) D. 1.25 A E. 1 A |
12 |
| 888 | An ( L-C-R ) series circuit with ( L= ) ( 0.120 H, R=240 Omega, ) and ( C=7.30 mu F ) carries an rms current of ( 0.450 A ) with a frequency of ( 400 H z . ) What is the average rate at which electrical energy is dissipated (converted to other forms) in the inductor? |
12 |
| 889 | 26. An LCR circuit is equivalent to a damped pendulum. In an LCR circuit the capacitor is charged to go and then connected to the Land R as shown below: If a student plots graphs of the square of maximum charge (Q Max) on the capacitor with time (t) for two different values L, and L2 (L,>L) of L then which of the following represents this graph correctly? (Plots are schematic and not drawn to scale) Oʻmax! gmax (a) 24 (b) max max Q (for both L and L) (JEE Main 2015) |
12 |
| 890 | The peak voltage of an ac supply is ( 300 V . ) What is the rms voltage? | 12 |
| 891 | Power consumed in an AC circuit becomes zero if A. inductance and resistance are both high. B. inductance and resistance are both low. C. inductance is very high and resistance is negligible. D. inductance is low and resistance is high. |
12 |
| 892 | In the given figure, the instantaneous value of the alternating e.m.f is ( e= ) 14.14sinwt. The voltmeter reading in volts will be: ( mathbf{A} cdot 141.4 ) B. 10 c. 200.0 D. 70.7 |
12 |
| 893 | What is ( Q ) factor of a RC circuit? A ( cdot frac{1}{R} ) в. ( frac{X_{C}}{R} ) ( c .1 ) D. |
12 |
| 894 | 20. A 50 W, 100 V lamp is to be connected to an ac mains of 200 V, 50 Hz. What capacitor is essential to be put in series with the lamp? (6) 30 tv5UF 100 (c) uF |
12 |
| 895 | The secondary windings of a transformer in which the voltage is stepped down are usually made of thicker wire than the primary. Explain why. | 12 |
| 896 | The ratio of turns in the transformer is given as ( 2: 3 . ) If the current passing through the primary coil is 3 A. Find the current through the load resistance: A. ( 4.5 mathrm{A} ) B. 1.5 A ( c cdot 2 A ) D. 1 A |
12 |
| 897 | In which of the following circuit, there may be no change in current with increase in the frequency when same ac current is passed through them: ( A ) B. (b) ( c ) D. |
12 |
| 898 | A resistance of ( 10 Omega ) and an inductance of ( 100 m H ) are connected in series with an AC source of voltage ( boldsymbol{V}= ) ( 100 cos (100 t) ) volt. The phase difference between the voltage applied and the current flowing in the circuit will be A . zero в. ( frac{pi}{2} ) c. D. ( pi ) |
12 |
| 899 | In a transformer, the number of turns in the primary coil is 140 and that in the secondary coil is ( 280 . ) If the current in the primary coil is ( 4 A ), then that in the secondary coil is ( A cdot 4 A ) B. 2 A ( c cdot 6 A ) D. 10 A |
12 |
| 900 | An electronic test circuit produced a resonant curve of half power frequency points at ( 414 H z ) and ( 436 H z ). If ( Q ) factor be ( 10, ) the resonant frequency of the circuit is: A ( .220 H z ) B. ( 22 H z ) c. ( 2.2 H z ) D. ( 0.22 H z ) |
12 |
| 901 | The circuit shown below acts as: A. Tuned filter B. Low pass filter c. High pass filter D. Rectifier |
12 |
| 902 | The phase relationships between the voltages across the inductor, the capacitor and the source. | 12 |
| 903 | The natural frequency of the circuit shown in adjoining figure is A ( cdot frac{1}{2 pi sqrt{L C}} ) в. ( frac{1}{2 pi sqrt{2 L C}} ) c. ( frac{2}{2 pi sqrt{L C}} ) D. zero |
12 |
| 904 | ( ln ) an ( L C ) circuit the capacitor has maximum charge ( q_{0} . ) The value of ( left(frac{d I}{d t}right)_{max }, ) where ( I ) is current in the circuit and ( t ) is time, is ( ^{A} cdot frac{q_{0}}{L C} ) в. ( frac{q_{0}}{sqrt{L C}} ) c. ( frac{q_{0}}{L C}-1 ) D. ( frac{q_{0}}{L C}+1 ) |
12 |
