A thin circular wire of radius r has a charge Q. If a point charge q is placed at the centre of the ring, then find the increase in tension in the wire.

A ring of radius R has uniformly distributed charge q. A point charge Q is placed at the centre of the ring. (a) Find the increase in tension in the ring after the point charge is placed at its centre. (b) Find the increase in force between the two semicircular parts of the ring after the point charge is placed at the centre. (c) Using the result found in part (b) find the force that the point charge exerts on one half of the ring.

A ring of radius R is with a uniformly distributed charge Q on it .A charge q is now placed in the centre of the ring .Find the increment in tension in the ring.

A ring of radius R with a uniformly distributed charge q as shown in figure. A charge q_(0) , is now placed at the centre of the ring. Find the increment in-the tension in ring.

A thin spherical conducting shell of radius R has a charge q. Another charge Q is placed at the centre of the shell. The electrostatic potential at a point P a distance R/2 from the centre of the shell is