ELECTROSTATIC POTENTIAL AND CAPACITANCE — Physics STD 12 Science — Question

• Conductor in external electric field :
→ As shown in figure (a) when a conductor is placed in external electric field, static electric charge is induced on its surface. Electric field is created inside the conductor due to this electric charge.
→The electric field generated due to induced charges, opposes the external electric field in the region inside the conductor.
→In stable situation, both these electric fields cancel out their mutual effect. When both these electric fields are of equal magnitude the net electric field inside conductor vanishes to zero.
• Dielectric in the external electric field :
→Non-conducting material is called dielectric. Free motion of electric charges is not possible in dielectric.
→The external electric field induces dipole moment either by pulling the molecules of dielectric or by their re-arrangement. Due to which some net charge is induced on the surface of the dielectric.
→The electric field produced by this electric charge opposes the external electric field.
→Due to which electric field inside the dielectric decreases.
→In non-conducting materials, magnitudes of both these electric fields cannot be equal and hence net electric field inside die-electric is not zero.