A circular loop of radius R carries a current I. Another circular loop of radius r(ltltR) carries a current I. The plane of the smaller loop makes an angle of 90^@ with that of the larger loop. The planes of the two circles are at right angle to each other. Find the torque acting on the smaller loop.

Explanation

The magnetic field B at centre due to
larger loop. `B = (mu_oI)/(2R)`
Since current passed in smaller loop is i. so, required torque =i(vacA+vecB)`
[Here A = Area of smaller loop]
`=I AB sin 90^@`
`=i.pir^2. (mu_oI)/(2R)`
`=(mu_opi I. ir^2)/(2R)`