As Shown in the Figure,a Metal Bar Is in Contact $\vec { B }$

Multiple Choice

As shown in the figure,a metal bar is in contact with a pair of parallel rails and is in motion with an upward velocity of magnitude ν.A uniform magnetic field is present, $\vec { B }$ field vector directed downward as shown.The direction of the induced current through the resistor R is

A) from a to b.
B) from b to a.
C) No current is induced.