A rolling axle, 1.50 m long, is pushed along horizontal rails at a constant speed v=3.00 m/s. A resistor R=0.400Ω
is connected to the rails at points a and b, directly opposite from each other. ( the wheels make good electrical contact with the rails, so the axle, rails, and R form a closed-loop circuit). A uniform magnetic field B=0.800T is directed vertically downward. (a) Find the induced current I in the resistor. (b) What horizontal force F is required to keep the axle rolling at constant speed?(c) Which end of the resistor, a or b, is at the higher electrical potential? (d) After the axle rolls past the resistor, does the current in R reverse direction?