Question

Charges 4Q, q and Q and placed along

x-axis at positions x=0, x=l/2 and x=l,

respectively. Find the value of q so that

force on charge Q is zero​

Answer 1

Answer:

The force exerted on the charge q,Q is given as follows.

F(q,Q)=k[

l

2

/4

qQ

]=

l

2

4kqQ

.

The force exerted on the charge q, 4q is given as follows.

F(q,4q)=k[

l

2

4q

2

]=

l

2

4kq

2

.

The net force = F(q,Q) + F(q,4q) = 0

l

2

4kqQ

+

l

2

4kq

2

=0

So, qQ+q

2

=0.

q[Q + q] =0

As, q cannot be = 0

Q + q =0

Therefore, Q = - q

Hence, Q should be -q in order to make the net force on q to be zero.