Electrostatic induction

Electrostatic induction is a redistribution of electric charge in an object, caused by the influence of nearby charges, and a method to create or generate static electricity in a material by bringing an electrically charged object near it. This causes the electrical charges to be redistributed in the material, resulting in one side having an excess of either positive or negative charges. Electrostatic induction does not involve the objects touching, as it does in conduction. Electrostatic induction creates static electricity, where charges build up on an object but do not move.

The phenomenon of electrostatic induction is due to a property of electric charges: bipolarity, i.e. the fact that in nature there are charges of two different types, which conventionally are distinguished by a positive or negative sign, and by the fact that diversity of the sign of the charges generates attraction and in the case of concordance of the sign repulsion. Electrostatic induction is therefore based on the principle of charge redistribution, according to which a charged object, placed near a neutral conductor, is able to attract the opposite sign charges to itself and to reject those of the same sign. Thanks to this redistribution it is possible to create a partial charge of opposite sign to that of the inducing with consequent generation of an attractive force.

This phenomenon is most effective when the objects are conducting materials, such as metals. The only drawback is that once the electrically charged object is removed, the conductor loses its charge. This can be solved by temporarily grounding the conductor. Certain non-conducting materials can also be given a static electric charge by electrostatic induction. In these cases, it is caused by the polarization of their molecules.

Several electrostatic generators, such as the Wimshurst machine, the Van de Graaff generator and the electrophorus, are based on this principle.