Q11

A short copper rod $R$ is placed on a pair of thick horizontal parallel copper rails. A horizontal magnetic field exists in the direction shown by the dashed arrows. The diagram shows the apparatus when viewed from directly above.

When switch $S$ is closed, $R$ will tend to:
(A) Lift upwards away from the rails.
(B) Move to the left.
(C) Move to the right.
(D) Be pressed downwards onto the rails.