A very long bar magnet is placed with its north pole coinciding with the centre of a circular loop carrying an electric current i.
A very long bar magnet is placed with its north pole coinciding with the centre of a circular loop carrying an electric current i. The magnetic field due to the magnet at a point on the periphery of the wire is B. The radius of the loop is a. The force on the wire is
(a) very nearly 2πaiB perpendicular to the plane of the wire
(b) 2πaiB in the plane of the wire
(c) πaiB along the magnet
(d) zero.
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