Two charged thin infinite plane sheets of uniform charge density $\sigma_+$ and $\sigma_-$, where $|\sigma_+| > |\sigma_-|$, intersect at right angle. Which of the following best represents the electric field lines for the system?
Answer: (C) Figure (C)
Each sheet produces a uniform field perpendicular to itself: $\dfrac{\sigma_+}{2\varepsilon_0}$ away from the positive sheet and $\dfrac{|\sigma_-|}{2\varepsilon_0}$ towards the negative sheet.
In every quadrant the resultant field is uniform, so the field lines are straight lines running from the positive sheet to the negative sheet.
The component perpendicular to the $\sigma_+$ sheet is larger, so each line meets the $\sigma_-$ sheet farther out than it left the $\sigma_+$ sheet, giving rhombus-shaped lines elongated along the $\sigma_-$ sheet, as in figure (C). Electrostatic field lines can never form closed loops, which rules out (B) and (D).
Solution by Sreeraj P, M.Sc Physics