Question

The charges on two sphere are $+7\mu C$ and $-5\mu C$ respectively. They experience a force F. If each of them is given and additional charge of $-2\mu C$ the new force of attraction will be

• A. F
• B. $\frac{F}{2}$
  
• C. $\frac{F}{\sqrt{3}}$
  
• D. 2F

Answer 1

The correct option is A F

$F=\frac{1}{4\pi {ϵ}_0}\frac{(+7\times {10}^{-6})(-5\times {10}^{-6})}{r^2}=-\frac{1}{4\pi {ϵ}_0}\frac{35\times {10}^{12}}{r^2}N$
$F^{\prime }=\frac{1}{4\pi {ϵ}_0}\frac{(+5\times {10}^{-6})(-7\times {10}^{-6})}{r^2}=-\frac{1}{4\pi {ϵ}_0}\frac{35\times {10}^{12}}{r^2}N$