# MCQs For NCERT Class 12 Physics Chapter 7 Alternating Induction

Please refer to the MCQ Questions for Class 12 Physics Chapter 7 Alternating Induction with Answers. The following Alternating Induction Class 12 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 12. Our experts have designed MCQ Questions for Class 12 Physics with Answers for all chapters in your NCERT Class 12 Physics book.

## Alternating Induction Class 12 MCQ Questions with Answers

See below Alternating Induction Class 12 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. A circuit when connected to an AC source of 12 V gives a current of 0.2 A. The same circuit when connected to a DC source of 12 V, gives a current of 0.4 A. The circuit is
(a) series LR
(b) series RC
(c) series LC
(d) series LCR

A

Question. An A.C. circuit containing only capacitance, the current :
(a) lags the voltage by 90°
(b) leads the voltage by 90°
(c) remains in phase with voltage
(d) leads the voltage in 180°

B

Question. A choke coil has:
(a) Low inductance and low resistance
(b) High inductance and high resistance
(c) Low inductance and high resistance
(d) High inductance and low resistance

D

Question. The potential differences across the resistance,capacitance and inductance are 80 V, 40 V and 100 V respectively in an L-C-R circuit. The power factor of this circuit is
(a) 0.4
(b) 0.5
(c) 0.8
(d) 1.0

C

Question. In an electrical circuit R, L, C and ac voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the current in the circuit is p/3. If instead, C is removed from the circuit, the phase difference is again p/3. The power factor of the circuit is
(a) 1/2
(b) 1/√2
(c) 1
(d) √3/2

C

Question. Turn ratio in a step up transformer is 1 : 2 if a Lechlanche cell of 1.5 V is connected across the input, then the voltage across the output will be
(a) 0.1 V
(b) 1.5 V
(c) 0.75 V
(d) zero

D

Question. In the circuit shown below what will be the reading of the voltmeter and ammeter ?
(Total impedance of circuit Z = 100W)
(a) 200 V, 1A
(b) 800 V, 2A
(c) 100 V, 2A
(d) 220 V, 2.2 A

D

Question. A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when
(a) a capacitance of reactance XC = XL is included in the same circuit.
(b) an iron rod is inserted in the coil.
(c) frequency of the AC source is decreased.
(d) number of turns in the coil is reduced.

B

Question. In a circuit the coil of a choke :
(a) decreases the current
(b) increases the current
(c) has high resistance to D. C. circuit
(d) no effect with the current

A

Question. In a circuit, the current lags behind the voltage by a phase difference of p /2, the circuit will contain which of the following :
(a) only R
(b) only C
(c) R and C
(d) only L

D

Question. An inductor 20 mH, a capacitor 50 mF and a resistor 40 W are connected in series across a source of emf V = 10 sin 340t. The power loss in A.C. circuit is
(a) 0.76 W
(b) 0.89 W
(c) 0.51 W
(d) 0.67 W

C

Question. The coefficient of mutual inductance, when magnetic flux changes by 2 × 10–2 Wb and current changes by 0.01 A is
(a) 8 henry
(b) 4 henry
(c) 3 henry
(d) 2 henry

D

Question. 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

D

Question. A capacitor of capacitance 2μF 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 m A, the voltage across the capacitor will be :
(a) 0.16 V
(b) 0.32 V
(c) 79.5 V
(d) 159 V

A

Question. A 50 Hz a.c. source of 20 volt is connected across R and C as shown in figure. The voltage across R is 12 volt. The voltage across C is :
(a) 8 V
(b) 16 V
(c) 10 V
(d) not possible to determine unless values of R and C are given

B

Question. 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 of the source is
(a) 20.0 V
(b) 25.6 V
(c) 31.9 V
(d) 53.5 V

B

Question. With the decrease of current in the primary coil from 2 amperes to zero value in 0.01s the emf generated in the secondary coil is 1000 volts.
The mutual inductance of the two coils is
(a) 1.25 H
(b) 2.50 H
(c) 5.00 H
(d) 10.00 H