| 905 | In a step-up transformer, if ratio of truns of primary to secondary is 1: 10 and primary voltage is ( 230 V ). If the load current is ( 2 A ), then the current in primary is A . ( 20 A ) в. ( 10 A ) ( c . $ 2 A ) D. ( 1 A ) |
12 |
| 906 | Draw the graphs showing variation of Inductive reactance and Capacitive reactance with frequency of applied A.C source. |
12 |
| 907 | The capacitor offers zero resistance to A. D.C. only B. A.C. & D.C. c. A.C. only D. neither A.C. nor D.C. |
12 |
| 908 | An AC source is connected to a purely resistive circuit. What is true of the following A. current leads ahead of voltage in Phase B. current lags behind voltage in phase c. current and voltage are in same Phase D. any of the above may be true depending upon the value of resistance |
12 |
| 909 | The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of ( 20 vee, 50 ) Hz. What will be the output of the secondary? |
12 |
| 910 | What is resonant electrical circuit? What are its types? Find out an expression for resonant frequency for series L-C-R circuit. |
12 |
| 911 | In an RLC series circuit shown in figure, the readings of voltmeters ( V_{1} ) and ( V_{2} ) are ( 100 mathrm{V} ) and ( 120 mathrm{V}, ) respectively. The same voltage is ( 130 mathrm{V} ). For this situation, mark out the incorrect statement. A. Voltage across resistor, inductor and capacitor are 50 ( vee, 50 sqrt{3} mathrm{V} ) and ( 120+50 sqrt{3} mathrm{V}, ) respectively B. Voltage across resistor. inductor and capacitor are 50 V, ( 50 sqrt{3} ) V and ( 120-50 sqrt{3} ) V, respectively c. Power factor of the circuit is ( 5 / 13 ) D. The circuit is capacitance in nature |
12 |
| 912 | If the values of inductance and frequency in an AC circuit are 2 henry and ( frac{10^{3}}{2 pi} ) Hz respectively then the value of inductive reactance will be A ( cdot frac{2 times 10^{3}}{pi} Omega ) B . ( 2 times 10^{2} Omega ) ( c cdot 10^{3} Omega ) D. ( 2 times 10^{3} Omega ) |
12 |
| 913 | In transformer, power of secondary A. less than primary coil B. more than primary coil C. more in step up and less in step primary coil D. same in both primary and secondary coil |
12 |
| 914 | The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux linked with the primary coil is given by ( phi=phi_{0}+4 t, ) where ( phi ) is in webers, tis time in seconds and ( phi_{0} ) is a constant, the output voltage across the secondary coil is: A. 30 volts B. 90 volts c. 120 volts D. 220 volts |
12 |
| 915 | V sin [ax + (14) 55. A current source sends a current I = 1, cos(ot). When connected across an un- known load, it gives a a voltage output of V = Load Vo sin[ot +(Td/4)] across that load. Then the voltage across the cur- rent source may be brought in phase with the current through it by (a) connecting an inductor in series with the load (b) connecting a capacitor in series with the load (c) connecting an inductor in parallel with the load (d) connecting a capacitor in parallel with the load |
12 |
| 916 | A charged ( 30 mu mathrm{F} ) capacitor is connected to a ( 27 mathrm{mH} ) inductor. What is the angular frequency of free oscillations of the circuit? |
12 |
| 917 | 10. Find out the current flown through the wire at t= – second. (a) 4.5 Amp (b) 4.573 Amp (c) V2 Amp (d) 9 Amp |
12 |
| 918 | A fascinating behaviour of the series RLC circuit is the phenomenon of resonance. a) Explain Resonance in an LCR circuit. b) Draw a graphical representation of variation of current amplitude ( i_{m} ) with frequency ( omega ) c) What do you mean by sharpness of resonance? Explain it. |
12 |
| 919 | A inductance capacitance circuit is in the state of resonance. if the ( C=0.1 mu F ) and ( boldsymbol{L}=mathbf{0 . 2 5} ) Henry. Neglecting ohmic resistance of circuit what is the frequency of oscillations A. ( 1007 mathrm{Hz} ) в. ( 100 mathrm{Hz} ) ( mathrm{c} .109 mathrm{Hz} ) D. ( 500 H z ) |
