Which one of the following graphs represents the variation of electric potential with distance r from the centre of a non-conducting charged sphere of radius R?
Four charges equal to + Q are placed at the four corners of a square and a charge ($$-$$q) is at its centre. If the system is in equilibrium, then the value of $$-$$q is
An electric dipole is placed at an angle of 30$$^\circ$$ in a non-uniform electric field. The dipole will experience
A charge +q is placed at the origin O of XY-axes as shown in the figure. The work done in taking a charge Q from A to B along the straight line AB is