Question

Two charges +q and +2q are placed at the ends of a
straight line. Another charge +q is placed at the mid-
point of the line. Then the charge +q (placed at the
mid-point) will:​

Answer 1

Answer:

The force on a charge Q due to another charge q at a distance d is given by: F=

4πϵ

0

1

d

2

Qq

The force is attracting for charges of opposite signs and repelling for same sign.

Since the force is proportional to the charge of other particle, and inversely proportional to square of distance, under equilibrium,

4πϵ

0

1

d

1

2

Q(−q)

+

4πϵ

0

1

d

2

2

Q(+2q)

=0

⟹d

2

=

2

d

1

The charge Q cannot be between the charges, because otherwise both −q and +2q would exert forces in same direction.

Hence, the charge lies on line joining two charges and on left of −q because the distance of Q from −q, d

1

is lesser than that from +2q, d

2

.