A coil of area A and N turns is rotating with angular velocity ω in a uniform magnetic field B about an axis perpendicular to B. Magnetic flux φ and induced emf ε across it, at an instant when B is parallel to the plane of coil, are: (a) φ = AB, ε = NABω (b) φ = AB, ε = 0 (c) φ = 0, ε = 0 (d) φ = 0, ε = NABω

Answer: (d). B parallel to the plane of coil means the area vector is perpendicular to B ( θ = 90°). φ = BAcos 90° = 0 e = NABωsin 90° = NABω (maximum) So the answer is (d) φ = 0, ε = NABω.

A coil of area A and N turns is rotating with angular velocity ω in a… | JEE Main 2025 (29 Jan, Shift 1)

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Rotating Conductors & AC Generator

A coil of area A and N turns is rotating with angular velocity $\omega$ in a uniform magnetic field $\vec{B}$ about an axis perpendicular to $\vec{B}$ . Magnetic flux $\varphi$ and induced emf $\varepsilon$ across it, at an instant when $\vec{B}$ is parallel to the plane of coil, are:

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Answer: (d)

$\vec{B}$ parallel to the plane of coil means the area vector is perpendicular to $\vec{B}$ ( $\theta = 90^\circ$ ).
$\phi = BA\cos 90^\circ = 0$
$e = NAB\omega\sin 90^\circ = NAB\omega$ (maximum)
So the answer is (d) $\varphi = 0$ , $\varepsilon = NAB\omega$ .

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