A conducting bar slides without friction on two parallel horizontal rails that are 50 cm apart and connected by a wire at oneend. The resistance of the bar and the rails is constant and equal to 0.10 Ω. A uniform magnetic field is perpendicular to theplane of the rails. A 0.080-N force parallel to the rails is required to keep the bar moving at a constant speed of 0.50 m/s. Whatis the magnitude of the magnetic field?
a. 0.36 Tb. 0.10 Tc. 0.54 Td. 0.93 Te. 0.25 T