ELECTROMAGNETISM (X CBSE Physics)

ELECTROMAGNETISM

The discovery of the relationship between magnetism and electricity was, like so many other scientific discoveries, stumbled upon almost by accident. The Danish physicist Hans Christian Oersted was lecturing one day in 1820 on the possibility of electricity and magnetism being related to one another, and in the process demonstrated it conclusively by experiment in front of his whole class! By passing an electric current through a metal wire suspended above a magnetic compass, Oersted was able to produce a definite motion of the compass needle in response to the current i.e. a compass needle got deflected when an electric current passed through a metallic wire placed nearby. If the direction of current in the wire is reversed, Then the direction of deflection of the needle is reversed. What began as conjecture at the start of the class session was confirmed as fact at the end. Needless to say, Oersted had to revise his lecture notes for future classes! His discovery  is the way for a whole new branch of science: electromagnetics.

His research later created technologies such as the radio, television and fiber optics. The unit of magnetic field strength is named the Oersted in his honor.

On passing the current through the copper wire XY in the circuit, the compass needle which is placed near the conductor gets deflected. If we reverse the direction of current by changing the polarity of battery, the compass needle deflects in reverse direction. If we stop the flow of current, the needle comes at rest. Hence, it concludes that electricity and magnetism are linked to each other. It shows that whenever electric current flows through a conductor, a magnetic field is created around the conductor. This phenomenon is called magnetic effect of electric current.

The relative strength and direction of magnetic field due to a conductor depends on the direction of electric current and shape of the current carrying conductor. When a magnet is placed in an electric field, it experiences some force. Similarly, when a current carrying conductor is placed in a magnetic field, it experiences some force. The interaction of these forces results in various phenomena. Many electrical gadgets work on some or other of these phenomena. Electric motor and electric generator are key devices which work on electromagnetism.