1 21) Electric field due to the charge rDV is
given by Coulomb’s law:
2
0
1
ˆ
4
V
'
r'
ρ
ε
∆
∆
=
π
E
r
(1 26)
where r¢ is the distance between the charge element and P, and  ˆr¢ is a
unit vector in the direction from the charge element to P