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
-(a) $\vec{E}=0$ at point $P$ in the unprimed frame.

Question

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
-(a) $\vec{E}=0$ at point $P$ in the unprimed frame.

Quizplus · Accepted Answer

Without the context of what $\vec{E}$ and point $P$ refer to, it's impossible to definitively say whether $\vec{E}=0$ at point $P$ in any given frame. However, in physics, $\vec{E}$ often represents the electric field, and it's entirely possible for the electric field to be zero at a specific point in space under certain conditions, such as at the midpoint between two equal but opposite charges.

Consider a Proton That in the Unprimed Frame Is at Rest