Faraday's law ties induced emf to the rate of change of magnetic flux, and Lenz's law follows from conservation of energy, so this Class 12 sheet pairs the two induction laws. The weber as flux unit and an emf answer of 3 V also sit in the key.
Key Takeaways
Induced emf is proportional to the rate of change of magnetic flux (Q1).
Lenz's law follows from conservation of energy (Q2).
The weber is the unit of magnetic flux (Q3).
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.Faraday's law states that the induced emf is proportional to the rate of change of
(a) Electric field(b) Magnetic flux(c) Current(d) Resistance
2.Lenz's law is a direct consequence of the conservation of
(a) Charge(b) Energy(c) Momentum(d) Mass
3.The SI unit of magnetic flux is
(a) Tesla(b) Weber(c) Henry(d) Gauss
4.The SI unit of inductance is
(a) Tesla(b) Weber(c) Henry(d) Gauss
5.The direction of the induced current is given by
(a) Faraday's law(b) Lenz's law(c) Coulomb's law(d) Ohm's law
6.If the magnetic flux through a coil changes from 2 Wb to 8 Wb in 2 s, the magnitude of the induced emf is
(a) 2 V(b) 3 V(c) 6 V(d) 4 V
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.State Faraday's law of electromagnetic induction.
8.State Lenz's law.
9.Write the SI unit of magnetic flux.
10.Write the SI unit of inductance.
11.Write the expression for the induced emf in terms of the rate of change of magnetic flux.
12.Define magnetic flux.
13.Write the expression for the emf induced in an inductor due to a changing current.
14.Write the SI unit of magnetic flux density.
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.The magnetic flux through a coil changes from 4 Wb to 10 Wb in 2 s. Find the magnitude of the induced emf.
16.A coil of self-inductance 5 H has its current changed from 0 to 2 A in 0.5 s. Find the magnitude of the induced emf.
17.The magnetic flux through a coil changes from 20 Wb to 5 Wb in 3 s. Find the magnitude of the induced emf.
18.A coil of 100 turns has its flux changed by 0.01 Wb in 0.1 s. Find the magnitude of the induced emf.
19.The self-inductance of a coil is 2 H and the current through it changes at the rate of 3 A/s. Find the magnitude of the induced emf.
20.Explain how Lenz's law is consistent with the conservation of energy.
Answer Key
1. b) Magnetic flux
2. b) Energy
3. b) Weber
4. c) Henry
5. b) Lenz's law
6. b) 3 V
7. Refer to solution guide.
8. Refer to solution guide.
9. Refer to solution guide.
10. Refer to solution guide.
11. Refer to solution guide.
12. Refer to solution guide.
13. Refer to solution guide.
14. Refer to solution guide.
15. Refer to solution guide.
16. Refer to solution guide.
17. Refer to solution guide.
18. Refer to solution guide.
19. Refer to solution guide.
20. Refer to solution guide.
End of Worksheet
People Also Ask
What is induced emf proportional to?
The rate of change of magnetic flux, option (b) in this worksheet (Q1).
Which conservation law does Lenz's law follow from?
Conservation of energy, option (b) in this worksheet (Q2).
What is the unit of magnetic flux?
The weber, option (b) in this worksheet (Q3).
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