Two equal point charges are fixed at x = -a and x = +a on the x-axis. Another point charge Q is placed at the origin. The change in the electrical potential energy of Q, when it is displaced by a small distance x along the x-axis, is approximately proportional to

Options

A. x
B. `x^(2)`
C. `x^(3)`
D. `1//x`

Answer

B

Explanation

`U_(i)=(2KQq)/(a)+(K.q.q)/(2a)`
and `U_(f)-KQq[(1)/(a+x)+(1)/(a-x)]+(K.q.q)/(2a)`
Here, `K=(1)/(4piepsi_(0))," "DeltaU=U_(f)-U_(i)" ""or"" "|DeltaU|=(2KQqx^2)/(a^3)`
For `xltlta" "therefore" "DeltaUpropx^(2)`