Shows a conducting circular loop radius a placed in a uniform, perpendicular magnetic field B. A

Shows a conducting circular loop radius a placed in a uniform, perpendicular magnetic field B. A metal rod OA is pivoted at the centre O of the loop. The other A of the rod touches the loop. The rod OA and the loop are resistanceless but a resistor having a resistance R is connected between O and a fixed point C on the loop . the rod OA is made to rotate anticlockwise at a small but uniform angular speed omega by an external force. Find (a) the current in the resistance R and (b) the torque of the external force needed ot keep the rod rotating with the constant angular velocity omega.