Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use. The largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, and so on. COUNT 5
QSN1 What is the largest rating of an electric motor? ANS1 100 megawatts QSN2 What is the main example of a DC power source? ANS2 batteries QSN3 What does AC stand for? ANS3 alternating current QSN4 What does DC stand for? ANS4 direct current QSN5 In what device are small motors commonly found? ANS5 electric watches