Question

Force of attraction b/w two point charges placed at a distance d is F. What distance apart should they be kept in the same medium so that force b/w them is F/3 ? Explain clearly plz and fast.

Answer 1

Let us consider two point charges q1 and q2, placed at a distance d.
Force of attraction,
F = k (q1q2)/d²________(1)
Now, if the force becomes F/3, then let the distance between the point charges be r
Now, force of attraction,
F' = F/3 = k (q1q2)/r²______(2)
dividing equation, (1) and (2),we get
3 = r²/d²
⇒r² = 3 d²
⇒r = d√3
If the distance between them is d√3, the force will be F/3.

Answer 2

Consider two point charges q1,q2 At a distance D Force between them is F = kq1q2/d^2 Let the distance between the two charges be r when the force between them is F/3 F/3 = kq1q2/r^2 Dividing equation 2 by equation by 1 1/3 = d^2/r^2 r^2 = 3(d^2) r = √3 D There fore when the distance between the two point charges is √3d the force becomes F/3