6)
from r¢ = ¥ to r¢ = r,
W
Q
r
dr
Q
r
Q
r
r
r
= −
′
′ =
′
=
∞
∞
∫ 4
4
4
0
2
0
0
π
π
π
ε
ε
ε
(2 7)
This, by definition is the potential at P due to the charge Q
0
( )
4
Q
V r
εr
=
π
(2 8)
FIGURE 2 2 Work done on a test charge q
by the electrostatic field due to any given
charge configuration is independent
of the path, and depends only on
its initial and final positions