A loop of flexible wire of irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire. (a) Loop assumes circular shape with its plane normal to the field. (b) Loop assumes circular shape with its plane parallel to the field. (c) Wire gets stretched to become straight. (d) Shape of the loop remains unchanged.

Answer: (a). A current loop tends to take the position of maximum magnetic flux through it (minimum energy U = -m · B). For a fixed length of wire, the circle encloses the largest area, and the flux is largest with the plane normal to B. So the answer is (a).

A loop of flexible wire of irregular shape carrying current is placed… | JEE Main 2021 (18 Mar, Shift 1)

Q43JEE Main 2021 · 18 MAR · SHIFT 1Easy

Force on Current-Carrying Conductors

A loop of flexible wire of irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire.

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Answer: (a)

A current loop tends to take the position of maximum magnetic flux through it (minimum energy $U = -\vec{m} \cdot \vec{B}$ ).
For a fixed length of wire, the circle encloses the largest area, and the flux is largest with the plane normal to $\vec{B}$ .
So the answer is (a).

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