As Shown in the Figure, a Straight Wire Carries a Steady

Multiple Choice

As shown in the figure, a straight wire carries a steady current $I$ . A metal bar is in contact with a pair of rails and is in upward motion with velocity of magnitude $v$ . The polarity of the induced emf in terminals $X$ and $Y$ is

A) $Y$ is positive and $X$ is negative.
B) $X$ and $Y$ are at the same potential.
C) $X$ is positive and $Y$ is negative.