- The flow of current lasts as long as the change takes place. - This phenomenon is called Electromagnetic induction.
-We know that when current is passed through a conductor, it behaves like a magnet, in other words a magnetic field is created around it. - Can the reverse take place?
Explanation
Can electric current be obtained from a magnetic field?- This concept was successfully discovered by the British Scientist Micheal Faraday in 1831.
- Take a cylindrical coil with many turns.- Connect it to a galvanometer and place a magnet along the axis of the cylindrical coil.
Let us study a simple experiment to understand this :
- When the magnet is stationary, there is no deflection in the galvanometer. - This indicates no current flows through the coil.
Figure 1
- When the north pole of the magnet is brought near the coil the current flows in the coil and the galvanometer deflects towards the right.
Figure 2
- As soon as the motion of the bar magnet is stopped , the galvanometer comes to zero position.- Indicating that there is no flow of current.
Figure 3
- Now take away the north pole of the magnet from the coil. - The galvanometer deflects towards left, indicating that the direction of flow of current is opposite to that in figure 2.
Figure 4
- If the south pole of the magnet is brought near the coil, the galvanometer deflects towards left, indicating that the direction of flow of current is opposite to that in figure 2.
Figure 5
- Same results can be obtained by fixing the bar magnet and moving the coil. - So whenever there is a relative motion between the coil and the bar magnet, electric current is induced in the coil.
- The relative motion between the magnet and coil brings about a change in magnetic field lines entering the coil.
The devices that work with electromagnetic induction are generators and transformers.