Lenz's Law

Lenz's law, pronounced LEHN zuhz, is a principle of physics important in the design of electric generators. It was developed by Heinrich F. E. Lenz, a German-born scientist. Lenz's law describes the direction of flow of an electric current generated in a loop of wire when an external magnetic field passes through the loop. The current creates its own magnetic field. Lenz's law states that the current will flow around the loop in a direction such that its own field will oppose any change in the external magnetic field. Variations in the total magnetic field through the loop are thereby kept to a minimum. This means that work must be done to generate electricity. Thus, powerful turbines are needed to run generators that supply large amounts of current. But an external magnetic field can also be used as a "brake" to slow down an electric generating mechanism.

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

Lenz's Law

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