Monday, June 4, 2012

What is Electromagnetism?

            In 1820, Hans Christian’s Oersted of the University of Copenhagen observed that a compass gets deflected when placed near a wire, and electricity is passed through it. It also returns to its normal position when the current is switched off. It made Oersted realize that electric current produced magnetic effects. The relationship between magnetism and electricity was established in later years and the study of electricity and magnetism came to be known as electromagnetism.

An Electromagnet

            Subsequently, Michael faraday carried out further studies in the field of electromagnetism. The current passing through a wire produced a magnetic field, and this magnetic property was harnessed to produce motion in electric motors. But faraday went a step further- if a current can create a magnetic field, then ca a magnet produce electric current, he asked himself.

            Faraday discovered that it was not the magnetic field that created the current in a wire, but the movement of magnetic lines of force across the wire that produced the current. When a magnet, either an electromagnet or a permanent magnet, is moved ear an electrical conductor, turbulent current are induced in the conductor, which move around it. The conductor experiences a dragging force and electricity is induced in it. This force is regulated to produce an electric current like in a dynamo.

            A more complex example of electromagnetism is found in transformers where a changing magnetic field produces current. Here tow coils of wire are placed close to each other and an alternating current is passed through one coil, a changing magnetic field is produced which induces an alternating current I the second coil.

            Electromagnets are used in telephone ad electric bells. In scrap yards, powerful electromagnetic devices are used to separate iron and steel scraps from accumulated junk in steel and iron plants.