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Assertion (A) When a circular coil. placed in a region with its place parallel to a magnetic field, expands radially outwards, no emf is induced in it.
Reason (R) There is a constant magnet field in the perpendicular (to the plane of the coil) direction.
Options:
Reason (R) There is a constant magnet field in the perpendicular (to the plane of the coil) direction.
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Verified Answer
The correct answer is:
$A$ is true, $R$ is false.
When plane of a coil is parallel to magnetic field,
Flux linked with coil, $\phi_B=\mathbf{B} \cdot \mathbf{A}=0 \quad(\mathbf{B} \perp \mathbf{A}=0)$
So induced emf is zero.
$\therefore$ Assertion A is correct.
Reason $\mathrm{R}$ is incorrect as magnetic field is parallel to the plane of coil.
Flux linked with coil, $\phi_B=\mathbf{B} \cdot \mathbf{A}=0 \quad(\mathbf{B} \perp \mathbf{A}=0)$
So induced emf is zero.
$\therefore$ Assertion A is correct.
Reason $\mathrm{R}$ is incorrect as magnetic field is parallel to the plane of coil.
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