Question

Two particles $A$ and $B$ having charges $20\mu C$ and $-5\mu C$ respectively are held fixed with a separation of $5cm$. At what position a third charged particle should be placed so that it does not experience a net electric force?

• A. At $5cm$ from $20\mu C$ on the left side of system
• B. At $5cm$ from $-5\mu C$ on the right side
• C. At $1.25cm$ from $-5\mu C$ between two charges
• D. At midpoint between two charges

Answer 1

Answer: (B)

$E_N=+\frac{k(-5\mu C)}{x^2}+\frac{k(20\mu C)}{(5+x{)}^2}=0$
$x=5cm$