Radio Wave The basic physical laws that make radio possible are known as Maxwell’s equations, identified by James Clerk Maxwell in 1864. Maxwell’s equations show that a changing magnetic field will produce an electric field, and a changing electric field will produce a magnetic field. When alternating current (AC) moves through a wire or other physical conductor, some of that energy escapes into the surrounding space as an alternating magnetic field. That magnetic field creates an alternating electric field in space, which in turn creates another magnetic field and so forth until the original current is interrupted. This form of energy in transition between electricity and magnetic energy is called electromagnetic radiation, or radio waves. Radio is defined as the radiation of electromagnetic energy through space. A device that produces radio waves is called a transmitter, and a complementary device that detects radio waves in the air and converts them to some other form of energy is called a receiver. Both transmitters and receivers use specially shaped devices called antennas to focus the radio signal in a particular direction, or pattern, and to increase the amount of effective radiation (from a transmitter) or sensitivity (in a receiver).