A coil is placed in a magnetic field B as shown below: A current is induced in the coil because B is: (a) Outward and decreasing with time (b) Parallel to the plane of coil and decreasing with time (c) Outward and increasing with time (d) Parallel to the plane of coil and increasing with time

Answer: (a). The induced current shown is anticlockwise, which produces an outward field inside the coil. By Lenz's law, the induced field opposes the change, so the outward flux must be decreasing (or an inward one increasing). A field parallel to the plane gives no flux and no induced current. So B is outward and decreasing, answer (a).

A coil is placed in a magnetic field B as shown below: A current is… | JEE Main 2021 (31 Aug, Shift 2)

Q22JEE Main 2021 · 31 AUG · SHIFT 2Medium

Lenz's Law, Eddy Currents & Induced Electric Field

A coil is placed in a magnetic field $\vec{B}$ as shown below:

A current is induced in the coil because $\vec{B}$ is:

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Answer: (a)

The induced current shown is anticlockwise, which produces an outward field inside the coil.
By Lenz's law, the induced field opposes the change, so the outward flux must be decreasing (or an inward one increasing).
A field parallel to the plane gives no flux and no induced current.
So $\vec{B}$ is outward and decreasing, answer (a).

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Lenz's Law, Eddy Currents & Induced Electric Field question from JEE Main 2021 (31 Aug, Shift 2)

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