Question

A slab X is placed between the two parallel isolated charged plates as shown in the figure. If $E_p$ and $E_q$ denotes the intensity of electric field at P and Q, then :

• A. $E_p$ is reduced by the presence of X, if X is metallic
• B. $E_q$ is increased by presence of X, if X is dielectric
• C. $E_q$ is in the opposite sense to $E_p$, if X is dielectric
• D. $E_q$ is zero, if X is metallic

Answer 1

The correct option is D $E_q$ is zero, if X is metallic

There is no effect of the metal on the external electric field(thus A is incorrect) while the dielectric reduces the net electric field outside. The dielectric produces an electric field inside it due to the induced charges which is opposite to the external field. Thus $E_Q$ is reduced and B and C are also incorrect.(Note that $E_P$ is not the external field). Now as the electric field inside the conductor is zero, the field $E_p$ is zero if X is a metallic. Thus D is correct.