Chapter-6|Electromagnetic Induction (EMI)| NCERT 12th Physics:
Experiments of Faraday and Henry on EMI:
It is the relative motion between the magnet and closed coil which is responsible for generation of induction of electric current in the coil.
First Experiment(Current Induced by Magnet):
In this experiment, we consider a coil C of few turns of conducting material insulated from one another and it is connected to a sensitive galvanometer.
Whenever there is a relative motion between the coil and magnet the Galvanometer shows a deflection indicating that current is induced in the coil.
The above experiment shows that due to change in magnetic flux, a current is generated in the coil called induced current.
Second Experiment(Current Induced by Current):
When a bar magnet is replaced by a second coil C₂, connected to a battery, the steady current in coin C₂ produces a steady magnetic field. As coil C₂ is moved towards coil C₁, the Galvanometer shows a deflection. This indicate that electric current is induced in coil C₁.
Third Experiment(Current Induced by Changing Current):
In this experiment two coil C₁ and C₂ held stationary. Coil C₁ is connected to a galvanometer G, while the second coil C₂ is connected to a battery through a tapping key K.
It is observed that the Galvanometer shows a momentary deflection when the tapping key K is pressed. If the key is pressed continuously, there is no deflection in the Galvanometer. When the key is released, a momentary deflection is observed against but in opposite direction.
All experiment observation lead us to conclude that induced EMF appears in a coil, whenever the amount of magnetic flux linked with the coil changes.