The molecules of many dielectrics possess an electric dipole moment without having an external electric field. In such molecules centres of their positive and negative charges are displaced with respect to each other and therefore form a dipole. Such materials are known as polar materials. These dipoles are oriented in a random fashion in the absence of an electric field. Under the influence of an electric field these dipoles orient themselves in the direction of applied. The stronger the field the greater will be the number of dipoles pointing in the direction of the field.