The discovery and understanding of electromagnetic induction are based on a long series of experiment carried out by Faraday.Description of michael faraday experimentsExperiment 1: When a coil connected to a galvanometer G.
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When the North pole of a bar magnate is pushed towards the coil, the pointer in the galvanometer deflects, indicating the presence of electric current in the coil. The deflection lasts as long as the bar magnate is in motion. The galvanometer does not show any reflection when the magnate is held stationary. When the magnate is pulled from the coil the galvanometer shows deflection in the opposite direction, which indicate reversal of the current direction.
Moreover when the south pole of the bar magnate is moved towards or away from the coil the deflection in the galvanometer are opposite to that observed with the north pole for similar movement. Further, the deflection is found to be larger when the magnate is pushed towards or pulled away from the coil faster. Instead when the bar magnate is held fixed and the coil is moved towards or away from the magnate the same effect are observed.
It shows that it is the relative motion between the magnate and the coil that is responsible for generation of electric current in the coil.Experiment 2: In this the bar magnate is replaced by a second coil connected to a battery. The steady current in the coil produces a steady magnetic field as another coil is moved towards the first coil, the galvanometer shows a deflection.
This indicate that electric current is induced in the first coil. When the second coil is moved away, the galvanometer shows a deflection again, but this time in the opposite direction. The deflection lasts as long as the second coil is in motion. When the second coil is held fixed and the first coil is moved, the same effects are observed. Again, it is the relative motion between the coils that induces the electric current.michael faraday experiments
Experiment 3: The above two experiment involved relative motion between a magnet and a coil and between two coils respectively. Through another experiment, Faraday showed that this relative motion is not absolute requirement. In this two coils held stationary. The first coil is connected to the galvanometer while the second coil is connected to a battery through a taping key. It is observed that the galvanometer shows a momentary deflection when the taping key is pressed.
The pointer in the galvanometer returns to zero immediately. If the key is held pressed continuously, there is no deflection in the galvanometer. When the key is released, a momentary deflection is observed again, but in the opposite direction. It is also observed that the deflection increases dramatically when iron rod is inserted into the coils along with their axis.