Two point charges of +3x10^-8C and -2x10^-8C are located 15 cm apart in air. Find at what point on the line joining these charges the electric potential is zero. Take potential at infinity to be zero.

There will be two such points. One between the charges, and one external point on the side of -2 x 10^-8 C charge.

For internal point it will be 9 cm from 3 x 10^-8C charge and 6 cm from -2 x 10^-8 C charge.

For external point it will be 45 cm from 3 x 10^-8C charge and 30 cm from -2 x 10^-8 C charge.