Lenz's Law in 3D Animation. Lenz Law. Class 12 Physics. NEET, JEE MAIN.
Class 10 Physics
Class 12 Physics
Electromagnetic Induction
If you move an electric loop, or a solenoid, near a magnet, an instantaneous potential difference, or, an instantaneous electric current generates, throughout the loop, or solenoid.
The incident is called electromagnetic induction. You can measure the amount of current by using Faraday's law of electromagnetic induction. But, what about the direction of the induced current?
Lenz's law has its answers.
So, what is Lenz's law? It says, the direction of the induced electric current should be, in such a way, that it opposes the cause of its generation.
Have you understood these lines ?
Well, here is the explanation.
When a solenoid move about a magnet, four possible situations may arise.
Let us view them, one by one. In the first situation, say the solenoid approaches the north pole of the magnet.
In our second situation, the solenoid moves away from the north pole of the magnet.
In the third scenario, let the solenoid approaching to the south pole of the magnet.
And, in the fourth and last scenario, the solenoid moving away from the south pole of the magnet.
Before going further, let us check the positions of the north pole and the south pole in a solenoid, when current flows through it.
Normally, a solenoid is a non-magnetic object.
When an electric current flows through it, it starts behaving like a magnet. In a current carrying solenoid, from one end of the solenoid, the current may appear to be revolved, in an anticlockwise direction. And, from the other end, the current should be in clockwise rotation. The side from which, the current is anticlockwise, is the north pole of the solenoid. And, the side, from which the current is clockwise, there is the south pole of the solenoid.
Okey. We have learnt the pole position.
Now, review the statement of the law again.
Here, a question arises. What is the cause, that generates the induced current?
And, its answer is, The movement of the solenoid.
So, the induced current should oppose the movement of the solenoid.
How it works? How come it oppose the movement of the solenoid.
Let us see, the first situation.
Here, the solenoid is approaching the north pole. It is the cause of the induction. And the law says, the induced current will resist its movement, towards the magnet. How come it do so?
It will produce a North pole near the permanent magnet. So that, the magnetic north pole can repel the north pole of the solenoid. To produce a North pole, it need to generate a current, in anticlockwise direction. Hence, the cause, the advancement of the solenoid, will be denied. And thus, the direction of the current current is anticlockwise.
Now, check the second situation. Here, the cause of generation of the induced current, is the retreat of the solenoid. To conter its movement, an attraction force should arise between the magnet and the solenoid. To do so, the solenoid should create a south pole, near the magnet. And, to produce a south pole, it should generate a clockwise current. Hence, the current should be clockwise, in this occasion.
Take the third scenario. Here, the cause of generation of the induced current, is the advancement of the solenoid, towards the south pole of the magnet. To counter its advancement, a repulsive force need to be generated. To get a repulsion, the solenoid should produce a south pole, near the magnet. Hence, the direction of the induced current, in the solenoid, is clockwise.
Now, it is a question for you. What should be the direction of the induced current, in our fourth and final scenario? And why?
Hope you realized the topic. Answer the questions, if you understood this topic.
Lenz's law, actually, is a special form of the law of conservation of energy. If, say, the electromagnetic induction does not follow the lenz's law. Then, what could be happened there?
The solenoid and the magnet, then, could produce enormous electric energy, from a small amount of mechanical energy. Which is impossible. As per the law of conservation of energy.
