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MHT CET 2025 (21 Apr, Shift 2) · Biot-Savart Law & Circular Coils

Biot-Savart Law & Circular Coils question from MHT CET 2025 (21 Apr, Shift 2)

Q24MHT CET 2025 · 21 APR · SHIFT 2Medium

Biot-Savart Law & Circular Coils

An electron moves in Bohr orbit. The magnetic field at the centre is proportional to

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Answer: (d)

$B = \frac{\mu_0 I}{2r}$ with $I = \frac{ev}{2\pi r}$ , so $B \propto \frac{v}{r^2}$ .
Bohr model: $v \propto \frac{1}{n}$ , $r \propto n^2$ .
$B \propto \frac{n^{-1}}{n^4} = n^{-5}$
So the answer is (d) $n^{-5}$ .

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