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This mock test of Test: Alternating Current (Competition Level 1) for Class 12 helps you for every Class 12 entrance exam.
This contains 30 Multiple Choice Questions for Class 12 Test: Alternating Current (Competition Level 1) (mcq) to study with solutions a complete question bank.
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QUESTION: 1

In an ac circuit, peak value of voltage is 423 volts. Its effective voltage is

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QUESTION: 2

An ac circuit, the current is given by i = 4 sin (100pt + 30º) ampere. The current becomes maximum first time (after t = 0) at t equal to

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QUESTION: 3

The instantaneous value of current in an ac circuit is I = 2 sin (100pt + p/3) A. The current at the beginning (t = 0) will be

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QUESTION: 4

If instantaneous value of current is I = 10 sin (314 t) A, then the average current for the half cycle will be

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QUESTION: 5

In a circuit an a.c. current and a d, c. current are supplied together. The expression of the instantaneous current is given as i = 3 + 6 sin wt. Then the rms value of the current is

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QUESTION: 6

The emf and the current in a circuit are E = 12 sin (100pt) ; I = 4 sin (100pt + p / 3) then

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QUESTION: 7

If the frequency of alternating potential is 50Hz then the direction of potential, changes in one second by

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QUESTION: 8

The value of alternating e.m.f. is e = 500 sin 100pt , then the frequency of this potential in Hz is

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QUESTION: 9

The domestic power supply is at 220 volt. The amplitude of emf will be

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QUESTION: 10

The average value or alternating current for half cycle in terms of I_{0} is

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QUESTION: 11

Sinusoidal peak potential is 200 volt with frequency 50Hz. It is represented by the equation

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QUESTION: 12

RMS value of ac i = i_{1} cos wt + i_{2} sin wt will be

Solution:

I=(I1)cosωt+(I_{2})sinωt

(I^{2})_{mean}=I_{1}^{2}cos^{2}ωt+I_{2}^{2}sin^{2}ωt+I_{1}I_{2}cosωtsinωt

I_{1}^{2}×(1/2)×i_{2}^{2}×(1/2)+2_{I}1I_{2}×0

I_{rms}=√(i^{2})_{mean}=√(I_{1}^{2}+I_{2}^{2}/2)=(1/√2)( I_{1}^{2}+I_{2}^{2})^{1/2}

QUESTION: 13

The phase difference between the alternating current and voltage represented by the following equation I = I_{0} sin wt, E = E_{0} cos (wt + p / 3), will be

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QUESTION: 14

The inductive reactance of a coil is 1000W. If its self inductance and frequency both are increased two times then inductive reactance will be

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QUESTION: 15

In an L.C.R series circuit R = 1W, X_{L} = 1000W and X_{C} = 1000W. A source of 100 m.volt is connected in the circuit the current in the circuit is

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QUESTION: 16

A coil of inductance 0.1 H is connected to an alternating voltage generator of voltage E = 100 sin (100t) volt. The current flowing through the coil will be

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QUESTION: 17

Alternating current lead the applied e.m.f. by p/2 when the circuit consists of

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QUESTION: 18

A coil has reactance of 100W when frequency is 50Hz. If the frequency becomes 150Hz, then the reactance will be

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QUESTION: 19

A resistance of 50W, an inductance of 20/p henry and a capacitor of 5/p mF are connected in series with an A.C. source of 230 volt and 50Hz. The impedance of circuit is

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QUESTION: 20

The potential difference between the ends of a resistance R is V_{R} between the ends of capacitor is V_{C} = 2V_{R} and between the ends of inductance is V_{L} = 3V_{R}, then the alternating potential of the source in terms of V_{R} will be

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QUESTION: 21

The percentage increase in the impedance of an ac circuit, when its power factor changes form 0.866 to 0.5 is (Resistance constant)

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QUESTION: 22

In a series resonant L^{_}C^{_}R circuit, if L is increased by 25% and C is decreased by 20%, then the resonant frequency will

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QUESTION: 23

Which of the following statements is correct for L^{_}C^{_}R series combination in the condition of resonance

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QUESTION: 24

An ac circuit resonates at a frequency of 10 kHz. If its frequency is increased to 11 kHz, then

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QUESTION: 25

In an ac circuit emf and current are E = 5 cos wt volt and I = 2 sin wt ampere respectively. The average power dissipated in this circuit will be

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QUESTION: 26

A choke coil of negligible resistance carries 5 mA current when it is operated at 220 V. The loss of power in the choke coil is –

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QUESTION: 27

In an A.C. circuit, a resistance of 3W, an inductance coil of 4W and a condenser of 8W are connected in series with an A.C. source of 50 volt (R.M.S.). The average power loss in the circuit will be

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QUESTION: 28

Two bulbs of 500 watt and 300 watt work on 200 volt r.m.s. the ratio of their resistances will be –

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QUESTION: 29

Three bulbs of 40, 60 and 100 watt are connected in series with the source of 200 volt. Then which of the bulb will be glowing the most –

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QUESTION: 30

Alternating current can not be measured by direct current meters, because –

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### Test B - Alternating Current (AC) Assignment

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### Test D - Alternating Current (AC) Assignment

Doc | 1 Page

### Test C - Alternating Current (AC) Assignment

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