Lenz’a law and Conservation of energy

In this article, we will introduce Lenz law and conservation of energy from physics notes of chapter 6 electromagnetic induction. Here, we will discuss Lenz’s law, it’s formula, application, and Lenz’s law experiment done by Lenz.

This article will also help you to understand the basics of Lenz law and conservation of energy, the Faraday law conservation of energy and  Lenz’s law in accordance with the law of conservation of energy.

Electromagnetic induction is an important chapter in physics and  Lenz’s law and  conservation of energy is an important topic that falls under the chapter. Let’s dig into this chapter about the Lenz law and Conservation of energy.

About Lenz law and conservation of energy

“The polarity of induced emf is such that it tends to produce a current which opposes the change in magnetic flux that produced it”   

..statement by the Lenz’s law

Lenz’s law relies on Newton’s third law: the law of action and reaction and the principle of conservation of energy. It is the most useful method to deduce the path of the induced current. Heinrich Friedrich Lenz was a German physicist, who theorized a rule also known as Lenz’s law in 1835 which provides the polarity of the induced electromotive force clearly and concisely. Lenz’s law was named after Emil Lenz.

The induced emf with varied polarities induces a current whose magnetic field rejects the difference in magnetic flux through the loop to assure that initial flux is conserved through the loop when current cycles in it.

Lenz law notes that when the magnetic flux is boosted through a sealed loop, a current is induced which rejects the rate of change of flux or the reason that generates it. This implies that Lenz’s law is in accordance with the law of conservation of energy.

Faraday law conservation of energy: according to the law, whenever there is an alteration in the magnetic flux, an electromotive force is generated, as a result, there will be elicited current.

Lenz’s law and conservation of energy: according to the law, the direction of the elicited current will be such that it rejects the difference in the magnetic fluctuation.

Lenz’s law assists conservation of energy

• Lenz’s law fulfills the conservation of energy.
• A magnet is moving and as a result a current is being induced and when the magnet is not moving there is no induced current in the coil.
• There is mechanical energy implicated with the activity of the magnet resulting in mechanical energy being recycled into electrical energy which is elicited by the induced current.
• Magnetic energy utilized in moving magnets is getting transformed into electrical energy which is obtained by the induced current.
• This shows that Lenz’s law favors the conservation of energy where one form of energy is getting transformed into another form.
• Work done in moving the magnet is given by joule heating obtained by the induced current.

The formula of Lenz’s law

Lenz’s law is indicated in the formula of Faraday’s law. Here the -ve sign is allotted from Lenz’s law. the expression is :

Emf = −n(δϕ/δt)

where electromotive force is the induced voltage (also known as emf)

n = the no. of loops.

δϕ is change in magnetic flux

δt is a change in time.

Application of Lenz’s law

There are many applications of Lenz’s law. some of the applications are as follows:

Microphones, AC generator, metal detectors, the braking system on train, card readers, eddy current balances and eddy current dynamometer.

Lenz’s law experiment

We would like to use Lenz’s law to find the direction of the induced emf and current. some of the experiments that were proved by Lenz’s following his theory are as follows: 

First experiment: Lenz deduced that when the current in the coil streams in the circuit the magnetic field lines are generated. As the value of current flowing through the coil increases, the magnetic flux also increases. 

Second experiment: When the current carrying coil is wound on an iron pole such that its left end behaves like the north pole of a magnet and then it is moved towards another coil P, then a current is induced in P.  

Third experiment: Lenz surmised that when the coil is forced towards the magnetic flux, the surface of the coil inside the magnetic field goes on decreasing. According to Lenz’s law, the movement of the coil is opposed when the induced current is applied in the same direction.

To generate current, force is put forth by the magnet in the coil. To oppose the change a force must be put forth by the current on the magnet. 

Conclusion

Lenz’s law is in accordance with the law of conservation of energy and Newton’s third law. Its formula is derived from the Faraday law conservation of energy; the negative sign in the formula is given from Lenz’s law. Lenz’s law is applied to many things like an ac generator.