# Alternating Current MCQ Class 12 Physics

Please refer to Chapter 7 Alternating Current MCQ Class 12 Physics with answers below. These multiple-choice questions have been prepared based on the latest NCERT book for Class 12 Physics. Students should refer to MCQ Questions for Class 12 Physics with Answers to score more marks in Grade 12 Physics exams. Students should read the chapter Alternating Current and then attempt the following objective questions.

## MCQ Questions Class 12 Physics Chapter 7 Alternating Current

The Alternating Current MCQ Class 12 Physics provided below covers all important topics given in this chapter. These MCQs will help you to properly prepare for exams.

Question. In a pure capacitive circuit if the frequency of ac source is doubled, then its capacitive reactance will be
(a) remains same
(b) doubled
(c) halved
(d) zero

C

Question. What is the reciprocal of impedance?
(b) Inductance
(c) Reactance
(d) Conductance

A

Question. In which of the following circuits the maximum power dissipation is observed?
(a) Pure capacitive circuit
(b) Pure inductive circuit
(c) Pure resistive circuit
(d) None of these

C

Question. Quality factor and power factor both have the dimensions of
(a) time
(b) frequency
(c) work
(d) angle

D

Question. The reciprocal of impedance is called
(a) reactance.
(c) inductance.
(d) conductance.

D

Question. The frequency of A.C. mains in India is
(a) 30 c/s
(b) 50 c/s
(c) 60 c/s
(d) 120 c/s

B

Question. What is the peak value of the voltage of an electric lamp connected to a 220 V, 50 Hz supply?
(a) 311 V
(b) 320 V
(c) 211 V
(d) 210 V

A

Question. Energy dissipates in LCR circuit in :
(a) L only
(b) C only
(c) R only
(d) All of the above

C

Question. Alternating currents can be produced by a
(a) dynamo
(b) choke coil
(c) transformer
(d) electric motor

A

Question. An A.C. source is connected to a resistive circuit. Which of the following is true?
(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.

C

Question. The dimensional formula of L/R is similar to that of:
(a) frequency
(b) time
(c) length
(d) none of these

B

Question. The dimensions of Inductance/Resistance is same as the dimension of
(a) time
(b) capacitance
(c) capacitive reactance
(d) inductive reactane

A

Question. A capacitor acts as an infinite resistance for
(a) DC
(b) AC
(c) DC as well as AC
(d) neither AC nor DC

A

Question. In which of the following circuits the maximum power dissipation is observed?
(a) Pure capacitive circuit
(b) Pure inductive circuit
(c) Pure resistive circuit
(d) None of these

C

Question. A capacitor has capacitance C and 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 LCR series circuit, connected to a source E, is at resonance. Then the voltage across
(a) R is zero
(b) R equals applied voltage
(c) C is zero
(d) L equals applied voltage

B

Question. A.C. power is transmitted from a power house at a high voltage as
(a) the rate of transmission is faster at high voltages
(b) it is more economical due to less power loss
(c) power cannot be transmitted at low voltages
(d) a precaution against theft of transmission lines

B

Question. 60 microfarad capacitor is connected to a 110 V, 60 Hz AC supply. What is the value of root mean square value of current in the circuit?
(a) 1.49 ampere
(b) 2.49 ampere
(c) 3.62 ampere
(d) 4.12 ampere

B

Question. The dimensions of Inductance/Resistance is same as the dimension of
(a) time
(b) capacitance
(c) capacitive reactance
(d) inductive reactance

A

Question. Current in a circuit is wattless if
(a) inductance in the circuit is zero
(b) resistance in the circuit is zero
(c) current is alternating
(d) resistance and inductance both are zero

B

Question. Reciprocal of impedance is
(a) susceptance
(b) conductance
(d) transconductance

C

Question. A capacitor in an ideal LC circuit is fully charged by a DC source, then it is disconnected from DC source, the current in the circuit
(a) becomes zero instantaneously
(b) grows , monotonically
(c) decays monotonically
(d) oscillate infinitely

A

Question. Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is incorrect?
(a) For a given power level, there is a lower current.
(b) Lower current implies less power loss.
(c) Transmission lines can be made thinner.
(d) It is easy to reduce the voltage at the receiving end using step-down transformers.

