An emf of 5 volt is produced by a self inductance, when the current changes at a steady rate from 3 to 2 ampere in 1 millisecond. The value of self inductance is_______?
Correct answer: D. 5 mH
- A. zero
- B. 5 H
- C. 5000 H
- D. 5 mH
Explanation
The self-induced emf has magnitude E = L|ΔI/Δt|. Here |ΔI| = |2 A - 3 A| = 1 A and Δt = 1 ms = 0.001 s, so |ΔI/Δt| = 1 A ÷ 0.001 s = 1000 A s^-1. Hence L = 5 V ÷ 1000 A s^-1 = 0.005 H = 5 mH. The likely choice is c, because failing to convert milliseconds to 0.001 s produces a value that is 1,000 times too large.
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About Faraday's Law
Faraday's law states that an induced electromotive force equals the rate of change of magnetic flux linkage through a circuit. Questions cover changing field, area, angle or motion, the negative sign associated with Lenz's law, and the distinction between induced emf and the current that may flow in a closed circuit.
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