Lenz's law

Lenz's law


Lenz's law is a way of understanding how electromagnetic circuits obey Newton's third law and the conservation of energy. Lenz's law is named after Heinrich Lenz, and it says:


An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.
or
The Induced current is such as to oppose the change in applied field
Lenz's Law is all about conservation of energy. It guarantees that induced currents get their energy from the effect creating the change. The force acting against the conductor being moved earlier is actually an invocation of Lenz's Law. ( As the conductor moves down, the flux increases, so the induced field opposes this which leads to the direction of the Induced current - which in turn shows the direction of the force back on the current.)

History


Heinrich Friedrich Emil Lenz
Lenz's law, was discovered by the Russian scientist H. F. E. Lenz in 1834, that states that the electromotive force (emf) induced in a conductor moving perpendicular to a magnetic field tends to oppose that motion.

He is most noted for formulating Lenz's law in electrodynamics in 1833. The symbol L, conventionally representing inductance, is chosen in his honor.


Lenz had begun studying electromagnetism in 1831. Besides the law named in his honor, Lenz also independently discovered Joule's law in 1842; to honor his efforts on the problem, it is also given the name the "Joule–Lenz law," named also for James Prescott Joule.



Explanation Of Lenz's law


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.


References

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