A thin wire ring of radius `r` has an electric charge `q`. What will be the increment of the force stretching the wire if a point charge `q_(0)` is placed at the ring's centrre ?

Explanation

When the charge `q_(0)` is placed of the centre of the ring, the wire get streched and the extra tension, produced in the wire, will balance the electric force due to the charge `q_(0)` Let the tension produced in the wire, after placing the charge `q_(0)` be `T`. From Newton's second law in projection from `F_(n) = mw_(n)`.
`Td theta - (1)/(4pi epsilon_(0)) (q_(0))/(r^(2)) ((q)/(2pi r) rd theta) = (dm) 0`,
or, `T = (q q_(0))/(8 pi^(2) epsilon_(0) r^(2))`