Consider a Proton That in the Unprimed Frame Is at Rest

Consider a proton that in the unprimed frame is at rest at point $P$ midway between two positively charged thin rods parallel to the $x$ axis. The top rod moves with speed $\mid \vec{v}$ in the $+x$ direction as shown. Both rods have the same charge per unit length $\lambda$ in the unprimed frame.

for section (d) consider viewing the situation in a primed frame in which the top rod is at rest. Specify the direction of
-the magnetic field vector $\vec{B}^{\prime}$

A) The vector points in the $+x$ direction.
B) The vector points in the $-x$ direction.
C) The vector points in the $+y$ direction.
D) The vector points in the $-y$ direction.
E) The vector points in the $+z$ direction.
F) The vector points in the $-z$ direction.
G) The vector is zero.