C

Question. The opposition offered by ohmic and non ohmic components is
(a) inductive reactance
(b) capacitive reactance
(c) impedance
(d) all of these

C

Question. A transformer is an electrical device used for
(a) Producing direct current
(b) Producing alternating current
(c) Changing D.C into A.C.
(d) Changing A.C. voltages

C

Question. A resistance R Ω is connected in series with capacitance C Farad value of impedance of the circuit is 10 Ω and R = 6Ω so, find the power factor of circuit.
(a) 0.4
(b) 0.6
(c) 0.67
(d) 0.9

B

Question. A rejector circuit is:
(a) series resonant circuit
(b) parallel resonant circuit
(c) LCR circuit
(d) None of these

B

Question. In an a.c. circuit V and I are given by V = 50 sin50t volt and I = 100 sin(50t + π/3) mA. The power dissipated in the circuit
(a) 2.5 kW
(b) 1.25 kW
(c) 5.0 kW
(d) 500 watt

B

Question. In highly inductive load circuit, it is more dangerous when
(a) We close the switch
(b) Open the switch
(c) Increasing the resistance
(d) Decreasing the resistance

B

(a) less power loss
(b) more power loss
(c) high current
(d) high resistance

A

Question. When an AC voltage of 220 V is applied to the capacitor
(a) the maximum voltage between plates is 220 V.
(b) the current is in phase with the applied voltage.
(c) the charge on the plates is not in phase with the applied voltage.
(d) power delivered to the capacitor is zero.

D

Question. A transformer is based on the principle of
(a) mutual induction
(b) self induction
(c) Ampere’s law
(d) X-ray crystallography

A

Question. 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 good absorber of heat

B

Question. A transformer is an electrical device used for
(a) Producing direct current
(b) Producing alternating current
(c) Changing D.C into A.C.
(d) Changing A.C. voltages

D

Question. The transformation ratio in the step-up transformer is
(a) one
(b) greater than one
(c) less than one
(d) the ratio greater or less than one depends on the other factor

B

Question. The output of a step-down transformer is measured to be 24 V when connected to a 12 watt light bulb. The value of the peak current is
(a) 1/√2A
(b) √2A
(c) 2A
(d) 2√V2A

A

Question. Power factor of an ac circuit is a measure of:
(a) virtual power
(b) power lost in the circuit
(c) mean power
(d) all the above

B

Question. 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.

B

Question. In LCR circuit the capacitance is changed from C to 4C. For the same resonant frequency, the inductance should be changed from L to
(a) 2L
(b) L/2
(c) L/4
(d) 4L

C

Question 7. An iron core transformer with a turns ratio of 8 : 1 has 120 V applied across the primary. The voltage across the
(a) 15 V
(b) 120 V
(c) 180 V
(d) 960 V

A

Question. Generators at a power station produce electric power at voltage
(a) 45 kW
(b) 50 kW
(c) 60 kW
(d) 25 kW

D

Question. In an AC circuit containing only capacitance, the current
(a) Leads the voltage by 180º
(b) Remains in phase with voltage
(c) Leads the voltage by 90º
(d) Lags the voltage by 90º

C

Question. In series resonant circuit:
(a) reactance is zero
(b) current is zero
(c) voltage is zero
(d) None of these

D

Question. Alternating current is transmitted at far off places
(a) At high voltage and low current
(b) At high voltage and high current
(c) At low voltage and low current
(d) At low voltage and high current

A

(a) depends on the amount of the electrolyte
(b) depends on the current in the electrolyte
(c) is a universal constant
(d) depends on the amount of charge passed through the electrolyte

C

Question. In pure inductive circuit current
(a) lags behind emf by π/2
(b) leads the emf by π/2
(c) lags behind emf by π
(d) leads the emf by π

A

Question. An electric circuit containing capacitor only suffers:
(a) equal resistance for A.C. and D.C.
(b) Resistance of A.C. > Resistance of D.C.
(c) Resistance for A.C. < Resistance of D.C.
(d) offers infinite resistance for D.C.

D

Question. A choke coil is used to control current in a circuit of
(a) ac only
(b) dc only
(c) both ac and dc
(d) None of these

A

Question. Two identical coaxial circular loops carry equal currents in the same direction. If the loops approach each other the current in
(a) Each increases
(b) Each decreases
(c) Each remains the same
(d) One increases whereas that in the other decreases

B

Question. An inductive coil has a resistance of 100?. When an AC signal of frequency 1000Hz is fed to the coil the applied voltage leads the current by 45?. What is the inductance of the coil?
(a) 10mH
(b) 12mH
(c) 16mH
(d) 20mH

C

Question. The working principle of choke coil is based on
(a) Conservation of angular momentum
(b) Self induction
(c) Mutual induction
(d) Conservation of momentum

B

Unseenpassage give Alternating Current Class 12 MCQ PDF Free Download, Answers, and Marking Scheme. Here we have provided you with Class 12 Physics Alternating Current MCQ to make your preparation better. A Student can view or download the chapter-wise MCQ Questions for Class 12 with answers to score good marks in the Class 12 ​board exam.

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MCQ on Alternating Current Class 12 helps students to understand the questions asked in the board exam. We have also other study materials for Class 12 like Sample papers, Previous year Questions Paper, NCERT Solutions, NCERT Books, etc. If you have any problem in regard to MCQ of Alternating Current Class 12 in English, write a comment in the box given below.

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