Explain briefly, using a paper diagram, the difference in behaviour of a conductor and a dielectric in the presence of an external electric field.

(a) When a conductor is placed in an electric field, charge distribution takes place. This distribution is such that the electric field is zero inside the conductor (that is after the charge is distributed and reached a stable state). The electric field due to the induced charge cancels the external field. (Ref image 1)
When a dielectric is placed in the external electric field, an induced electric field appears in the dielectric in the opposite direction of the external electric field, having the magnitude E0k as the net field (Refer image 2)