An electric motor is an electric machine that converts electrical energy into mechanical energy. Electric motors operate following a connection between an electric motor's magnetic field and winding currents to generate force within the motor. Electric motors are used in the transportation industry, in both motoring and generating and braking modes to produce electrical energy from mechanical energy. Electric motors are used in industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. Electric motors can be powered from batteries, motor vehicles or rectifiers or from the power grid or generators. Large electric motors are used for ship propulsion, pipeline compression and pumped-storage applications.