What is electromagnetic induction?
Previously, we have learnt about the relation between magnetism and electric current. We have learnt that when a current carrying conductor is placed in a magnetic field, it experiences a force. What would happen if this conductor were moving or if the strength or direction of the magnetic field were to change? Michael Faraday, an English scientist, studied these problems initially and in 1831, postulated the principles of electromagnetic induction. Electromagnetic induction refers to the production of an electromotive force across a conductor exposed to varying amounts of magnetic fields.
Let us now do a small experiment to answer a few questions.
Take a coil of a vast number of turns. We will label one end of the coil as A and another end as B. Connect the two ends of the coil to a galvanometer. Now, take an active magnet and move the north pole of the magnet into the coil, towards the B end of the loop. What do you note?
You will see that there is a momentary deflection of the galvanometer. Now, reverse the magnet and move the south pole of the magnet towards the B end of the coil. What do you note? You will note a deflection in the galvanometer. But, this time, the direction of the deflection would be opposite to the previous deflection. Therefore, we can conclude that movement of a magnet in respect of the coil induces the production of a current in the coil. Similar results can be got by moving the coil instead of the magnet.
Now let us set up another experiment.
Take two turns of coils. Let us name these coils as A and B. The coil?A and B will need to have a different number of turns. For the purpose of the experiment, we shall assume that coil A has 100 turns and coil B has 50 turns.We will also need a battery, one galvanometer and a core of non-conducting material (a paper or cardboard core).We will set up the equipment in such a way that both coil A and B are wound over the non-conducting core and are a few centimetres away from each other. We will now connect coil A to a battery and coil B to a galvanometer. What would happen when current flows through coil A?
We will note a momentary deflection of the galvanometer. Now, disconnect the battery from coil A. You will note another momentary deflection of the galvanometer. However, this time, the direction of deflection would be opposite to the previous instance. Can you explain the results of the above experiment?
We have previously learnt that when current passes through a conductor, it produces a magnetic field around the wire. In the above experiment, as the current across coil A varies, the magnetic field around coil A also changes. The change in the magnetic field around coil A leads to a change in the magnetic field around coil B as well. Any change in the magnetic field around a conductor will induce production of a potential difference in the conductor and this leads to setting up of an electric current within the conductor.
The above experiments are simple demonstrations of the principle of electromagnetic induction.
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