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The current in a circuit falls from 5 A to 0 A in 0.1 s. If an average emf of 200 V is induced, what is the self-inductance of the circuit?

Asked in GSEB Board July 2023 · Self-inductance and self-induced EMF

• (1) 0.5 H
• (2) 0.4 H
• (3) 5 H
• (4) 4 H

Step-by-step solution

Why the other options are wrong

• (1) No single slip gives 0.5 H. Sanity check: with this change of current (50 A s⁻¹), 0.5 H would induce only 25 V, not 200 V.
• (2) Takes the time as 0.01 s instead of 0.1 s: (200×0.01)/5 = 0.4 H — a misplaced decimal in Δ t.
• (3) 5 is the size of the current change, not the inductance. No working with these data gives 5 H; it would need an emf of 250 V.

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