12 |
| 920 | 51. In the shown AC circuit phase different between cur I, and I, is Xc mm R Ein Rio ton-1 X ₂ – X c I |
12 |
| 921 | A pure resistance is connected as shown in the figure. The phase difference between the voltage applied and the current flowing in it will be A . zero в. ( frac{pi}{2} ) ( c cdot-frac{pi}{2} ) D. ( frac{pi}{4} ) |
12 |
| 922 | In an ideal transformer turn ratio is 2: 3 If input voltage is ( 100 mathrm{V} / 60 mathrm{Hz} ), then output voltage is A . 150 V/90 нz ( z ) z B. 150 V/40 нZ c. ( 150 vee / 60 ) Н ( z ) D. 66.6 V/60 нz |
12 |
| 923 | An AC circuit contains a variable inductor ( L, ) connected in series with a light bulb of resistance ( R ) as shown Assume that the resistance of the light bulb is independent of its temperature. Now it is desired to reduce the power of the light bulb to one fourth then (frequency of ac source is ( frac{R}{2 pi L_{0}} ) wher This question has multiple correct options A. Power factor of the circuit should be reduced to half B. Inductance of the circuit should be increased by a factor of ( sqrt{3} ) c. Impedance of the circuit should be increased by a factor of 4 D. R.M.S. current in the circuit should be reduced to half |
12 |
| 924 | In medium wave broadcast a radio can be tuned in the frequency range 800 ( mathrm{kHz} ) to ( 1200 mathrm{kHz} ). In L-C circuit of this radio effective inductance is ( 200 mu H ) what should be the range of the variable capacitor? ( A cdot 88 ) pF to 198 pF B. 98 pF to 198 pF C. 78 pF to 146 pF D. 20 pF to 112 pF |
12 |
| 925 | A series LCR circuit consists of an inductor L a capacitor ( C ) and a resistor ( R ) connected across a source of emf ( varepsilon= ) ( varepsilon_{0} sin omega t . ) When ( omega L=frac{1}{omega C} ) the current in the circuit is ( l_{0} ) and if angular frequency of the source is changed to ( omega ) ‘, the current in the circuit becomes ( frac{l_{0}}{2}, ) then the value of ( left|boldsymbol{omega}^{prime} boldsymbol{L}-frac{mathbf{1}}{omega^{prime} boldsymbol{C}}right| ) is ( A ) B. ( sqrt{3} ) R ( c cdot sqrt{15} ) |
12 |
| 926 | An LC circuit has ( L=5 mathrm{mH} ) and ( C=20 mu mathrm{F} ) ( boldsymbol{v}=mathbf{5} times mathbf{1 0}^{-mathbf{3}} ) coswt is supplied. is twice the resonant frequency. Find the maximum charge stored in the capacitor: A. 66.6 nc B. 11.3 nc c. 23.2 nc D. 33.3 nç |
12 |
| 927 | a rms 1.TI .UT 10. An ac source of angular frequency ois fed across a resistor r and a capacitor C in series. The current registered is I. If now the frequency of source is changed to 0/3 (but maintaining the same voltage), the current in then circuit is found to be halved. Calculate the ratio of reactance to resistance at the original frequency o (b) VE d) |
12 |
| 928 | A circuit has a self-inductance of ( 1 boldsymbol{H} ) and carries a current of ( 2 A . ) To prevent sparking, when the circuit is switched off, a capacitor which can withstand ( 400 V ) is used. The least capacitance of the capacitor connected across the switch must be equal to A. ( 50 mu F ) B. ( 25 mu F ) c. ( 100 mu F ) D. ( 12.5 mu F ) |
12 |
| 929 | ( mathbf{A} mathbf{7} mathbf{5} mathbf{0} boldsymbol{H} boldsymbol{z}, mathbf{2 0} boldsymbol{V} ) source is connected to a resistance of ( 100 Omega, ) an inductance of ( 0.1803 H ) and a capacitance of ( 10 mu F ) all in series. The time in which the resistance (thermal capacity ( left.=2 J /^{0} Cright) ) will get heated by ( 10^{0} C ) is A . 348 s B. 328 s c. 248 s D. 228 |
12 |
