* In electricity generation, a generator is a device that converts motive power (mechanical energy) into electrical power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines and even hand cranks. * The modern-day generator works on the principle of electromagnetic induction discovered by Michael Faraday in 1831-32. Faraday discovered that the above flow of electric charges could be induced by moving an electrical conductor, such as a wire that contains electric charges, in a 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.