A system consists of a him charged wire ring of radius R and a very uniformly charged thread oriented along the axis of the ring with one of its ends coinciding with the centre of the ring. The total charge of the ring is equal to q. The charge of the thread (per unit length) is equal to `lambda`. Find the interaction force between the ring and the thread.

Explanation

Force "dF" on the wire `=dq barE`
`=(qx lambda dx)/(4pi in_(0)(x^(2)+R^(2))^(3//2))`
`=(qlambda)/(4pi in_(0)) int_(0)^(oo) (xdx)/((R^(2) +x^(2))^(3//2))`
`F=(lambdaq)/(4pi in_(0)R)`.