Consider the configuration of a system of four charges each of value (+q). Find the work done by external agent in changing the configuration of the system from (Fig. 3.44 A) to (Fig. 3.4B).
a. ,

Answer

`(-Kq^(2))/a (3-sqrt(2))`

Explanation

`U_("total")=U_(12)+U_(13)+U_(14)+U_(23)+U_(24)+U_(34)`
`U_("initial")=(Kq^(2))/a+(Kq^(2))/a+(Kq^(2))/(sqrt(2)a)+(Kq^(2))/a+(Kq^(2))/(sqrt(2)a)+(Kq^(2))/a`
`U_("final")=(Kq^(2))/(sqrt(2)a)+(Kq^(2))/(sqrt(2)a)+(Kq^(1))/(sqrt(2)a)+(Kq^(2))/(2a)+(Kq^(2))/(sqrt(2)a)`
`DeltaU=U_(f)-U_(i)=-(3-sqrt(2))(Kq^(2))/a`