Two charges 4q and q are placed 30 cm. apart. At what point the value of electric field will be zero

Options

A. 10 cm away from q and between the charges
B. 20 cm away from q and between the charges
C. 10 cm away from q and outside the line joining the charges
D. 10 cm away from 4q and outside the line joining them

Answer

A

Explanation

Position of null point is given by
`x_(1)=r/(sqrt((q_(2))/(q_(1)))+1)`
`x_(1)=30/(sqrt(4/1)+1)`
`x_(1)=10cm`