Shows a wire ab of length l and resistance R which can slide on a smooth pair of rails. `I_g` is a current generator which supplies a constand current in in the circuit. If the wire ab slides at a speed v towards right, find the potential difference betwwen `a and b`.

Explanation

The moving wire ab is equivalent to a battery of emf vBl having a resistance R
if it moves towards right and the magnetic field is going into the plane of the figure, the force` vec qv X vecB` will push the positive charges towards a
Thus the positive terminal of the equivalent battery is towards a
An equivalent circuit is shown in fiegur
the potential difference between a and b is ` V_a - V_b = vBl - iR`