A uniform conducting bar of mass m and length L is pivoted at one end. At the other end it makes electrical contact (through brushes) with a conductor shaped like a ring of radius L, so that the bar forms a radius of the circle. A current I is fed into the bar at the pivot so that it flows from center to edge of the circle. There is also a uniform magnetic field B pointing into the page. Required:

a. Find the torque exerted on the bar (measured about the pivot) by the magnetic field. Which way is the torque? b. Recalling that the moment of inertia of a bar about one end is J=13ML2, find the angular acceleration of the bar. (Note that we are calling the moment J instead of I.)