Question

Two charges + q each are kept ‘2a’ distance apart. A third charge − 2q is placed midway between them. The potential energy of the system is ______. 

विकल्प

• `q^2/(8piepsilon_0a)`

• `-(6q^2)/(8piepsilon_0a)`

•   `(-7q^2)/(8piepsilon_0a)`

•   `(9q^2)/(8piepsilon_0a)`

Answer 1

Two charges + q each are kept ‘2a’ distance apart. A third charge − 2q is placed midway between them. The potential energy of the system is `bbunderline((-7q^2)/(8piepsilon_0a))`.

Explanation:

The potential energy of the system

`U = (kq^2)/(2a) - (-k2q^2)/a xx 2`

⇒ `U = (kq^2 - 8kq^2)/(2a)`

= `(-7kq^2)/(2a)`

So, `U = (-7q^2)/(8piepsilon_0a)`