9
E
p
r
= 4
3
π
0ε
(r/a >> 1)
8
12
2
–1
–2
5 10
Cm
4
(8 854 10
C N
m
)
−
−
×
=
π
×
3
6
3
1
(15)
10
m
−
×
×
=  1 33 × 105  N C–1 The direction of electric field in this case is opposite to the direction
of the dipole moment vector