Draw the line of force for a hollow metallic sphere carrying a positive charge. Assume that the sphere is insulated from the earth and is also far away from any other charged or uncharged bodies. If a positive charge is brought near this charged sphere, will it still remain equipotential ? Explain.

An electric dipole is formed by two charges $q$ and $-q$ placed at the two ends of an insulating rod of length $d$ and negligible mass. Write down the dipole moment. Is it a vector or a scalar? The dipole is then placed in a uniform electric field and is given a small angular displacement $\mathrm{\theta }$ from its equilibrium position. What are the total force and torque acting on it?

Define dielectric constant. What do you mean by the statement - dielectric constant of mica is $6$?

The mutual force of repulsion between two point charge having fixed distance between them is $9$ Dyne in vacuum and $4$ Dyne in a dielectric medium. What is the dielectric constant of the medium.

An electric dipole is held in a uniform electric field . By using suitable diagram, show that it does not undergo any translatory motion.