A conducting circular loop of radius r is rotated about its diameter at a constant angular velocity `omega` in a magnetic field B perpendicular to the axis of rotation. In what position of the loop is the induced emf zero?

Explanation

suppose, the normal to the loop is parallel to the magnetic field at t=o
at time t, the normal will make an angle`theta = omega t with this position
The flux of the magnetic field through the loop is `Phi B pir^2 cos omega t` so that the induced emf at time t is ` epsilon = omega B pi r ^2 sin omega t`
This is zero when omegat = n pi, i
e
, when theta, pi 2pi,



, etc
these are the positons when the plane of the loop is normal to the magnetic field
It may be noted that at these positions, the flux has the maximum magnitude