| 930 | In a series ( L C R ) circuit the frequency of a ( 10 V, A C ) voltage source id adjusted in such a fashion that the reluctance of the inductor or measures ( 15 Omega ) and that of the capacitor ( 11 Omega . ) If ( R=3 Omega, ) the potential difference across the series combination of ( L ) and ( C ) will be: ( A cdot 8 V ) B. ( 10 V ) ( c cdot 22 V ) D. ( 52 V ) |
12 |
| 931 | A current of ( 5 A ) is flowing at ( 220 V ) in the primary coil of a transformer. If the voltage produced in the secondary coil is ( 2200 V ) and ( 50 % ) of power is lost, then the current in the secondary will be A . ( 2.5 A ) в. ( 0.5 A ) c. ( 0.25 A ) D. ( 5 A ) |
12 |
| 932 | A sinusoidal voltage of peak value ( 293 mathrm{V} ) and frequency ( 50 mathrm{Hz} ) is applied to a series LCR circuit in which ( mathrm{R}=6 Omega, mathrm{L} ) ( =25 mathrm{mH} ) and ( mathrm{C}=750 mu mathrm{F} ). The impedance of the circuit is: A. ( 7.0 Omega ) B. ( 8.9 Omega ) ( c cdot 9.9 Omega ) D. 10.0 ( Omega ) |
12 |
| 933 | An oscillating circuit contains an inductor of inductance ( 10^{-6} mathrm{H} ) and two capacitor each of capacitance ( 5 times 10^{-6} ) farad connected in parallel. Then the resonance frequency of the circuit is A ( cdot frac{10^{5}}{2 pi} ) B. ( frac{10^{5}}{pi} ) c. ( frac{3 times 10^{5}}{2 pi} ) D. ( frac{sqrt{2 times 10^{5}}}{pi} ) |
12 |
| 934 | A step down transformer is connected to 2400 volts line and 80 amperes of current is found to flow in output load. The ratio of the turns in primary and secondary coil is ( 20: 1 . ) If the transformer efficiency is ( 100 % ), then the current flowing in the primary coil will be ( mathbf{A} cdot 1600 mathrm{amp} ) B. 20 amp c. 4 amp D. 1.5 amp |
12 |
| 935 | ( ln ) an ( A C ) circuit voltage ( V=V_{0} sin w t ) and inductor L is connected across the circuit. Then the instentaneous power will be A ( cdot frac{V_{0}^{2}}{2 w l} sin w t ) B. ( frac{-V_{0}^{2}}{2 w l} sin w t ) c. ( frac{V_{0}^{2}}{2 w l} sin 2 w t ) D. ( frac{V_{0}^{2}}{w l} sin w t ) |
12 |
| 936 | The transformation ratio of a transformer is ( 10: 1 . ) The current in the primary circuit if the secondary current required is 100 A assuming the transformer be ideal, is ( A cdot 500 A ) B. 200 A ( c cdot 1000 A ) D. 2000 A |
12 |
| 937 | The capacitance in an oscillatory LC circuit is increased by ( 1 % ). The change in inductance required to restore its frequency of oscillation is to A. decrease it by 0.5% B. increase it by 1% c. decrease it by 1% D. decrease it by ( 2 % ) |
12 |
| 938 | In a series LCR circuit ( boldsymbol{R}=mathbf{3 0 0 Omega}, boldsymbol{L}= ) ( mathbf{0 . 9 H}, boldsymbol{C}=mathbf{2} boldsymbol{mu} boldsymbol{F}, boldsymbol{omega}=mathbf{1 0 0} mathbf{o} ) rad/s. The impedance of the circuit is? A. ( 500 Omega ) B. 1300Omega c. ( 400 Omega ) D. ( 900 Omega ) |
12 |
| 939 | 20 V, 0.1 2 5.90 28. In the circuit of the figure, the source frequency is a = 2000 rad s . The current in the circuit will be (a) 2 A (b) 3.3 A (c) 2/15 A (d) V5 A 5 mH, 412 m 50 uF |
12 |
| 940 | In non-resonant circuit, the nature of circuit for frequencies greater than the resonant frequency is : A . resistive B. capacitive c. inductive D. both 1 and 2 |
12 |
| 941 | A transformer having 4000 turns on its primary side and 500 turns on the secondary side. If the input voltage is ( 240 V, ) find out the output voltage of the secondary side of the transformer? A . ( 15 ~ V ) в. ( 30 V ) c. ( 60 V ) D. ( 120 V ) E . ( 240 mathrm{V} ) |
12 |
| 942 | The voltage across the capacitor as a function of time is given by ( 10^{x} t^{2} V ) then find ( x ) A. 7 B. 6 ( c cdot-5 ) D. 4 |
12 |
| 943 | The number of turns in the coil of an AC generator is 5000 and the area of the coil is0.25 ( m^{2} . ) The coil is rotated at the rate of 100 cycles /sec in the magnetic field of ( 0.2 W / m^{2} . ) then the peak value will be : A. ( 786 mathrm{kv} ) B. 178 kV c. ( 157 mathrm{kv} ) D. 123 kv |
