What is Polarization of Dielectric Material?

Polarization of Dielectric Material: Consider a parallel plate capacitor with +q and –q charges.

Fig: Polarization of dielectric material

Let E₀ be the electric field between the plates in the air. If a dielectric slab is introduced in the space between them, the dielectric slab gets polarized. Suppose +q_i and –q₁ be the induced surface charges on the face of dielectric opposite to the plates of the capacitor (Figure). These induced charges produce their own field E_i which opposes the electric field E₀. So, the resultant field, E < E₀. But the direction of E is in the direction of E₀.

so, E = E₀ + (–E_i)

(Here E₁ is opposite to the direction of E₀)