What is Lenz law?
Lenz’s law states that the direction of the electric current induced in a conductor by an external changing magnetic field is such that the magnetic field created by the induced current opposes changes in the external magnetic field. The direction of the induced current can be derived from Fleming right hand thumb rule.
Direction of current using Lenz law
Using this law, one can predict the electric current’s direction induced by the external magnetic field. The magnitude of the electric current cannot be predicted.
In Faraday’s law of induction, Lenz’s law adds the negative sign.
$$E=-\cfrac{d\phi{}}{dt}$$
Faraday's law and Lenz law
Faraday’s law tells us the magnitude of the EMF produced but it does not say anything about the direction of EMF/Current produced. Lenz’s law tells us the direction the current will flow.
Lenz law and conservation of energy
Lenz’s Law is a manifestation of the conservation of energy principle. These are intertwined concepts in electromagnetism. It ensures that the energy used to change the magnetic flux is conserved. The work done to change the magnetic field is equal to the energy dissipated as electrical energy due to the induced current.
Application of Lenz law
Lenz’s Law is fundamental to the operation of generators, transformers, and many electrical devices. It tells the direction of the induced voltage.
It’s also the reason why, for example, when you drop a magnet through a coil, it induces a current that resists the motion of the magnet.