Four charges are arranged at the corners of a square ABCD of side d, as shown in Fig. Find the work required to put together this arrangement
(b) A charge `q_(0)` brought to the center E of the square, the four charges being held fixed at the corners . How much extra work in needed to do this ?

Answer

(i) zero,
(ii). `(1)/(4piepsi_(0))*(q^(2))/(a)`
(iii). `(1)/(4piepsi_(0))(q^(2))/(a)(1+(1)/(sqrt(2)))`
(iv). `(1)/(4piepsi_(0))(q^(2))/(a)(2+(1)/(sqrt(2)))`
(v). `(1)/(4piepsi_(0))(q^(2))/(a)(4+sqrt(2))`