C

Question. An AC source of angular frequency w 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 w/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 w
(a) √3/5
(b) √2/5
(c) √1/5
(d) √4/5

A

Question. If an AC main supply is given to be 220 V. The average emf during a positive half cycle will be
(a) 198 V
(b) 220 V
(c) 240 V
(d) 220 2V

A

Question. A small signal voltage V(t) = V0 sinwt is applied across an ideal capacitor
(a) Current I(t) is in phase with voltage V(t).
(b) Current I(t) leads voltage V(t) by 180°.
(c) Current I(t), lags voltage V(t) by 90°.
(d) Over a full cycle the capacitor C does not consume any energy from the voltage source.

C,D

Question. A coil has an inductance of 0.7 henry and is joined in series with a resistance of 220 W. When the alternating emf of 220 V at 50 Hz is applied to it then the phase through which current lags behind the applied emf and the wattless component of current in the circuit will be respectively
(a) 30°, 1 A
(b) 45°, 0.5 A
(c) 60°, 1.5 A
(d) none of these

B

Question. An inductor and a resistor in series are connected to an A.C. supply of variable frequency. As the frequency of the source is increased, the phase angle between current and the potential difference across L will:
(a) first increase and then decrease
(b) first decrease and then increase
(c) go on decreasing
(d) go on increasing

D

Question. In a AC circuit the voltage and current are described by V 200sin (319t -π/6) volts and i 50sin (314t + π/6)ma respectively. The average power dissipated in the circuit is :
(a) 2.5 watts
(b) 5.0 watts
(c) 10.0 watts
(d) 50.0 watts

A

Question. A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be
(a) 2.0 A
(b) 4.0 A
(c) 8.0 A
(d) 20/√13 A

B

Question. What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10 mF and w = 1000 s–1?
(a) 1 mH
(b) cannot be calculated unless R is known
(c) 10 mH
(d) 100 mH

D

Question. If we decrease the frequency of the applied A.C. with a purely capacitive load, do (1) the amplitude of Vc and (2) amplitude of Ic increase, decrease of remain the same.
(a) (1) increase (2) same
(b) (1) same (2) increase
(c) (1) same (2) decrease
(d) (1) decrease (2) same

C

Question. In an ac circuit an alternating voltage 200 2 sin100 t volts is connected to a capacitor of capacity 1 mF. The r.m.s. value of the current in the circuit is
(a) 10 mA
(b) 100 mA
(c) 200 mA
(d) 20 mA

D

Question. A capacitor of capacity C has reactance X.
If capacitance and frequency become double then reactance will be
(a) 4X
(b) X/2
(c) X/4
(d) 2X

C

Question. An inductor coil of inductance L is cut into two equal parts and both the parts are connected in parallel. The net inductance is :
(a) L
(b) L/2
(c) L/4
(d) 2 L.

C

Question. A series R-C circuit is connected to an alternating voltage source. Consider two situations :
(i) When capacitor is air filled.
(ii) When capacitor is mica filled.
Current through resistor is i and voltage across capacitor is V then
(a) ia > ib
(b) Va = Vb
(c) Va < Vb
(d) Va > Vb

D

Question. In the given circuit the reading of voltmeter V1 and V2 are 300 volts each. The reading of the voltmeter V3 and ammeter A are respectively
(a) 150 V, 2.2 A
(b) 220 V, 2.2 A
(c) 220 V, 2.0 A
(d) 100 V, 2.0 A

B

Question. A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is p/3.
If instead C is removed from the circuit, the phase difference is again p/3 between current and voltage.
The power factor of the circuit is
(a) zero
(b) 0.5
(c) 1.0
(d) –1.0

C

Question. The current in resistance R at resonance is C
(a) zero
(b) minimum but finite
(c) maximum but finite
(d) infinite

