Two fixed charges `-2Q` and `+Q` are located at points `(-3a,0)` and `(+3a,0)` respectively. Then which of the following statement is correct?

Options

A. Points where the electric potential due to the two charges is zero in x-y plane, lie on a circle radius 4a and centre (5a,0)
B. potential is zero at `x=a` and `x=9a`
C. both a and b are wrong
D. both a and b are correct

Answer

D

Explanation

Let P=(x,y)
`r_1=sqrt((x+3a)^2+y^2)`
`r_2=sqrt((x-3a)^2+y^2)`
`V_p=1/(4piepsilon_0)[Q/r_2-(2Q)/r_1]=0` ……..i
Sustituting vaues of `r_1` and `r_2` in eqn i we can see that equation is of a circle of radius `4a` and centre of `5a`.