October 25, 2023

If N be the number of molecules per unit volume and α the molecular polarizability then Total polarization [latex] \quad \mathrm{P}=\mathrm{N} \alpha \mathrm{E}_{\mathrm{int}} [/latex] eqn, (10) [latex] \therefore \quad E_{\text {int }}=\frac{\mathrm{P}}{\mathrm{N} \alpha} [/latex] Further, we know that [latex] \begin{aligned} \mathrm{D} & =\varepsilon \mathrm{E}=\varepsilon_{0} \mathrm{E}+\mathrm{P} \\ \left(\varepsilon-\varepsilon_{0}\right) \mathrm{E} & =\mathrm{P} \\ \mathrm{E} & =\frac{\mathrm{P}}{\varepsilon-\varepsilon_{0}} \end{aligned} [/latex]

When a dielectric material is placed in an external electric field, it exerts a dipole moment in it. The total electric field at the atom site of the dielectric kept in an applied electric field is called the internal field. It is given by the sum of the applied field (E) and the electric fields