MCQs on Electromotive Force (EMF) for NEET 2020

Electromotive force is the electric potential that is produced by a changing magnetic field or an electrochemical cell. The electromotive force is measured in volts.

Q1. The flux used in the equation for the calculation of induced emf in a transformer is in its

  1. RMS value
  2. Average value
  3. Maximum value
  4. Twice that of the maximum value

Answer: (c) Maximum value

Q2: What should be the value of primary to the secondary ratio for  a transformer to be an isolation transformer?

  1. Equal to one
  2. Less than one
  3. More than one
  4. Equal to 0.5

Answer: (a) Equal to one

Q3. The average emf induced per turn in a transformer is given by

  1. 1.11f Φm
  2. 0.5f Φm
  3. 4f Φm
  4. 8f Φm

Answer : (c) 4f Φm

Q4. Who introduced the right-hand rule for determining the direction of the induced EMF?

  1. Fleming
  2. Lenz
  3. Maxwell
  4. Faraday

Answer: (a) Fleming

Q5. Whenever there is a change in magnetic flux with respect to an electric conductor or a coil, an EMF is induced in the conductor is Faraday’s

  1. first law
  2. third law
  3. second law
  4. fourth law

Answer: (a) first law

Q6. Power of battery having emf E1=20V is

  1. 44.2 Watt
  2. 30.8 Watt
  3. 13.4 Watt
  4. 20 Watt

(c) Answer: (a) 44.2 Watt

Q7: In which device is the principle of statically induced emf used?

  1. Transformer
  2. Motor
  3. Generator
  4. Battery

Answer: (a)Transformer

Q8: Statically induced emf’s magnitude depends on the

  1. Rate of change of flux
  2. Coil resistance
  3. Flux magnitude
  4. None of these

Answer: (a) Rate of change of flux

Q9: Which is the property of a coil by which a counter emf is induced when the current through the coil changes?

  1. Self-inductance
  2. Mutual inductance
  3. Capacitance
  4. None of these

Answer: (a) Self-inductance

Q10: Principle of dynamically induced emf is used in a

  1. Choke
  2. Transformer
  3. Generator
  4. Thermo-couple

Answer: (c) Generator

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