In a coil, when current changes from 10 A to 4 A in 1 s. An induced emf of 1.2 V is induced across the coil. The self - inductance of the coil is:
Correct answer: B. 0.2 H
- A. 2 H
- B. 0.2 H
- C. 0.002 H
- D. 5 H
- E. 6 H
Explanation
To find the self-inductance L of the coil, we use the formula L = V / (ΔI/Δt), where V is the induced emf, ΔI is the change in current, and Δt is the time duration over which this change occurs. The change in current ΔI is calculated as the initial current minus the final current, or 10 A - 4 A = 6 A. The rate of change of current is therefore 6 A/s, since it occurs over 1 second. The induced emf (V) is given as 1.2 V. Plugging these values into the formula gives us L = 1.2 V / 6 A/s = 0.2 H. Other options are incorrect because they do not correspond with the calculated self-inductance using the given values and formula.
This question appeared on the NUMS 2019 (cancelled sitting) paper, which you can sit online with every answer explained.
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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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