12 |
| 944 | Primary winding and secondary winding of a transformer has 100 and 300 turns respectively. If its input power is ( 60 mathrm{W} ) then output power of the transformer will be A . 240 ( w ) B. 180 ( w ) ( c cdot 60 w ) D. 20 W |
12 |
| 945 | What are the values of the elements? | 12 |
| 946 | An inductor and resistor are connected in series with an ac source. In this circuit. A. The current and the PD across the resistance lead the PD across the inductance B. The current and the PD across the resistance lag behind the PD across the inductance by an angle ( pi / 2 ) C. The current and the PD across the resistance lag behind the PD across the inductance by an angle ( pi ) D. The PD across the resistance lags behind the PD across the inductance by an angle ( pi / 2 ) but the current in resistance leads the PD across the inductance by ( pi / 2 ) |
12 |
| 947 | A coil of inductive reactance ( 1 / sqrt{3} Omega ) and resistance ( 1 Omega ) is connected to ( 200 V, 50 H z ) A.C. supply. The time lag between maximum voltage and current is A ( cdot frac{1}{600} s ) в. ( frac{1}{200} s ) c. ( frac{1}{300} s ) D. ( frac{1}{500} s ) |
12 |
| 948 | A current source sends a current i ( = ) ( i_{0} cos (omega t) . ) When connected across an unknown load gives a voltage output of, ( boldsymbol{v}=boldsymbol{v}_{0} sin (omega t+boldsymbol{pi} / 4) ) across that load Then voltage across the current source may be brought in phase with the current through it by A. connecting an inductor in series with the load B. connecting a capacitor in series with the load C. connecting an inductor in parallel with the load D. connecting a capacitor in parallel with the load. |
12 |
| 949 | In an AC circuit, electrical energy is consumed in A . B. ( c cdot R ) D. Land |
12 |
| 950 | If the frequency of the AC source connected across a series LCR circuit is continuously in which the following is observed. Assume all other parameters are kept the same. A. rms current continously increases. B. rms current remains constant c. rms current first increases, reaches a maximum and then decrease D. rms current first decreases, reached a minimum and then increases |
12 |
| 951 | Draw the graph of ( I_{r m s} rightarrow omega ) for an A.C. L-C-R series circuit and hence explain Q-factor. |
12 |
| 952 | Draw a labelled diagram of a step-up transformer and explain how it works. State two characteristics of the primary coil as compared to its secondary coil. | 12 |
| 953 | The power in series ( R L C ) -circuit with ( A C ) source is given by : A. zero B. ( V I sin phi ) c. ( V I ) D. ( V I cos phi ) |
12 |
| 954 | In an ideal step-up transformer input voltage is ( 110 mathrm{V} ) and current flowing in the secondary is ( 10 mathrm{A} ), if transformation ratio is ( 10, ) calculate output voltage, current in primary input power and output power. |
12 |
| 955 | If the phase difference between Alternating Voltage and Alternating Current is ( frac{pi}{6} ) and the resistance in the circuit is ( sqrt{300} Omega, ) then the impedance of the circuit will be A . 25Omega B. ( 50 Omega ) ( c cdot 20 Omega ) D. ( 100 Omega ) |
12 |
| 956 | A transformer consisting of 300 turns in the primary and 150 turns in the secondary gives output power of ( 2.2 k W ) .f the current in the secondary coil is ( mathbf{1 0} A, ) then the input voltage and current in the primary coil are : A . ( 220 V ) and ( 10 A ) B. ( 440 V ) and ( 5 A ) c. ( 440 V ) and ( 20 A ) D. 220V and 20A |
12 |
| 957 | A ( 50 H z ) alternating current of crest value ( 2.0 . A ) flows through the primary of a transformer. If the mutual inductance between the primary and secondary is ( 0.25 H . ) The crest voltage induced in the secondary is A . ( 50 V ) B. ( 100 V ) c. ( 200 V ) D. 300V |
