Induction, Electric

Induction, Electric, is the process by which an electrically charged object charges another object without touching it. It is caused by electrostatic attraction, the attraction that opposite electrical charges have for each other. Electrostatic attraction differs from electromagnetic induction, the force produced on an electrically charged particle by a changing magnetic field.

Electric induction can be used to charge a metal object supported by an insulator. For example, a glass rod rubbed with silk will become positively charged. If it is brought near--but does not touch--the insulated metal object, the rod pulls electrons in the metal to the side of the object nearest the rod. The opposite side of the object then lacks electrons. If the opposite side is momentarily connected to the ground, electrons will flow into the object and neutralize the positive charge on that side. After the ground connection and the glass rod are removed, the metal object retains the excess negative charge it received by induction.

The Van de Graaff generator is a machine that uses electric induction. In it, a moving insulating belt charges a hollow metal dome to many million volts. This high voltage is used to accelerate charged particles used in nuclear physics experiments.

Contributor: Lynn W. Hart, Ph.D., Physicist, Principal Staff, The Johns Hopkins Univ. Applied Physics Laboratory.

Induction, Electric

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