Page 16 - Electrostatics 11

Grade 11 © GC Shiba
Electric intensity at any point on the broadside on position or bisector of

dipole:
P
Let us consider a dipole of dipole moment P.

Here +q and -q charges are at a distance 2L and O is
the Centre of dipole. Let OP = r and from figure, r

2
2
2
2
= √ + and = √ + .
A B
Electric intensity at point P due to charge at point A +q O -q
is

⃗⃗⃗⃗⃗⃗
=

2
2
4 ( + )
0
Electric intensity at point P due to charge at point B is

⃗⃗⃗⃗⃗⃗
=

2
2
4 ( + )
0
Electric intensity at point P due to dipole is

= √ 2 + 2 + 2 2

, = ∠ = ∠

, =

= √1 + 1 + 2 2

= √2 + 2 2

= √2 + 2 2

= √2 √1 + 2 2

2
= 2 (∵ 2 = 2 − 1)

= 2 × ×
2
2
4 ( + ) √( + )
2
2
0

∴ = (∵ = × 2 )
2 3/2
2
4 ( + )
0
This is the required expression for intensity at point P due to dipole.
16 Electrostatics