A coil of effective area 3 m ² is placed at right angles to a magnetic field of induction 0.05 Wb/m ². If the field is decreased to 20% of its original value in 10 second, the e.m.f. induced in the coil will be (a) 15 mV (b) 12 mV (c) 10 mV (d) 5 mV

Answer: (b). e = (A Δ B)/(Δ t) Field falls to 20%: Δ B = 0.8× 0.05 = 0.04 Wb/m ² e = (3× 0.04)/(10) = 0.012 V = 12 mV So the answer is (b) 12 mV.

A coil of effective area 3 m ² is placed at right angles to a… | MHT CET 2026 (20 Apr, Shift 1)

Q4MHT CET 2026 · 20 APR · SHIFT 1Easy

Magnetic Flux & Faraday's Law

A coil of effective area $3$ m $^{2}$ is placed at right angles to a magnetic field of induction $0.05$ Wb/m $^{2}$ . If the field is decreased to $20\%$ of its original value in $10$ second, the e.m.f. induced in the coil will be

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Answer: (b)

$e = \frac{A\,\Delta B}{\Delta t}$
Field falls to $20\%$ : $\Delta B = 0.8\times 0.05 = 0.04$ Wb/m $^{2}$
$e = \frac{3\times 0.04}{10} = 0.012$ V $= 12$ mV
So the answer is (b) $12$ mV.

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