A circular loop of radius r carrying a current i is held at the centre of another circular loop of radius R(>> r) carrying a current I. The plane of the smaller loop makes an angle of `30^@` with that of the larger loop. It the smaller loop is held fixed in this position by applying a single force at a point on its periphery, what would be the minimum magnitude of this force?

Explanation

As we have seen above,
Torque = iAB sin theta
`rArr F.r = i. pir. (mu_oI)/(2R) sin 30`
`rArr F = (mu_opiIir)/(4R)`
This is sufficient force to balance the given
condition.