A uniformly charged sphere has charge Q. An electron (charge – e, mass m) revolves around it in a circular orbit of radius r. (a) Write the total energy (i.e., sum of its kinetic energy and electrostatic potential energy in the field of the sphere) of the electron. (b) If the time period of revolution of the electron in circular orbit of radius r is T, then find the time period if the orbital radius is made 4r.