Question

Two charges each of Q unit are placed along aline.
A Therd charge - q is Placed on the line goining them.
what of Showd This (-q) Charge be placed
what of value so that the system is id equilibrium.​

Answer 1

Let the charge q be placed at 0, so that its distance from charge at A=x and from charge B=r−x.

Now, the system is in equilibrium, if electrostatic force on q due to charge at A= electrostatic force on q due to charge at B ie,

4πε

0

1

x

2

qQ

=

4πε

0

1

(r−x)

2

qQ

(r−x)

2

=x

2

or x=

2

r

Three charges will be in equilibrium if net force on each charge is zero i.e,

4πε

0

1

(

2

r

)

2

qQ

+

4πε

0

1

r

2

Q−Q

=0

or, q=

4

−