Question. An inductance L having a resistance R is connected to an alternating source of angular frequency w. The Quality factor Q of inductance is
(a) R/ wL
(b) (wL/R)2
(c) (R /wL)1/2
(d) wL/R

D

Question. In an A.C. circuit, the current flowing in inductance is I = 5 sin (100 t – p/2) amperes and the potential difference is V = 200 sin (100 t) volts. The power consumption is equal to
(a) 1000 watt
(b) 40 watt
(c) 20 watt
(d) zero

D

Question. Two cables of copper are of equal lengths. One of them has a single wire of area of cross-section A, while other has 10 wires of cross-sectional area A/10 each. Give their suitability for transporting A.C. and D.C.
(a) only multiple strands for A.C., either for D.C.
(b) only multiple strands for A.C., only single strand for D.C.
(c) only single strand for D.C., either for A.C.
(d) only single strand for A.C., either for D.C.

A

Question. For the circuit shown in the fig., the current through the inductor is 0.9 A while the current through the condenser is 0.4 A. Then
(a) current drawn from generator I = 1.13 A
(b) w = 1/(1.5 L C)
(c) I = 0.5 A
(d) I = 0.6 A

C

Question. An ac voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3 W, the phase difference between the applied voltage and the current in the circuit is
(a) p/6
(b) p/4
(c) p/2
(d) zero

B

Question. L, C, R represent physical quantities inductance,capacitance and resistance respectively. The combinations which have the dimensions of frequency are
(a) 1/RC (b) R/L
(c) 1/ LC (d) C/L

C

Question. An inductance L having a resistance R is connected to an alternating source of angular frequency w. The Quality factor Q of inductance is
(a) R/ wL
(b) (wL/R)2
(c) (R /wL)½
(d) wL/R

D

Question. The value of quality factor is A,
(a) ωL /R
(b) 1/ωRC
(c) √LC
(d) L/R

B

Question. An inductor 20 mH, a capacitor 100 mF and a resistor 50 W are connected in series across a source of emf, V = 10 sin 314t. The power loss in the circuit is
(a) 0.79 W
(b) 0.43 W
(c) 2.74 W
(d) 1.13 W

A

Question. 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 the primary coil will be
(a) 1600 amp
(b) 20 amp
(c) 4 amp
(d) 1.5 amp

C

Question. The mutual inductance of a pair of coils, each of N turns, is M henry. If a current of I ampere in one of the coils is brought to zero in t second, the emf induced per turn in the other coil, in volt, will be
(a) MI /t
(b) NMI/t
(c) MN /It
(d) MI/Nt

A

Question. An series L-C-R circuit is connected to a source of A.C. current. At resonance, the phase difference between the applied voltage and the current in the circuit, is
(a) p
(b) zero
(c) p/4
(d) p/2

B

Question. The tuning circuit of a radio receiver has a resistance of 50W, an inductor of 10 mH and a variable capacitor. A 1 MHz radio wave produces a potential difference of 0.1 mV. The values of the capacitor to produce resonance is (Take p2 = 10)
(a) 2.5 pF
(b) 5.0 pF
(c) 25 pF
(d) 50 pF

A

Question. A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an acsource, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be
(a) 4.0 A
(b) 8.0 A
(c) 20 /√13 .A
(d) 2.0 A

A

Question. An ideal coil of 10H is connected in series with a resistance of 5W and a battery of 5V. After 2 sec the connection is made, the current flowing in ampere in the circuit is
(a) (1 – e–1)
(b) (1 – e)
(c) e
(d) e–1

A

Question. 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

C

Question. In an A.C. circuit, Irms and I0 are related as
(a) Irms = pI0
(b) Irms = 2 I0
(c) Irms = I0/p
(d) Irms = I0 / 2

D

Question. A 40 mF capacitor is connected to a 200 V, 50 Hz ac supply. The r.m.s value of the current in the circuit is, nearly
(a) 1.7 A
(b) 2.05 A
(c) 2.5 A
(d) 25.1 A