A straight horizontal rod A of mass 50 gm and length 0.5 m, is placed in a uniform horizontal magnetic field of 0.2 T, perpendicular to A. Calculate the current in A if the force acting on it just balances it weight.

Answer 1

Require that
M g = B I L

Solve for I (amps). Make sure M is in kg.

I = M g/(B L)