Lenz's law Definition & Effects


Lenz's Law Definition

Lenz's law can easily be defined during a single sentence as below.

Lenz's law states that the present induced during a circuit thanks to a change or a motion in a very field of force is so directed on oppose the change that caused it.

Lenz's law is one in all the essential laws of electromagnetism. Wherever electromagnetism exists, its effects are going to be felt when any changes occur.
Lenz's law, created in 1834 by Russian physicist Heinrich Friedrich Emil Lenz. Lenz’s Law applies to self inductance because an induced current includes a direction specified its flux opposes the change in field that induced this.

Lenz's law also applies when there's physical motion, like that of a magnet.

Lenz's law effects

Lenz's law will be felt in many ways and in some it may be seen that the conservation of energy laws are obeyed as a result. Physical samples of its presence are often seen in an exceedingly form of ways.

Permanent magnet and coil

one amongst the best methods of demonstrating Lenz's law is to maneuver a permanent magnet into a coil. because the field from the magnet moves across the coil, an electrical current is induced. successively this current sets up a field round the coil making the coil an electromagnet.

Because like poles repel one another, Lenz's law enables us to predict that when the pole of the magnet is approaching the coil, the present induced is in such a direction, that the side of the coil nearest the North Pole of the magnet also becomes a pole and during this way it opposes the approaching magnet. When the magnet is withdrawn from the coil, the induced current reverses itself, in order that the side of the coil near the magnet North Pole becomes a South Pole to supply an attracting force on the magnet being removed.


Taking the magnet analogy further, it may be seen that turning a dynamo over will induce a current specified the movement of the dynamo is opposed. As a result, work should be done to show over the dynamo and generate current. during this way the energy put into turning the dynamo over, is converted into electricity and int his way the laws of the conservation of energy are preserved.

Slow build up in current in coil after switch on

in our own way within which Lenz's law makes its presence felt is when current during a circuit including an is tuned on. The fastest rate of change occurs just at start when an outsized jump in voltage is applied. A back EMF is constructed up, and as a result, the present within the circuit slowly builds up.

Inductance Current Time Graph

Back EMF generated in coil at turn off

Similarly when the present is turned off, Lenz's law comes onto play. The inductor opposes the change that has occurred when the circuit is broken and also the current is suddenly stopped. As a result an oversized back EMF is induced which tries to make sure the present continues to flow. This back EMF will be very large and may cause arcing at the switch contacts.

relay common emitter transistor drive circuit

Where circuits are controlled by a transistor or FET, the rear EMF can create to very large voltages that may destroy the device. to beat this a suppressor diode is included across the inductor coil - during this case that of a relay. this can be reverse biassed under normal operation, but when the rear EMF is generated, which is within the opposite sense thereto of the voltage under normal operating conditions, the diode starts to conduct, safely dissipating the rear EMF.

Impeding AC flow

Inductors impede the flow of electricity flow as a results of Lenz's law. this is often actually a awfully useful feature of inductors. According to this definition, electricity varies continuously.  And as a result of Lenz's law, a back EMF is constructed.  Thereby combating this flow as a result of Lenz's law. This voltage is proportional to the inductance and also the rate of change. during this way the induced voltage will work against the voltage causing the present to flow and during this way it'll impede the present flow.

Lenz's law is one among the essential laws related to inductors and inductance. it's at the core of understanding why inductors behave as they do: resisting any change, resisting the flow of AC, slowing the rise of current during a circuit. When electricity is generated by the dynamo.  So the EMF has to be returned, and the work done continuously. this implies the presence of Lenz's law is felt in many scenarios.

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