Lenz’s Law


Tells the conservation of energy and the direction of induce emf and direction of induce current.



Lenz’s Law states that the induce emf in the coil or circuit is such that it opposes the changes of magnetic flux that produced it.

 


 

1) When bar magnet is approaching towards the coil the coil produce an emf and induces a current such that the coil develops



North pole towards north pole of the magnet. This induction opposes the approach of the magnet.



 

2) When bar magnet leaving the coil, the coil induces an emf or current, such that a south pole is pointing towards the north pole of the magnet. This induce current attracts the bar magnet towards it.



And the direction of current in this scenario is reverse to the former case.



 

Q. Now question is why it happens:

This happens because of conservation of energy.

 



1) During the approach of north pole of magnet, if south pole is generated on the coil, then they will attract one another and no work has to be done.



2) In that case work will be done automatically, it is impossible to build a machine that it work automatically and it will fail the conservation of energy which is not possible.

 



3) North pole generates when north pole is approaching means work has to be done by external agency. This work done generates electricity in the coil.

 



4) South pole generates in the coil when north pole is leaving means work has to be done by external agency against the force of attraction. This external work develops electricity in the coil.