12 |
| 958 | toppr Q Type your question_ ( A ) B. ( c ) ( D ) |
12 |
| 959 | A coil has an inductance of ( 0.7 ~ H ) and is joined in series with a resistance of 220Omega. When an alternating emf of ( 220 V ) at ( 50 ~ c p s ) is applied to it, then the wattless component of the current in the circuit is (take ( 0.7 pi=2.2) ) ( mathbf{A} cdot 5 A ) B. ( 0.5 A ) ( mathbf{c} cdot 0.7 A ) D. ( 7 A ) |
12 |
| 960 | ( ln ) a ( L C ) circuit. Angular frequency at resonance is ( boldsymbol{w} ). What will be the new angular frequency when inductor’s introduces is made 2 times and capacitance is made 4 times? A ( cdot frac{w}{sqrt{2}} ) в. ( frac{w}{2 sqrt{2}} ) c. ( 2 w ) D. ( frac{2 w}{sqrt{2}} ) |
12 |
| 961 | Determine the voltage across the inductor as a function of time(in ( mathrm{mV} ) ) |
12 |
| 962 | After the capacitor gets fully charged, ( mathbf{S}_{1} ) is opened and ( mathbf{S}_{2} ) is closed so that the inductor is connected in series with the capacitor. Then, A ( . ) at ( t=0, ) energy stored in the circuit is purely in the form of magnetic energy B. at any time ( t>0 ), current in the circuit is in the same c. at ( t>0, ) there is no exchange of energy between the inductor and capacitor D. at any time ( t>0 ), instantaneous current in the circuitt ( operatorname{may} mathrm{v} sqrt{frac{mathrm{c}}{mathrm{L}}} ) |
12 |
| 963 | In series ( L-C-R ) circuit voltage drop across resistance is ( 8 V, ) across inductor is ( 6 V ) and across capacitor is ( mathbf{1 2} V ). Then A. Voltage of the source will be leading in the circuit B. Voltage drop across each element will be less than the applied voltage. c. Power factor of the circuit will be ( 3 / 4 ) D. None of the above |
12 |
| 964 | A step down transformer is used on ( 1000 V ) line to deliver ( 20 A ) at ( 120 V ) at the secondary coil. If the efficiency of the transformer is ( 80 % ) the current drawn from the line is ( mathbf{A} cdot 3 A ) в. 30 А ( mathbf{c} cdot 0.3 A ) D. 2.4 ( A ) |
12 |
| 965 | The inductive reactance of a coil is ( 2500 Omega . ) On increasing it’s selfinductance to three times, the new inductive reactance will be: A. ( 7500 Omega ) B. 2500Omega c. ( 1225 Omega ) D. zero |
12 |
| 966 | For an ideal transformer: A. Output power = Input power B. Efficiency is ( 100 % ) C ( cdot frac{V_{s}}{V_{p}}=frac{I_{p}}{I_{s}} ) D. All of these |
12 |
| 967 | An AC circuit containing ( 80 m H ) inductor and a ( 60 mu F ) capacitor is in series with ( 15 Omega ) resistance. They are connected to ( 230 V, 50 H z ) AC supply What is the total average power absorbed by the circuit? A . zero B. 5 watt c. 40 watt D. 10 watt |
12 |
| 968 | ( ln ) an oscillating ( boldsymbol{L}-boldsymbol{C} ) circuit, the maximum charge on the capacitor is ( Q ) The charge on the capacitor, when the energy is stored equally between the electric and magnetic field is: A ( cdot frac{Q}{2} ) B. ( frac{Q}{sqrt{2}} ) c. ( frac{Q}{sqrt{3}} ) D. ( frac{Q}{3} ) |
12 |
| 969 | If a capacitance ( C ) is connected in series with an inductor of inductance ( L ) then the angular frequency will be A ( cdot sqrt{frac{1}{L C}} ) в. ( sqrt{frac{L}{C}} ) c. LC D. ( sqrt{L C} ) |
12 |
| 970 | 60. In the circuit shown (figure), the coil has inductance and resistance. When X is joined to Y, the time constant is t during the growth of current. When the steady state is reached, heat is produced in the coil at a rate P. X is now joined to Z. After joining X and Z: (a) The total heat produced in the coil is PT (b) The total heat produced in the coil is 1/2 Pt (c) The total heat produced in the coil is 2PT (d) The data given are not sufficient to reach a conclusion |
12 |
