Question

Two large plane parallel sheets shown in the figure have equal but opposite surface charge densities $+\sigma$ and $-\sigma$. A point charge q placed at points $P_1,P_2,P_3$ experiences forces $\overrightarrow{F_1},\overrightarrow{F_2},\overrightarrow{F_3}$ respectively. Then,

• A. $\overrightarrow F_1 = 0, \overrightarrow F_ 2 = 0, \overrightarrow F_3 = 0$
• B. $F_1 = 0, F_2 \neq 0, F_3 = 0$
• C. $F_1 \neq 0, F_2 \neq 0, F_3 \neq 0$
• D. $F_1 = 0, F_3 \neq 0, F_2=0$

Answer 1

Answer: (B)

$F_1 = 0, F_2 \neq 0, F_3 = 0$

Answer 2

The point charge placed at $P_1$ and $P_3,$ which are on the outer sides of the sheets, experiences no net force because the fields outside the sheets cancel out. However, the point charge at $P_2$ between the sheets experiences a net force due to the field between the oppositely charged sheets.