Three charges `q, q_(2) and q_(3)` are placed in such a way that the distance `q_(1) and q_(2)" is "r_(12), q_(2) and q_(3) is r_(23) and q_(2) is r_(31)`.
a. What is the potential energy of the system?
b. In the above question if there are 'N' point charges, then what is thenet potential energy of the system? Give the expression.

Explanation

`U=U_(1)+U_(2)+U_(3)=(1)/(4pi epsi_(0)) {(q_(1)q_(2))/(r_(12))+(q_(2)q_(3))/(r_(23))+(q_(1)q_(3))/(r_(13))}`
b. Algebrac sum of PE of all attained pairs
i.e, `U=1/2 underset(i=1)overset(n)sum underset(j=1)overset(n)sum (1)/(4pi epsi_(0)) (q_(1)q_(j))/(r_(ij))" with i "ne j`