Two electric charges 12 `mu` C and -6`mu`C are placed 20 cm apart in air, there will be a point P at which electric potential is zero on the line joining these two charges and out side excluding the region between them. The distance of P from -6 `mu`C charge is

Options

A. 0.1. m
B. 0.15 m
C. 0.20 m
D. 0.25 m

Answer

( c)

Explanation

Total potential at point is zero .Then,
`1/4 pi epsilon_(0) q_(1)/(r + x) + 1/4pi epsilon_(0) q_(2)/x = 0`
`rArr 12 xx 10^(6)/(20 + x) + (-6 xx 10^(-6))/x = 0`
`rArr 12 xx 10^(-6)/20 + x = 6 xx 10^(-6)/x`
On solving we get,
`rArr ` x = 20cm = 0.2 m