14)
For r >> a
E
p
=
44
0
q a3
πεr
ˆ                (r >> a)
(1 15)
(ii) For points on the equatorial plane
The magnitudes of the electric fields due to the two
charges +q and –q are given by
E
q
r
a
+q
=
+
4
1
0
2
2
πε
[1 16(a)]
E
q
r
a
–q
=
+
4
1
0
2
2
πε
[1 16(b)]
and are equal