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A circular loop carrying current I is replaced by a bar magnet of equivalent magnetic dipole moment. The point on the loop is lying ______.

Asked in RS Academy GUJCET booklet · Magnetic moment of magnets and loops

Answer: (1) on equatorial plane of magnet

Step-by-step solution

Idea: the moment of a current loop is ⃗m=IÂn, and ̂n is perpendicular to the plane of the loop. So the equivalent bar magnet sits at the centre of the loop with its axis along the loop's axis, at right angles to the loop's plane.

Now ask where a point of the ring itself lies with respect to that magnet.

It lies in the plane through the magnet's centre perpendicular to the magnet's axis -- which is precisely the equatorial, or broadside-on, plane.

By the same picture, a point on the loop's axis would be in the axial, or end-on, position. The two positions are 90° apart.

So a point on the loop lies on the equatorial plane of the equivalent magnet.

Why the other options are wrong

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