Question

Two large plates are given the charges as shown in the figure. The left plate is now earthed. The amount of charge that will flow from earth to this plate is

• A. $14\mu \text{C}$
• B. $-14\mu \text{C}$
• C. $7\mu \text{C}$
• D. $-7\mu \text{C}$

Answer 1

The correct option is B $-14\mu \text{C}$

Given, initial charge on left plate, $q_i=10\mu \text{C}$


Since the final charges on the outer surfaces of both the plates should be $=0$.

The charges on inner surface of right plate $=(4-0)=4\mu \text{C}$

So, the final charge on inner surface of left plate,
$q_f=-4\mu \text{C}$

Thus, charge flow from the earth$=q_f-q_i=-4-10=-14\mu \text{C}$

Hence, option (b) is the correct answer.