Question

What is the Lenz's law and conservation of energy Class 12?

Answer 1

Lenz's Law is a fundamental principle in electromagnetism that describes the direction of an induced current in a conductor when it is exposed to a changing magnetic field. It is closely related to Faraday's Law of Induction and also helps explain how energy is conserved in electromagnetic systems.

Lenz’s Law

Lenz's Law states that:

“The direction of the induced current in a conductor is such that it opposes the change in magnetic flux that caused it.”

In simpler words, when a magnetic field changes near a conductor (like a coil or loop of wire), it induces a current in the conductor. The direction of this current will be such that it creates its own magnetic field that opposes the original change in the magnetic field.

This opposition helps to conserve energy and prevent the system from creating energy out of nothing.

Example to Understand Lenz's Law:

Imagine you have a coil of wire and a magnet. If you move the magnet towards the coil, the changing magnetic field induces a current in the coil. According to Lenz's Law, the direction of the induced current will be such that the magnetic field created by this current will try to oppose the magnet's motion (the change in magnetic flux).

1. If you move the magnet towards the coil, the induced current creates a magnetic field that repels the magnet.
   

1. If you move the magnet away from the coil, the induced current will try to pull the magnet back by attracting it.
   

This opposition is the key to energy conservation.

Conservation of Energy in Lenz's Law:

Lenz's Law is also a reflection of the conservation of energy principle. Here’s why:

1. When a magnet moves towards or away from a coil, it changes the magnetic flux in the coil.
   

1. The induced current produces its own magnetic field, which resists the motion of the magnet.
   

1. To move the magnet, work must be done against the magnetic field of the induced current. This work corresponds to the energy supplied to move the magnet, and it shows that no energy is created or destroyed; it is just transferred from one form to another (like mechanical energy to electrical energy and vice versa).
   

If Lenz’s Law did not hold, it would be possible to generate energy without any external work (perpetual motion), which would violate the principle of conservation of energy.

Summary:

1. Lenz’s Law ensures that the induced current always works to oppose the change in the magnetic flux.
   

1. This opposition ensures the conservation of energy because it prevents the creation of energy from nothing and requires work to change the magnetic flux.
   

In conclusion, Lenz's Law is an essential concept for understanding how energy is conserved in electromagnetic systems and ensures that the laws of physics, including energy conservation, are not violated.