Hawkins Electrical Guide v. 01 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

Hysteresis.—The term hysteresis has been given by Ewing to the subject of lag of magnetic effects behind their causes. Hysteresis means to “lag behind,” hence its application to denote the lagging of magnetism, in a magnetic metal, behind the magnetizing flux which produces it.

Ques. What is the cause of hysteresis?

Ans. It is due to the friction between the molecules of iron or other magnetic substance which requires an expenditure of energy to change their positions.

Ques. When do the molecules change their positions?

Ans. Both in the process of magnetization and demagnetization.

Ques. What becomes of the loss of energy due to hysteresis?

Ans. It is converted into heat in changing the positions of the molecules during magnetization and demagnetization.

Ewing gives the value for the energy in ergs dissipated per cubic centimetre, for a complete cycle of doubly reversed strong magnetization for a number of substances as follows: