Question

Two point charges placed at a distance r in air exert a force F on each other.

At what distance will these charges experience the same force F in a medium

of dielectric constant K?​

Answer 1

Answer:

Correct option is

C

k

r

Two point charge placed at a certain distance =r

force =F

dielectric constant =k

Let, two point charges q

1

and q

2

are separated r distance from each other.

Then, force experienced between then,

F=

4πϵ

0

r

2

q

1

q

2

Put, F=

4πϵ

0

r

2

q

1

q

2

∴

4πϵ

0

r

2

4q

1

q

2

=

k(4πϵ

0

r

2

)

q

1

q

2

⇒

r

2

1

=

4r

2

h

1

⇒

r

2

1

=

kr

2

1

taking square root both sides

r

1

−

k

r

1

1

or, r

1

=

k

r