R4RIN – MCQs, Mock Tests | NCERT Class 12 MCQ Questions for Class 12 Physics Chapter 7 Alternating Current

Power factor of an ac circuit is a measure of:

1. virtual power
2. power lost in the circuit
3. mean power
4. All the above

✅ Correct Answer: 2

The dimensional formula of L/R is similar to that of:

1. requency
2. time
3. length
4. None of the above

✅ Correct Answer: 2

Which of the following has dimensions different from the rest?

1. L/R
2. 1RC
3. LC−−−√
4. RC

✅ Correct Answer: 2

The dimensional formula of impedance is;

1. [ML2T-2A-2]
2. ML2T-3A-2]
3. [ML2T-2A-1]
4. [ML2T-2A-3]

✅ Correct Answer: 2

Energy dissipates in LCR circuit in :

1. L only
2. C only
3. R only
4. All the above

✅ Correct Answer: 3

An iron core transformer with a turns ratio of 8 : 1 has 120 V applied across the primary. The voltage across the

1. 15 V
2. 120 V
3. 180
4. 960 V

✅ Correct Answer: 1

What is the ratio of inductive and capacitance reactances in an ac circuit?

1. 1
2. ω²L
3. ω²LC
4. l

✅ Correct Answer: 3

An acceptor circuit is :

1. series resonant circuit
2. parallel resonant circuit
3. LCR circuit
4. None of these

✅ Correct Answer: 1

A broadcast circute broadcasts at 300 m band. A condenser of capacitance 2.4 lµF is available. The value of the inductance required for resonant circuit is:

1. 10-4 H
2. 10-8 H
3. 10-6 H
4. 10-2 H

✅ Correct Answer: 2

In series resonant circuit:

1. reactance is zero
2. current is zero
3. voltage is zero
4. None of the above

✅ Correct Answer: 4

In series resonant circuit:

1. reactance is zero
2. current is zero
3. voltage is zero
4. None of the above

✅ Correct Answer: 4

In series resonant circuit:

1. reactance is zero
2. current is zero
3. voltage is zero
4. None of the above

✅ Correct Answer: 4

The no. of turns in the primary coil of a transformer is 200 and the no. of turns in the secondary is 10. If 240 V a.c. is applied to primary, the output from the secondary

1. 6 V
2. 12 V
3. 24 V
4. 48 V

✅ Correct Answer: 2

The no. of turns in the primary coil of a transformer is 200 and the no. of turns in the secondary is 10. If 240 V a.c. is applied to primary, the output from the secondary

1. 6 V
2. 12 V
3. 24 V
4. 48 V

✅ Correct Answer: 2

The no. of turns in the primary coil of a transformer is 200 and the no. of turns in the secondary is 10. If 240 V a.c. is applied to primary, the output from the secondary

1. 6 V
2. 12 V
3. 24 V
4. 48 V

✅ Correct Answer: 2

Transformer works on the principle of:

1. convertor
2. invertor
3. mutual induction
4. self-induction

✅ Correct Answer: 3

Which of the following effects is not shown in alternating current ?

1. Chemical effect
2. Magnetic effect
3. Heating current
4. All the above

✅ Correct Answer: 1

An ac ammeter connected in series in an ac circuit reads 5A. The peak value of current:

1. 5 A (b) (c)
2. 5√2A
3. 5√5 A
4. Zero

✅ Correct Answer: 2

The phase difference b/w the A.C. and e.m.f. π2 Which of the following can not be the instituent of the circuit?

1. LC
2. L alone
3. C alone
4. RL

✅ Correct Answer: 4

Faraday constant:

1. depends on the amount of the electrolyte
2. depends on the current in the electrolyte
3. is a universal constant
4. depends on the amount of charge passed through the electrolyte

✅ Correct Answer: 3

A rejector circuit is:

1. series resonant circuit
2. parallel resonant circuit
3. LCR circuit
4. None of the above

✅ Correct Answer: 2

In pure inductive circuit current

1. lags behind emf by π/2
2. leads the emf by π/2
3. lags behind emf by π
4. leads the emf by π

✅ Correct Answer: 1

The current through an inductor of 1H is given by I = 3t sin t. The voltage across the inductor of 1 H is:

1. 3 sin t + 3 cos t
2. 3 sin t + 3t cos t
3. 3 cos t + t sin t
4. 3t cos t + sin t

✅ Correct Answer: 2

Two coils X and Y are connected in series across a 240 V, 50 Hz supply. The resistance of X is 5Ω and inductance of Y is 0.02 H. The power consumed is 3 kW and the power factor is 0.75. The impedance of the circuit is:

1. 0.144 Ω
2. 1.44
3. 14.4 Ω
4. 144 Ω

✅ Correct Answer: 3

In the above problem, the value of the resistance of the coil Y is:

1. 0.58 Ω
2. 5.8 Ω
3. 1.16
4. 11.6 Ω

✅ Correct Answer: 2

An electric circuit containing capacitor only suffers:

1. equal resistance for A.C. and D.C. (b)
2. Resistance of A.C. > Resistance of D.C.
3. Resistance for A.C. < Resistance of D.C.
4. offers infinite resistance for D.C.

✅ Correct Answer: 4

The average power dissipation in pure inductance or capacitance is: (a) 12 LI²

1. 12 LI²
2. 3/2 CV²
3. either (a) or (b)
4. zero

✅ Correct Answer: 4