The magnetic effects of electric current were first discovered by Hans Christian Oersted, a Danish physicist. Oersted, in 1820, discovered that a compass is deflected when an electric current is passed through a wire kept nearby. He initially postulated that magnetism radiates from all sides of the wire. However, after more experiments he concluded that electric current produces circular magnetics fields.
In the previous article on magnetism, we had performed an activity where we sprinkled iron filings over a sheet. What happens when the electric current passes through the wire? The iron filing organises themselves along the circular magnetic fields produced by the magnetic effects of electric current.
Let us do some more activities to understand the relationship between electricity and magnetism.
We will need a straight copper wire, two or three cells and a plug key. We will first connect these in a series so that the copper wire is directed along the north-south axis. Next, we will place a compass over the copper wire, keeping the needle parallel to the copper wire. Now, what happens when current is passed through the copper wire? The compass needle deflects. Now, what happens when the direction of the current is changed? The direction of the deflection of the needle is in the opposite direction. Why does this happen?
The change in the direction of deflection can be explained by the right-hand thumb rule. Imagine that you are holding the current carrying wire in your hand in such a manner that the thumb points towards the direction of the current and the fingers are wrapped around the wire. The direction of the fingers would depict the direction of the magnetic fields.
Now, let us get back to our activity. We will modify our experiment to include a rheostat to control the flow of the current. What happens when we increase or decrease the flow of current through the wire? We will note that the deflection of the compass increases progressively as the strength of the current increases. Thus, the magnetic effects of electric current are directly proportional to the force of the current.
What happens when the compass is moved away from the copper wire? We will note that the deflection of the compass progressively decreases when the compass is moved away from the copper wire. Therefore, we can conclude that the magnetic effects of electric current reduce in intensity as we move farther away from the current-carrying wire.
So what have we learnt about the magnetic effects of electric current in this article?
- An electric current passing through a conductor produces a circular magnetic field around the wire.
- The direction of the magnetic field can be deduced by the right-hand thumb rule.
- The strength of the magnetic field increases when the force of the current passing through the conductor.
- The strength of the magnetic field decreases as we move away from the centre of the conducting core.