Magneto, mag NEE toh, is an electric generator that provides spark ignition in some internal-combustion engines. Magneto ignitions are used in lawn mowers and in some aircraft and motorcycles. A magneto operates on two basic principles: (1) The movement of a conductor in a magnetic field produces an electric current in the conductor, and (2) A sudden interruption of the flow of the current in the conductor can induce (generate) large voltages.