physics : class12 Faraday’s Law : Induced Current : Electromagnetic Induction and Alternating Currents MCQ Questions and Answers
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Faraday’s Law
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 proportional to the rate of change of magnetic flux linked with the circuit.
2. The mathematical expression for the magnitude of induced emf in a coil is:
A.
E = IR
B.
E = qV
C.
E = -N dΦ/dt
D.
E = BIL
Correct Answer:
E = -N dΦ/dt
Explanation:
Faraday's law is expressed as E = -N dΦ/dt, where N is the number of turns and Φ is the magnetic flux through one turn.
3. If the magnetic flux linked with a single-turn coil changes by 2 Wb in 1 second, the magnitude of the induced emf is:
A.
0.5 V
B.
1 V
C.
2 V
D.
4 V
Correct Answer:
2 V
Explanation:
For one turn, the induced emf is the rate of change of flux: E = ΔΦ/Δt = 2 Wb/1 s = 2 V.
4. A coil has 100 turns, and the magnetic flux through each turn changes at a rate of 0.02 Wb/s. 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 Faraday's law, E = N(dΦ/dt) = 100 × 0.02 V = 2 V.
5. When the magnetic flux linked with a closed coil remains constant, the induced emf in the coil is:
A.
Zero
B.
Maximum
C.
Equal to the resistance
D.
Equal to the magnetic flux
Correct Answer:
Zero
Explanation:
Faraday's law shows that induced emf depends on the rate of change of flux. If the flux is constant, its rate of change is zero, so no emf is induced.
6. The SI unit of magnetic flux used in Faraday's law is:
A.
Tesla
B.
Weber
C.
Henry
D.
Volt
Correct Answer:
Weber
Explanation:
Magnetic flux is measured in weber (Wb), and Faraday's law relates its rate of change to induced emf.
7. A coil has 50 turns. If the magnetic flux through each turn changes by 0.1 Wb in 5 seconds, the induced emf is:
A.
0.1 V
B.
0.5 V
C.
1 V
D.
5 V
Correct Answer:
1 V
Explanation:
The induced emf is E = N(ΔΦ/Δt) = 50 × (0.1/5) = 1 V.
8. The negative sign in Faraday's law indicates the:
A.
Magnitude of the resistance
B.
Direction of the induced emf
C.
Number of turns in the coil
D.
Unit of magnetic flux
Correct Answer:
Direction of the induced emf
Explanation:
The negative sign in E = -N dΦ/dt represents the direction of the induced emf relative to the change in magnetic flux.
9. For the same change in magnetic flux and the same time interval, which coil produces the greatest induced emf?
A.
A coil with 10 turns
B.
A coil with 20 turns
C.
A coil with 50 turns
D.
A coil with 100 turns
Correct Answer:
A coil with 100 turns
Explanation:
Faraday's law states that induced emf is directly proportional to the number of turns. Therefore, the 100-turn coil produces the greatest emf.
10. If the rate of change of magnetic flux through a coil is doubled while the number of turns remains unchanged, the induced emf becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Zero
Correct Answer:
Double
Explanation:
According to Faraday's law, induced emf is directly proportional to the rate of change of magnetic flux. Doubling that rate doubles the induced emf.
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