| 971 | What are resonating frequency for two circuits. | 12 |
| 972 | The frequency of oscillation of current in the inductance is A ( cdot frac{1}{3 sqrt{L C}} ) в. ( frac{1}{6 pi sqrt{L C}} ) c. ( frac{1}{sqrt{L C}} ) D. ( frac{1}{3 pi sqrt{L C}} ) |
12 |
| 973 | A power (set up) transformer with an 1: 8 turn ratio has ( 60 H_{z}, 120 V ) across the primary, the load in the secondary is ( 10^{4} Omega . ) The current in the secondary is A . ( 96 A ) B. ( 0.96 A ) ( mathbf{c} .9 .6 A ) D. 96 m ( A ) |
12 |
| 974 | A resistor and an inductor are connected to an ac supply of ( 120 mathrm{V} ) and ( mathbf{5 0} boldsymbol{H} z . ) The current in the circuit is ( mathbf{3} boldsymbol{A} ) If the power consumed in the circuit is ( 108 W, ) then the resistance in the circuit is A. ( 12 Omega ) в. ( 40 Omega ) c. ( sqrt{(52 times 28)} ), D. ( 360 Omega ) |
12 |
| 975 | The figure shows the graphical variation of the reactance of a capacitor with frequency of ac source Find the capacitance of the capacitor |
12 |
| 976 | A ( 100 Omega ) resistor is connected to a ( 220 V, 50 H z ) AC supply. Find rms value of current in the circuit and the net power consumed for a complete cycle. A. ( 2.20 A, 484 W ) в. ( 3.20 A, 564 W ) c. ( 1.60 A, 278 W ) D. ( 5.80 A, 646 W ) |
12 |
| 977 | Statement ( (A): ) The reactance offered by an inductance in A.C. circuit decreases with the increase of ( A C ) frequency. Statement ( (mathrm{B}): ) The reactance offered by a capacitor in AC circuit increases with the increase of AC frequency. A. A is true but B is false B. Both A and B are true c. A is false but B is true D. Both A and B are false |
12 |
| 978 | A capacitor of capacitance ( C ) has initial charge ( Q_{0} ) is connected to a inductor of inductance L as shown. Att = 0 switch S is closed. Then the current though the inductor when energy in the capacitor is three times energy of inductor is A ( cdot frac{Q_{0}}{2 sqrt{L C}} ) B. ( frac{Q_{0}}{sqrt{L C}} ) c. ( frac{2 Q_{0}}{sqrt{L C}} ) D. ( frac{Q_{0}}{4 sqrt{L C}} ) |
12 |
| 979 | C ome 5 5. In an LCR circuit, the capacitance is changed from to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to (a) 4L (b) 2L (c) L/2 (d) L/4 (AIEEE 2004) |
12 |
| 980 | In a series LCR circuit,the inductive reactance is twice the resistance and the capacitance reactance is ( frac{1}{3}^{r d} ) the inductive reactance. The power factor of the circuit is: A . 0.5 B. 0.6 ( c .0 .8 ) D. |
12 |
| 981 | In the following diagram, the value of emf of A.C. source will be : A . ( 40 V ) B . ( 40 sqrt{2} V ) c. ( frac{40}{sqrt{2}} V ) D. ( 160 V ) |
12 |
| 982 | Draw a labelled diagram of a step-up transformer. Obtain the ratio of secondary to primary voltage in terms of number of terns and current in the two coil. |
12 |
| 983 | A ( 100 Omega ) resistor is connected to a ( 220 V, 50 H z A C ) supply. Find ( r m s ) value of current in the circuit : A . ( 1.10 A ) в. ( 2.20 A ) c. ( 3.30 A ) D. ( 4.40 A ) |
12 |
| 984 | An ideal coil of ( 10 mathrm{H} ) is joined in series with a resistance of ( 5 Omega & ) a battery of ( 5 V . ) Two seconds after the connection is made, the current flowing in amperes in the circuit is: A ( cdot e^{-1} ) В ( cdotleft(1-e^{-1}right) ) ( mathbf{c} cdot 1-e ) D. ( e ) |
12 |
| 985 | Assertion The only element that dissipates energy in an ac circuit is the resistive element Reason There are no power losses associated |
12 |
| 986 | Power dissipated in pure inductance will be ( ^{A} cdot frac{L I^{2}}{2} ) В ( cdot 2 L I^{2} ) c. ( frac{L I^{2}}{4} ) D. zero |
12 |
| 987 | The current in the shown circuit is found to be ( 4 sin left(314 t-frac{pi}{4}right) A . ) Find the value of inductance | 12 |
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