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Lenz’s law of electromagnetic induction tells us that the changing magnetic field induces a current in the inductor such that the magnetic field created by the induced current opposes the initial changing magnetic field. We can find this current flow’s direction with the help of Fleming’s right-hand thumb rule.
Lenz’s law predominantly relies upon Faraday’s law of electromagnetic induction since Faraday’s law expresses that a differing attractive field will invite a flow of current into an electric coil. On the other hand, Lenz’s law expresses that the induced current flow opposes the early changing magnetic field which produced it. Hence, in Faraday’s law, the equation is through the negative sign.
ϵ = – dΦ/dt
Lenz’s Law and Law of Energy Conservation
Lenz’s law is considered a direct derivative of the law of conservation of energy. According to this law, the direction of the current induced via Lenz’s law creates a magnetic field opposing the magnetic field that created it.
Let us consider a scenario where this is not the case. Let the magnetic field created by the induced current be in the same direction as the field that produced it. This would result in these two fields combining and creating a larger magnetic field. The combined magnetic field would then induce double the amount of current within the conductor.
Hence, creating a magnetic field, which again induces another current and leads to an infinite positive feedback loop, violates the law of energy conservation.
This law also follows Newton’s third law of motion (there is always an equal and opposite reaction to every action). Therefore, if the induced current produces a magnetic field that is equal and opposite to the direction of the magnetic field, it can only resist the changing magnetic field in the environment.
Restrictions on Lenz’s Law
The limitations of Lenz’s law are as follows:
When a magnet moves towards the coil, the external magnetic field will actuate a current inside the loop to make a magnetic field inside through a comparative magnitude. However, this will be from the opposite direction, thus restricting the change.
When the magnet travels through the coil or any other face of the loop, the progression of the current will adjust the course. The inside magnetic field will be enhanced in a similar direction due to the external magnetic field, again opposing the change.
Application of Lenz’s Law in Physics
The application of Lenz’s law in physics is as follows:
Lenz’s law helps us understand the concept of magnetic energy stored in inductors. When we connect the electromotive force (EMF) source to both ends of the inductor, current begins to flow through the inductor. As a result, the EMF counter cancels out this increase in the flowing current through the inductance. Hence, to establish the current flow, the external EMF source needs to do some work to get over this resistance. This can be done by storing the EMF in the inductor, so that it can be restored after removing the external source of the EMF from the circuit.
This law shows that the induced EMF and the flux change have opposite signs and provides a physical interpretation of the sign selection in Faraday’s induction method.
Lenz’s law also applies to generators. When a current is induced in the generator, the direction of this induced current rotates the generator against the generator. Therefore, the generator requires more mechanical energy. Electric motors also provide back EMF.
Lenz’s law is also used in electromagnetic brakes and inductive cooktops.
The application of Lenz’s law in physics can also be seen in AC generators and electric generators
To see where Lenz’s Law is used in physics, we would need to take a look at the metal detectors and braking system of the train along with the microphones and card readers.
The application of Lenz’s law in physics can also be seen in the form of Eddy’s current dynamometers.
Conclusion
Lenz’s law predominantly relies upon Faraday’s law of electromagnetic induction since Faraday’s law expresses that a differing attractive field will invite a flow of current into an electric coil. Lenz’s law helps us understand the concept of magnetic energy stored in inductors. When we connect the electromotive force (EMF) source to both ends of the inductor, current begins to flow through the inductor. As a result, the EMF counter cancels out this increase in the flowing current through the inductance.
