20. arigid uniform horitontal wire pqof mass m, pivotea at p, carries a constant current i. it rotates with a constant angular speed in a uniform vertical magne

20. Arigid uniform horitontal wire PQof mass M, pivotea at P, carries a constant current I. It rotates with a constant angular speed in a uniform vertical magnetic field B. If the current were switched off, the angular acceleration of the wire, in terms of B, M and / would be P