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. 

Perhaps the first electric motors were simple electrostatic devices created by the Scottish monk Andrew Gordon in the 1740s. The theoretical principle behind production of mechanical force by the interactions of an electric current and a magnetic field, Ampère's force law, was discovered later by André-Marie Ampère in 1820. The conversion of electrical energy into mechanical energy by electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury, on which a permanent magnet (PM) was placed. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire. This motor is often demonstrated in physics experiments, brine substituting for toxic mercury. Though Barlow's wheel was an early refinement to this Faraday demonstration, these and similar homopolar motors were to remain unsuited to practical application until late in the century.
When were the first electric motors developed?
By who?
What was his job?
Where was he from?
Where they complex?
What were they?
What kind is in a watch?
Are the ones in a watch big?
How high can the rating go on big one?
How many different types of sources provide the power?
What does DC stand for?
What about AC?
Who discovered Ampere's force law?
When?
Did Micheal Faraday show something?
when?
What did he change Electrical energy into?
Did he do this with a magnet?
What did he put the wire into?
What has since replaced that?
1740s
1740s
Andrew Gordon
Andrew Gordon
monk
monk
Scotland.
Scottish
no
 simple electrostatic device
simple electrostatic devices
 simple electrostatic devices 
unknown
unknown
yes
The largest of electric motors are used for ship propulsion
100 megawatts
100 megawatts
electric power source type, internal construction
electric power source type, internal construction
direct current
 direct current 
alternating current
alternating current
André-Marie Ampère
André-Marie Ampère
1820
1820
yes
demonstrated by the British scientist Michael Faraday in 1821
1821
1821
mechanical energy
mechanical energy
yes
electromagnetic means 
pool of mercury
pool of mercury
permanent magne
permanent magne