3.16 Electrical Power—Managing Motion
         for Useful Purposes

Atoms—the building blocks of all materials—are made of electrons 
spinning around a central core. Electrical installations in buildings safely manage the flow of these electrons for power and lighting

Forces That Help and Hurt the Motion of Electrons

Current is the flow of electrons—but this flow must be forced

Current, the flow of electrons (measured in amps), helps do the work. (62,510 trillion electrons flowing per second is 1 amp—a fact you do not need to remember.) 'The flow of electrons is necessary to do the work, yet it alone does not determine the work that is done.

Voltage—potential difference between two points forces the flow of electrons

If a conductor—such as a wire—connects two points with different electrical charges, pressure will cause flow from the greater to the lesser charge. 'The size of the pressure difference is called the potential differ­ence and is measured in volts. 'This potential difference alone, however, does no work and produces no power.

Voltage and current together do work

Work (power) measured in watts is the potential (volts) times the current (amps). So a very high voltage and a low current will do the same work as a very low voltage and high current. 'This makes installation using higher voltages more economical and efficient. Fewer electrons flowing permit smaller wire size and produce less resistance and heat in the wire. 'This idea is discussed many times below for electrical services, conductor size, and motor efficiencies.

Voltage drop always occurs—and must be managed by conductor size and length

Voltage must remain quite precise for acceptable electrical device operation—within 1% for lighting, 2% for general use, and 3% for motors. Variation beyond these ranges will cause rapid deterioration of light­ing ballasts and lamps, and inefficient running or damage to motors. (Motors can tolerate about +/- 10%