Rationalised 2023-24
Electric Charges
and Fields
13
 EXAMPLE 1 5
Thus,
Force F1 on Q due to charge q at A  = 
43
0
2
πε
lQq
 along AO
Force F2 on Q due to charge q at B  = 
43
0
2
πε
lQq
 along BO
Force F3 on Q due to charge q at C  = 
43
0
2
πε
lQq
 along CO
The resultant of forces F2 and F3 is 
43
0
2
πε
lQq
 along OA, by the
parallelogram law Therefore, the total force on Q = 
43
0
2
πε
lQq
ˆ
ˆ
r
(−r
)
 = 0, where ˆr
is the unit vector along OA It is clear also by symmetry that the three forces will sum to zero