Alternating Current PYQs Set 2 (PDF)

Set 2 of 9 · Questions 31-60 of 244

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Mere Teacher · Previous Year Questions NEET Physics · Alternating Current · Set 2 (Q31-60)
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31. $A inductor 20 mH a capacitor 100 µF and a resistor 50 Ω are connected in series across a source of emf, V = 10 sin 314 t. The power loss in the circuit is:$ (1) $0.79 W$ (2) $1.13 W$ (3) $2.74 W$ (4) $0.43 W$ 32. $A coil has inductance of 0.4 H and resistance of 8Ω . It is connected to an AC source with peak emf 4 V and frequency \frac{30}{π} Hz . The average power dissipated in the circuit is$ (1) $1 W$ (2) $0.5 W$ (3) $0.3 W$ (4) $0.1 W$ 33. $Given below are two statements: Statement I: When the frequency of an AC source in a series LCR circuit increases, the current in the circuit first increases, attains a maximum value and then decreases. Statement II: In a series LCR circuit, the value of power factor at resonance is one. In the light of given statements, choose the most appropriate answer from the options given below.$ (1) $Statement I is incorrect but Statement II is true$ (2) $Both Statement I and Statement II are false$ (3) $Both Statement I and Statement II are true$ (4) $Statement I is correct but Statement II is false$ 34. $In a series LCR circuit R = 200 Ω and the voltage and the frequency of the main supply is 220 V and 50 Hz respectively. On taking out the capacitance from the circuit the current lags behind the voltage by 30 ° . On taking out the inductor from the circuit the current leads the voltage by 30 ° . The power dissipated in the LCR circuit is$ (1) $305 W$ (2) $210 W$ (3) $Zero W$ (4) $242 W$ 35. $In which of the following devices, the eddy current effect is not used?$ (1) $electric heater$ (2) $induction furnace$ (3) $magnetic braking in train$ (4) $electromagnet$ 36. $A transformer is used to light 100 W - 110 V lamp from 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is$ (1) $95 %$ (2) $99 %$ (3) $90 %$ (4) $96 %$ 37. $Which of the following represents the variation of inductive reactance (X_{L}) with the frequency of voltage source (v) ?$ (1) (2) (3) (4) 38. $A series AC circuit containing an inductor (20 mH), a capacitor (120 μ F) and a resistor (60Ω) is driven by an AC source of \frac{24 V}{50 Hz} . The energy dissipated in the circuit in 60 s is:$ (1) $3.39 \times 10^{3} J$ (2) $5.65 \times 10^{2} J$ (3) $5.17 \times 10^{2} J$ (4) $2.26 \times 10^{3} J$ 39. $An AC voltage V = 20 sin 200 πt is applied to a series LCR circuit which drives a current I = 10 sin (200 πt + \frac{π}{3}) . The average power dissipated is:$ (1) $21.6 W$ (2) $200 W$ (3) $173.2 W$ (4) $50 W$ 40. $A series LCR circuit is connected to an alternating source of emf E. The current amplitude at resonant frequency is I_{0} . If the value of resistance R becomes twice of its initial value then amplitude of current at resonance will be$ (1) $2 I_{0}$ (2) $I_{0}$ (3) $\frac{I _{0}}{2}$ (4) $\frac{I _{0}}{2}$ 41. $A fully charged capacitor ' C' with initial charge ' Q_{0}' is connected to a coil of self inductance ' L' at t = 0 . The time at which the energy is stored equally between the electricity and the magnetic field is$ (1) $π LC$ (2) $2 π LC$ (3) $\frac{π}{4} LC$ (4) $LC$ 42. $An alternating current is given by I = I_{A} sin ωt + I_{B} cos ωt . The r.m.s current will be$ (1) $\frac{( I _{A} + I _{B} )}{2}$ (2) $\frac{I _{A}^{2} + I _{B}^{2}}{2}$ (3) $I_{A}^{2} + I_{B}^{2}$ (4) $\frac{I _{A}^{2} + I _{B}^{2}}{2}$ 43. $The average power dissipated in a pure inductor is$ (1) $V I^{2}$ (2) $zero$ (3) $\frac{1}{2} VI$ (4) $\frac{V I ^{2}}{4}$ 44. $Why 220 V AC is more dangerous than 220 V DC?