Two charges `3x10^(-8)C` & `-2x10^(-8)C` are located 15 cm apart. At what point on the line joining the two charges is the electric potential zero? Take the potential infinity to be 0.

Explanation

Casc i) : For a point in between the two charges

For a net potential at P = 0, i.e., potential at .P. due to charge at A = potential .P. due to charge at B.
i.e, `" "V_(PA)=V_(PB)`
i.e., `" "(1)/(4pi epsilon_(0))(q_(A))/(AP)=(1)/(4pi epsilon_(0))(q_(B))/(BP)`
i.e, `(3xx10^(-8))/(0.15-x)=(2xx10^(-8))/(x)`
or `" "3x=0.3-2x`
or `" "5x=0.3`
x = 0.06 m too the left of `-2xx10^(-8)C`
Case ii) For a point outside the line joining the two point charges.

i.e., `" "(3xx10^(-8))/(0.15+x)=(2xx10^(-8))/(x)`
i.e., `" "3x=0.3+2x`
x = 0.3m to the right of `-2xx10^(-8)C`