Thus the total force F1 on q1 due to the two charges q2 and q3 is
given as
F
F
F
r
r
1
12
13
0
1
2
12
2
12
0
1
3
13
2
13
41
41
=
+
=
+
π
π
ε
ε
rq q
rq q
ˆ
ˆ
(1 4)
The above calculation of force can be generalised to a system of
charges more than three, as shown in Fig 1 5(b)