Basic Units

Power

Finally, we can relate current and voltage together. Power (P), which has units of watts (or joules/second), is the rate of change of energy.
We know that W=QV and so:

 

because I is defined as the rate of change of charge. Power is defined is positive when it is being dissipated (when heat is being produced, for example).


Named after Charles Prescott Joule, 1818-1889 (see: www.ece.umr.edu/faculty/Chowdhury/J_P_Joule.html)
Named after Andre Marie Ampere, 1775-1836
(see: www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Ampere.html
Named after James Watt, 1736-1819 (see: http://www.history.rochester.edu/steam/carnegie/)