Question

explain why the capacitance of a parallel plate capacitor increase when a dielectric slab is introduced between the plates​

Answer 1

Any medium which is placed between the plates of parallel plate capacitor is known as dielectric. Dielectric increases the capacitance of capacitor.

Inside the dielectric the atoms and electrons create a dipole which opposes the movement of charges from the planets of capacitor , due to which charges remain attached with the plates of capacitor and its capacitance increases.