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
- RMS value
- Average value
- Maximum value
- 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?
- Equal to one
- Less than one
- More than one
- Equal to 0.5
Answer: (a) Equal to one
Q3. The average emf induced per turn in a transformer is given by
- 1.11f Φm
- 0.5f Φm
- 4f Φm
- 8f Φm
Answer : (c) 4f Φm
Q4. Who introduced the right-hand rule for determining the direction of the induced EMF?
- Fleming
- Lenz
- Maxwell
- 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
- first law
- third law
- second law
- fourth law
Answer: (a) first law
Q6. Power of battery having emf E1=20V is
- 44.2 Watt
- 30.8 Watt
- 13.4 Watt
- 20 Watt
(c) Answer: (a) 44.2 Watt
Q7: In which device is the principle of statically induced emf used?
- Transformer
- Motor
- Generator
- Battery
Answer: (a)Transformer
Q8: Statically induced emf’s magnitude depends on the
- Rate of change of flux
- Coil resistance
- Flux magnitude
- 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?
- Self-inductance
- Mutual inductance
- Capacitance
- None of these
Answer: (a) Self-inductance
Q10: Principle of dynamically induced emf is used in a
- Choke
- Transformer
- Generator
- Thermo-couple
Answer: (c) Generator
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