All of us know that whenever an electric current flows through a conductor, a magnetic field appears surrounding the conductor. Again the electric current means the flow of electrons. Hence, the motion of electrons causes the magnetic field. The opposite is also true. That means a changing magnetic field linking to an electric conductor, produces a flow of electrons in the conductor.
In other words, whenever a changing magnetic field links with a conductor, it induces an electric current in the conductor provided the conductor is the part of a closed circuit. If the conductor is open, changing magnetic field induces only an emf across the conductor. More precisely we can say whenever a changing magnetic flux links with a conductor or in other words a conductor cuts the changing magnetic flux; an emf is induced in the conductor. We call this phenomenon as electromagnetic induction. Therefore this is the relation between magnetism and electricity.
Invention of Electricity from Magnetism
Scientist Hans Christian Oersted first discovered that an electric current produces a magnetic field surrounding it.
From that time different scientists also tried to search for a reverse phenomenon. That means the production of current due to a magnetic field. But among them, Michael Faraday succeeded to produce electricity from magnetism. He did this with continuous researches and experiments for long nine years. In the year 1831, he published his famous laws of electromagnetic induction. Electromagnetic induction is the phenomenon by which he had produce electricity from magnetism. We know his famous laws as Farad’s law of Electromagnetic Induction.
Production of EMF and Current from Magnetism
Let us connect one galvanometer in between two terminals of a simple coil. Now we place the coil in close vicinity of a permanent magnet. Obviously some flux of the magnet links with the coil. But there would not be any deflection in the pointer of the galvanometer. That means there is no current flow in the coil.
Now, let us bring the magnet quickly to the more closed position of the coil. Then we see that there is a momentary deflection in the pointer of the galvanometer. Again the deflection lasts as long as the magnet moves.
When the magnet reaches its destination, deflection of the galvanometer again becomes zero. So, we have observed that there is a current in the coil only when the magnet is in the moving condition. That means the coil produces current only when the flux linkage with it, changes. When we bring the magnet from its far position to the closed position to the coil, the flux linkage with the coil increases accordingly.
Now we bring back the magnet to a far position. Here also the pointer of the galvanometer deflects as long as there is a motion in the magnet. But the deflection of the pointer is opposite of that of the previous case. Obviously here during shifting the magnetic away from the coil the flux linkage decreases.
The deflection of the pointer of the galvanometer indicates the production of emf in the coil. And this e.m.f exists as long as there is a changing flux linkage with the coil.
Production of Current in a Conductor Moving in the Magnetic Field
So far we have experimented the phenomenon of electromagnetic induction with a coil. But it is also true that when a single conductor moves in a magnetic field, it also carries current due to electromagnetic induction. Suppose there is a conductor AB. This is the part of a closed circuit. The circuit is closed by connecting galvanometer as shown.
Now we move the conductor AB in between the north and the south pole of a magnet. Hence the conductor cuts the magnetic flux lines from the north pole to the south pole of the magnet. Therefore an emf is induced across the conductor AB. Due to this emf, a current starts flowing through the galvanometer. Therefore the pointer of the galvanometer deflects.
The magnitude of the deflection of the galvanometer depends on the speed of the motion of the conductor in the magnetic field. In other words, the magnitude of deflection of the galvanometer pointer increases when we move the conductor faster in the field. Again the magnitude of the deflection decreases when we move the conductor slower. The direction of the deflection of the pointer also depends on the direction of the motion of the conductor in the field. Flaming’s right-hand rule tells us the relation between the direction of the magnetic field, induced e.m.f or current and motion.
This was a brief description of the relationship between magnetism and electricity.