Electromagnetic induction produces an induced e.m.f. when magnetic flux is cut, and Faraday's law ties it to the rate of change of flux linkage, so this Year 13 sheet opens with the two statements of induction. The weber as the flux unit follows in the answers.
Key Takeaways
An induced e.m.f. appears when magnetic flux is cut (Q1).
Induced e.m.f. relates to the rate of change of flux linkage (Q2).
The unit of magnetic flux is the weber (Q4).
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.Electromagnetic induction produces
(a) an induced e.m.f. when magnetic flux is cut(b) a static charge(c) a magnetic pole(d) a permanent magnet
2.Faraday's law relates the induced e.m.f. to
(a) the rate of change of flux linkage(b) the current in the circuit(c) the temperature(d) the resistance
3.Lenz's law states that the induced current
(a) opposes the change producing it(b) enhances the change producing it(c) flows in a random direction(d) depends on gravity
4.The unit of magnetic flux is the
(a) weber (Wb)(b) tesla(c) farad(d) henry
5.Magnetic flux linkage is given by
(a) NΦ (the number of turns × the flux)(b) Φ ÷ N(c) N ÷ Φ(d) N + Φ
6.The induced e.m.f. can be increased by
(a) increasing the number of turns on the coil(b) decreasing the number of turns(c) moving the magnet slowly(d) removing the coil
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.Define electromagnetic induction.
8.State Faraday's law.
9.State Lenz's law.
10.What is magnetic flux?
11.What is flux linkage?
12.What is the unit of magnetic flux density B?
13.Give one use of electromagnetic induction.
14.How is the magnitude of the induced e.m.f. calculated?
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A coil of 100 turns has a magnetic flux change of 0.02 Wb in 0.4 s. Using E = N × ΔΦ ÷ Δt, find the induced e.m.f.
16.A coil of 200 turns has a magnetic flux change of 0.05 Wb in 0.5 s. Using E = N × ΔΦ ÷ Δt, find the induced e.m.f.
17.A coil has 500 turns and a magnetic flux of 0.01 Wb. Using flux linkage = NΦ, find the flux linkage.
18.A transformer has 1000 primary turns and 200 secondary turns with a 240 V primary supply. Using Vp ÷ Vs = Np ÷ Ns, find the secondary voltage.
19.A magnetic field of flux density 0.5 T acts over an area of 0.2 m². Using Φ = BA, find the flux.
20.A coil of 50 turns has a magnetic flux change of 0.01 Wb in 0.2 s. Using E = N × ΔΦ ÷ Δt, find the induced e.m.f.
Answer Key
1. a) an induced e.m.f. when magnetic flux is cut
2. a) the rate of change of flux linkage
3. a) opposes the change producing it
4. a) weber (Wb)
5. a) NΦ (the number of turns × the flux)
6. a) increasing the number of turns on the coil
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
When does electromagnetic induction produce an e.m.f.?
When magnetic flux is cut, option (a) in this worksheet (Q1).
What does Faraday's law relate induced e.m.f. to?
The rate of change of flux linkage, option (a) in this worksheet (Q2).
What is the unit of magnetic flux?
The weber, option (a) in this worksheet (Q4).
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