Electromagnetic induction occurs when an electrical wire passes through a changing magnetic field. Generators use electromagnetic induction to convert mechanical energy into electrical energy. In an AC, or alternating current, generator, the electrical current periodically reverses direction. With a DC, or direct current, generator, the current flows only in one direction. There are several other primary differences between AC and DC generators. With DC generators, the coil through which the current flows rotates in a fixed field. The two ends of the coil attach to a commutator: different halves of a single, rotating split ring. Metal brushes connect these split rings to an external circuit. The commutator balances the charges leaving and returning to the generator, resulting in a current that does not change direction. DC generators power very large electric motors — such as those needed for subway systems. Moreover, DC generators provide a reliable and efficient energy supply that can charge banks of batteries used for mobile and off-grid uses. Writer Bio
