Alternating Current MCQ Questions for Class 12 Physics Chapter 7 with Answers

Find here the NCERT chapter-wise Multiple Choice Questions from Class 12 Physics book Chapter 7 Alternating Current with Answers Pdf free download. This may assist you to understand and check your knowledge about the chapters. Students also can take a free test of the Multiple Choice Questions of Alternating Current. Each question has four options followed by the right answer. These MCQ Questions are selected supported by the newest exam pattern as announced by CBSE.

Q1. Energy dissipates in LCR circuit in :

(i) L only
(ii) C only
(iii) R only
(iv) All of the above

(iii) R only

Q2. In an LCR circuit, capacitance is charged from C to 2C. For resonant frequency to remain unchanged, the inductance should be changed from L to

(i) 4 L
(ii) 2 L
(iii) L/2
(iv) L/4

(iii) L/2

Q3. As the frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit?

(i) Inductor and capacitor.
(ii) Resistor and inductor.
(iii) Resistor and capacitor.
(iv) None.

(i) Inductor and capacitor.

Q4. Alternating currents can be produced by a

(i) dynamo
(ii) choke coil
(iii) transformer
(iv) electric motor

(i) dynamo

Q5. In a pure capacitive circuit if the frequency of ac source is doubled, then its capacitive reactance will be

(i) remains same
(ii) doubled
(iii) halved
(iv) zero

(iii) halved

Q6. In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?

(i) Only resistor
(ii) Resistor and inductor
(iii) Resistor and capacitor
(iv) Only inductor

(iii) Resistor and capacitor

Q7. The dimensional formula of L/R is similar to that of:

(i) frequency
(ii) time
(iii) length
(iv) none of these

(ii) time

Q8. An ac circuit has a resistance of 12 ohm and an impedance of 15 ohm. The power factor of the circuit will be

(i) 0.8
(ii) 0.4
(iii) 0.125
(iv) 1.25

(i) 0.8

Q9. In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?

(i) Only resistor.
(ii) Resistor and an inductor.
(iii) Capacitor and an inductor.
(iv) Only a capacitor.

(iv) Only a capacitor.

Q10. The electric mains supply in our homes and offices is a voltage that varies like a sine function with time such a voltage is called … A… and the current driven by it in a circuit is called the … B… Here, A and B refer to

(i) DC voltage, AC current
(ii) AC voltage, DC current
(iii) AC voltage, DC voltage
(iv) AC voltage, AC current

(iv) AC voltage, AC current

Q11. A 100 turn coil of area 0.1 m2 rotates at half a revolution per second. It is placed in a uniform magnetic field of 0.01 T perpendicular to the axis of rotation of the coil. Calculate the maximum voltage generated in the coil?

(i) 256.33 V
(ii) 89.12V
(iii) 0.314 V
(iv) 3.1455 V

(iii) 0.314 V

Q12. In which of the following circuits the maximum power dissipation is observed?

(i) Pure capacitive circuit
(ii) Pure inductive circuit
(iii) Pure resistive circuit
(iv) None of these

(iii) Pure resistive circuit

Q13. Power factor of an ac circuit is a measure of:

(i) virtual power
(ii) power lost in the circuit
(iii) mean power
(iv) all the above

(ii) power lost in the circuit

Q14. In an LCR-series ac circuit, the voltage across each of the component L, C and R is 50 V. The voltage across the LC-combination will be

(i) 50 V
(ii) 50√2 V
(iii) 100 V
(iv) zero

(iv) zero

Q15. 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

(i) 1/√2A
(ii) √2A
(iii) 2A
(iv) 2√V2A

(i) 1/√2A

Q16. A.C. power is transmitted from a power house at a high voltage as

(i) the rate of transmission is faster at high voltages
(ii) it is more economical due to less power loss
(iii) power cannot be transmitted at low voltages
(iv) a precaution against theft of transmission lines

(ii) it is more economical due to less power loss

Q17. Identify the principle behind the working of an a.c. generator.

(i) Eddy currents
(ii) Faraday’s law
(iii) Lenz’s law
(iv) Electromagnetic induction

(iv) Electromagnetic induction

Q18. In a series LCR circuit the voltage across an inductor, capacitor and resistor are 20 V, 20 V and 40 V respectively. The phase difference between the applied voltage and the current in the circuit is

(i) 30°
(ii) 45°
(iii) 60°
(iv) 0°

(iv) 0°

Q19. An iron core transformer with a turns ratio of 8 : 1 has 120 V applied across the primary. The voltage across the

(i) 15 V
(ii) 120 V
(iii) 180 V
(iv) 960 V

(i) 15 V

Q20. Reciprocal of impedance is

(i) susceptance
(ii) conductance
(iii) admittance
(iv) transconductance

(iii) admittance

Q21. Transformer works on the principle of:

(i) convertor
(ii) invertor
(iii) mutual induction
(iv) self-induction

(iii) mutual induction

Q22. In which of the following circuits the maximum power dissipation is observed?

(i) Pure capacitive circuit
(ii) Pure inductive circuit
(iii) Pure resistive circuit
(iv) None of these

(iii) Pure resistive circuit

Q23. At resonant frequency the current amplitude in series LCR circuit is

(i) maximum
(ii) minimum
(iii) zero
(iv) infinity

(i) maximum

Q24. capacitor acts as an infinite resistance for

(i) DC
(ii) AC
(iii) DC as well as AC
(iv) neither AC nor DC

(i) DC

Q25. For an ideal-step-down transformer, the quantity which is constant for both the coils is

(i) current in the coils
(ii) voltage across the coils
(iii) resistance of coils
(iv) power in the coils

(iv) power in the coils

Q26. A rejector circuit is:

(i) series resonant circuit
(ii) parallel resonant circuit
(iii) LCR circuit
(iv) None of these

(ii) parallel resonant circuit

Q27. Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?

(i) R = 20, L= 1.5 H, C = 35 μF.
(ii) R = 25 , L = 2.5 H, C = 45 μF.
(iii) R = 15 , L = 3.5 H, C = 30 μF.
(iv) R = 25 , L = 1.5 H, C = 45 μF.

(iii) R = 15 , L = 3.5 H, C = 30 μF.

Q28. In pure inductive circuit current

(i) lags behind emf by π/2
(ii) leads the emf by π/2
(iii) lags behind emf by π
(iv) leads the emf by π

(i) lags behind emf by π/2

Q29. When an AC voltage of 220 V is applied to the capacitor C

(i) the maximum voltage between plates is 220 V.
(ii) the current is in phase with the applied voltage.
(iii) the charge on the plates is not in phase with the applied voltage.
(iv) power delivered to the capacitor is zero.

(iv) power delivered to the capacitor is zero.

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Class 12 Physics MCQ Questions with Answers

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