A circular loop of radius 7 cm is placed in uniform magnetic field of… | JEE Main 2026 (23 Jan, Shift 2)

Q15JEE Main 2026 · 23 JAN · SHIFT 2Medium

Magnetic Flux & Faraday's Law

A circular loop of radius 7 cm is placed in uniform magnetic field of 0.2 T directed perpendicular to plane of loop. The loop is converted into a square loop in 0.5 s. The EMF induced in the loop is ______ mV.

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Answer: (c)

Same wire, so perimeter is constant: $2\pi r = 2 \times \frac{22}{7} \times 7 = 44$ cm, square side $= 11$ cm.
Circle area $= \frac{22}{7} \times 49 = 154$ cm $^2$ ; square area $= 121$ cm $^2$ ; $\Delta A = 33$ cm $^2 = 33 \times 10^{-4}$ m $^2$ .
$e = \frac{B\Delta A}{\Delta t} = \frac{0.2 \times 33 \times 10^{-4}}{0.5} = 1.32 \times 10^{-3}$ V
So the answer is (c) 1.32 mV.

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Magnetic Flux & Faraday's Law question from JEE Main 2026 (23 Jan, Shift 2)

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