In the Figure,a Copper Bar Is in Contact with a Pair

Multiple Choice

In the figure,a copper bar is in contact with a pair of parallel metal rails and is in motion with velocity ν.A uniform magnetic field is present pointing downward,as shown.The bar,the rails,and the resistor R are all in the same plane.The induced current through the resistor R is

A) from a to b.
B) from b to a.
C) There is no induced current through the resistor.