Question

Three large plates A, B and C are placed parallel to each other and charges are given as shown. The charge on left surface of B, if B and C both are earthed is :

• A. $5C$
• B. $6C$
• C. $3C$
• D. $-3C$

Answer 1

Answer: (B)

$6C$

$\text{Given:-}$ Charges $=-3C,4Cand5C$

$\text{Solution:-}$

Charge induced on outer surface of plate A and C will be half of sum of the total charges.

So charge induced $=\frac{-3+4+5}{2}C$

$=\frac{6}{2}C$

$=3C$

Charge on soft side of plate A is $3C$ so on right side of plate charge will be

$\Rightarrow 6C-3C=3C+x$ (where x is charge on right)

To make total Charge on plate $A-3C.$

So charge on right side of plate A will be $-6C$ and by law of induction charge on left side of plate B will be $+6C$

So, $6C$ charge appears on left surface of plate B

$\text{Hence the correct option is B}$