This means that we consider
the charges q1 and q2 initially at infinity and determine the work done by
an external agency to bring the charges to the given locations Suppose,
first the charge q1 is brought from infinity to the point r1 There is no
external field against which work needs to be done, so work done in
bringing q1 from infinity to r1 is zero This charge produces a potential in
space given by
V
rq
1
0
1
1
=41
πε
P
where r1P is the distance of a point P in space from the location of q1