GITAM, Department of Engineering Physics

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Torque on a Current Loop

The torque on a current-carrying coil,  can be related to the characteristics of the coil by the "magnetic moment" or "magnetic dipole moment".

Let a rectangular loop of wire of length ‘L’ and width ‘W’ and carrying a current ‘l’ , be suspended in a uniform field of magnetic induction B, with sides 1 and 3 always normal to the field direction.The torque exerted by the magnetic force (including both sides of the coil) is given by

The coil characteristics can be grouped as called the magnetic moment of the loop, and the torque written as The direction of the magnetic moment is perpendicular to the current loop in the right-hand-rule direction, the direction of the normal to the loop in the illustration. Considering torque as a vector quantity, this can be written as the vector product

 

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