physics : class12 Induced EMF : Induced Current : Electromagnetic Induction and Alternating Currents MCQ Questions and Answers
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Induced EMF
MCQ questions and answers.
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MCQ Questions
1. According to Faraday's law of electromagnetic induction, the induced emf in a circuit is proportional to the:
A.
Magnetic flux through the circuit
B.
Rate of change of magnetic flux through the circuit
C.
Resistance of the circuit
D.
Electric charge in the circuit
Correct Answer:
Rate of change of magnetic flux through the circuit
Explanation:
Faraday's law states that the magnitude of induced emf is equal to the rate of change of magnetic flux linked with the circuit.
2. What is the SI unit of induced emf?
A.
Ampere
B.
Ohm
C.
Volt
D.
Weber
Correct Answer:
Volt
Explanation:
Induced emf is a potential difference, and its SI unit is the volt.
3. If the magnetic flux linked with a coil does not change, the induced emf in the coil is:
A.
Maximum
B.
Zero
C.
Infinite
D.
Equal to the resistance
Correct Answer:
Zero
Explanation:
Induced emf is produced only when the magnetic flux changes. If the flux remains constant, its rate of change is zero, so the induced emf is zero.
4. The magnitude of induced emf in a coil having N turns is given by:
A.
N times the rate of change of magnetic flux
B.
The magnetic flux divided by N
C.
N times the magnetic flux
D.
The resistance multiplied by N
Correct Answer:
N times the rate of change of magnetic flux
Explanation:
Faraday's law for a coil is expressed as the magnitude of induced emf equal to N times the rate of change of magnetic flux through one turn.
5. A coil has 10 turns, and the magnetic flux through each turn changes by 0.2 weber in 1 second. What is the magnitude of the induced emf?
A.
0.02 V
B.
0.2 V
C.
2 V
D.
20 V
Correct Answer:
2 V
Explanation:
Using induced emf = N times change in flux divided by time, emf = 10 × 0.2 / 1 = 2 V.
6. The negative sign in Faraday's law represents:
A.
The resistance of the coil
B.
Lenz's law
C.
The strength of the magnetic field
D.
The number of turns in the coil
Correct Answer:
Lenz's law
Explanation:
The negative sign shows that the induced emf opposes the change in magnetic flux that produces it, which is Lenz's law.
7. A straight conductor of length 0.5 m moves at 4 m/s perpendicular to a magnetic field of 2 T. What emf is induced across the conductor?
A.
1 V
B.
2 V
C.
4 V
D.
8 V
Correct Answer:
4 V
Explanation:
For motion perpendicular to the magnetic field, the motional emf is given by emf = B l v = 2 × 0.5 × 4 = 4 V.
8. Which change will increase the induced emf in a coil?
A.
Decreasing the rate of change of magnetic flux
B.
Increasing the number of turns in the coil
C.
Keeping the magnetic flux constant
D.
Removing the coil from the magnetic field without motion
Correct Answer:
Increasing the number of turns in the coil
Explanation:
The induced emf is proportional to the number of turns, so increasing the number of turns increases the induced emf for the same rate of flux change.
9. A magnetic flux changes from 1 Wb to 3 Wb in 2 seconds in a single-turn coil. What is the magnitude of the induced emf?
A.
0.5 V
B.
1 V
C.
2 V
D.
4 V
Correct Answer:
1 V
Explanation:
The induced emf is equal to the change in flux divided by time: (3 - 1) / 2 = 1 V.
10. An emf is induced in a closed coil when there is a change in the:
A.
Magnetic flux linked with the coil
B.
Mass of the coil
C.
Color of the coil
D.
Length of the connecting wire only
Correct Answer:
Magnetic flux linked with the coil
Explanation:
A changing magnetic flux linked with a coil produces an induced emf according to Faraday's law of electromagnetic induction.
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