Question

Two small indentical conducting balls A and B of charges $+10\mu$C and $+30\mu$C, respectively, are kept at a separation of $50cm$. These balls have been connected by a wire for a short time. The force of interaction between the balls is :

• A. $28.8N$
  
• B. $32.6N$
  
• C. $14.4N$
  
• D. $72N$
  

Answer 1

Answer: (C)

$14.4N$

After connecting the balls by wire, charge on both the balls will be same and total charge remains constant
Charge on each ball is $\frac{10+30}{2}=20\mu C$
$F=k\frac{q_1{q}_2}{r^2}9\times {10}^9\times \frac{(20\times {10}^{-6}{)}^2}{(0.50{)}^2}=14.4N$