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| Invention Directory > Electricity & Electronics > Inventions > Lenz's Law |
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Lenz's law gives the direction of the induced emf (electromotive force) resulting from electromagnetic induction, thus: The emf induced in an electric circuit always acts in such a direction that the current it drives around a closed circuit produces a magnetic field which opposes the change in magnetic flux which produces the emf. For Example, when an electric motor is in operation, the armature is turning in a magnetic field, and an emf is thus induced in it. Lenz's law requires that this emf, called back emf or counter emf, oppose the motion of the armature and also the original emf, causing the motor to operate. As a result, the speed of the motor changes in such a way that the energy supplied by the original voltage source less the energy required to overcome the back emf is always exactly equal to the sum of the energy used to drive the mechanism to which the motor is attached and the energy lost as heat within the motor. Lenz's law may thus be seen as a consequence of the law of conservation of energy. The law is named after the Physicist Heinrich Lenz, who formulated it in 1834. See Maxwell's equations for further mathematical treatment.
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