A line charge λ per
unit length is lodged uniformly onto the rim of a wheel of mass M
and radius R. The wheel has light non-conducting spokes
and is free to rotate without friction about its axis (Fig. 6.22). A
uniform magnetic field extends over a circular region within the rim.
It is given by,
B = − B0 k (r ≤ a;
a < R)
= 0 (otherwise)
What is the angular
velocity of the wheel after the field is suddenly switched off?