Electromagnetic Induction

The intimate relationship between electricity and magnetism has been known for close to 200 years. In 1820, a scientist moved the needle of a magnetic compass with a wire that had an electrical current. That simple experiment illustrated the immensely useful concept that moving electrical charges create a magnetic field.

When it was later discovered that the opposite was also true--that a changing magnetic field produces an electrical current in a conductor, such as a wire-- electromagnetic induction was established. Both electrical charges and magnetism exhibit force fields. Although invisible, these force fields form loops known as lines of induction. These lines are imaginary, but they are the basis for the classic science class demonstration of a magnetic force field in which iron filings make patterns that follow the lines of induction.

Everyday Uses of Electromagnetic Induction

Once the reciprocal relationship between electricity and magnetism was established, practical applications were unending. The generator alone gave rise to a variety of industrial enterprises. By changing mechanical energy into electrical energy, the generator uses the principle of electromagnetic induction by passing an electrical conductor through a magnetic field. When one side of a coil passes through the magnetic field in one direction and then the other direction, alternating current results. Thus, the name of the alternator, as used in vehicles.

A transformer sends alternating current from one electric circuit to another by using electromagnet induction. Every neighborhood with electricity has a transformer on a nearby power pole. These power transformers are usually used to send power at a steady frequency. Radio frequency (rf) transformers operate within the higher frequencies; rf generators have many industrial uses. One of the first inventions to make use of the newly discovered electromagnetic waves was the radio. Other modern developments include induction heating and induction brazing.