Question

Read the following and write the correct pairs. Initially, the two plates (A and B) are given charges as shown. Find the final charges on the plates after the key k is closed. All plates are conducting, parallel and of infinite length and breadth.

$\begin{array}{cccc}& \text{List-I}& & \text{List-II}\\ \text{(P)}& \text{Final charge on plate A}& \left(1\right)& \frac{Q}{2}\\ \text{(Q)}& \text{Final charge on plate B}& \left(2\right)& \text{Q}\\ \text{(R)}& \text{Final charge on plate C}& \left(3\right)& \text{0}\\ \text{(S)}& \text{Final charge on plate D}& \left(4\right)& \frac{3Q}{2}\end{array}$
Which of the following option has the correct combination considering column –I and column – II

• A. $P\to 3$
• B. $Q\to 4$
• C. $R\to 1$
• D. $S\to 3$

Answer 1

The correct option is D $S\to 3$



After switch is closed the charge on right side of plate $B(+\frac{3Q}{2})$ will try to go as far away from charge on left side $(+\frac{Q}{2})$
(As positive charges repel each other and wire provides path for travel).
So, charge $+\frac{3Q}{2}$ will go to plate C on right side.


Due to induction $-\frac{3Q}{2}$ will be induced on left side of plate D.
From conservation of charge, charge on right side of plate D is $-\frac{3Q}{2}$