Question

Three large plates $\text{A}$, $\text{B}$ and $\text{C}$ are placed parallel to each other and charges are shown in the figure. The charge that appears on left surface of plate $\text{B}$ is

• A. $6\text{C}$
• B. $3\text{C}$
• C. $-6\text{C}$
• D. $8\text{C}$

Answer 1

The correct option is A $6\text{C}$

The charge induced on outer surfaces of plates $\text{A}$ and plate $\text{C}$ is equal to the half of the sum of charges of all plates.

So, induced charges on these surfaces,

$q_1=q_2=\frac{-3+4+5}{2}=3\text{C}$

Since the charge on left side of plate $\text{A}$ is $3\text{C}$, so from principle of charge conservation, the charge on its rightside i.e. on the face $2$ is,

$q_2=-3-q_1=-3-3=-6\text{C}$

$\therefore q_2=-6\text{C}$

Since the surfaces $2$ and $3$ are facing each other, so the surface $3$ will have equal and opposite charge of surface $2$.

Hence, $q_3=-q_2=-(-6)\text{C}=+6\text{C}$

So, the charge on the left surface of plate $\text{B}$ is $6\text{C}$.


Hence, option (a) is the correct answer.