$ (1) $The DC attracts$ (2) $Peak voltage for AC is much larger$ (3) $The body offers less resistance to AC$ (4) $Due to some other reason$ 45. $A capacitor of capacitance 10 μF is connected to an AC source and an AC ammeter. If the source voltage varies as V = 502 sin 100 t, the reading of the am meter is$ (1) $50 mA$ (2) $70.7 mA$ (3) $5.0 mA$ (4) $7.07 mA$ 46. $An inductor 20 mH, a capacitor 50 μF and a resistor 40Ω are connected in series across a source of emf V = 10 sin 340 t . The power loss in AC circuit is [NEET 2016]$ (1) $0.67 W$ (2) $0.76 W$ (3) $0.89 W$ (4) $0.51 W$ 47. $The rms value of conduction current in a parallel plate capacitor is 6.9 μ A. The capacity of this capacitor, if it is connected to 230 V ac supply with an angular frequency of 600 rad/s, will be:$ (1) $5 pF$ (2) $50 pF$ (3) $100pF$ (4) $200pF$ 48. $A capacitor, an inductor and an electric bulb are connected in series to an a.c. supply of variable frequency. As the frequency of the supply is increased gradually, then the electric bulb is found to$ (1) $increase in brightness$ (2) $decrease in brightness$ (3) $increase, reach a maximum and then decrease in brightness.$ (4) $show no change in brightness.$ 49. $Assertion: It is more difficult to move a magnet into a coil with more loops. Reason: This is because emf induced in each current loop resists the motion of the magnet.$ (1) $Both A and R are true and R is a correct explanation for A .$ (2) $Both A and R are true but R is not a correct explanation for A .$ (3) $A is true and R is false.$ (4) $A is false, R is true.$ 50. $A series LCR circuit is subjected to an ac signal of 200 V, 50 Hz . If the voltage across the inductor (L = 10 mH) is 31.4 V, then the current in this circuit is$ (1) $68 A$ (2) $63 A$ (3) $10 A$ (4) $10 mA$ 51. $Primary side of a transformer is connected to 230 V, 50 Hz supply. Turns ratio of primary to secondary winding is 10 : 1 . Load resistance connected to secondary side is 46Ω . The power consumed in it is :$ (1) $12.5 W$ (2) $10.0 W$ (3) $11.5 W$ (4) $12.0 W$ 52. $A series LCR circuit has L = 0.01 H, R = 10 Ω and C = 1 μ F and it is connected to ac voltage of amplitude (V_{m}) 50 V. At frequency 60% lower than resonant frequency, the amplitude of current will be approximately:$ (1) $466mA$ (2) $312mA$ (3) $238mA$ (4) $196mA$ 53. $The LC parallel resonant circuit$ (1) $has a very high impedance$ (2) $has a very high current$ (3) $acts as resistance of very low value$ (4) $has zero impedance$ 54. $The instantaneous values of alternating current and voltages in a circuit are given as i = \frac{1}{2} sin (100 πt) ampe r e = \frac{1}{2} sin (100 πt + π /3) Vol t The average power in Watts consumed in the circuit is:$ (1) $\frac{1}{4}$ (2) $\frac{3}{4}$ (3) $\frac{1}{2}$ (4) $\frac{1}{8}$ 55. $A circuit connected to an ac source of emf e_{0} sin (100 t) with t in seconds, gives a phase difference of \frac{π}{4} between the emf e and current i . Which of the following circuits will exhibit this?$ (1) $RL circuit with R = 1 kΩ and L = 10 mH$ (2) $RL circuit with R = 1 kΩ and L = 1 mH$ (3) $RC circuit with R = 1 kΩ and C = 1 μF$ (4) $RC circuit with R = 1 kΩand C = 10 μF$ 56. $A multimeter reads a voltage of a certain A.C. source as 100 V . What is the peak value of voltage of A.C. source?$ (1) $141.4 V$ (2) $200 V$ (3) $400 V$ (4) $100 V$ 57. $An e.m.f. E = 4 cos (1000 t) volt is applied to an LR circuit of inductance 3 mH and resistance 4Ω . The maximum current in the circuit is$ (1) $\frac{4}{7} A$ (2) $1.0 A$ (3) $\frac{4}{7} A$ (4) $0.8 A$ 58. $The average power dissipated in A.C. circuit is 2 watt. If a current flowing through a circuit is 2 A and impedance is 1Ω, what is the power factor of the A.C. circuit?$ (1) $0$ (2) $0.5$ (3) $\frac{1}{2}$ (4) $1$ 59. $For a series LCR circuit at resonance, the statement which is not true is$ (1) $wattless current is zero$ (2) $power factor is zero$ (3) $peak energy stored by a capacitor = peak energy stored by an inductor$ (4) $average power = apparent power$ 60. $A 100Ω resistance and a capacitor of 100Ω reactance are connected in series across a 220 V source. When the capacitor is 50 % charged, the peak value of the displacement current is [NEET 2016]$ (1) $2.2 A$ (2) $11 A$ (3) $4.4 A$ (4) $112 A$