Electric Power


James Joule (1818–1889) England, verified Ohm's Law and determined that the heat delivered by a conductor is directly proportional to its resistance and to the square of the current through it. On the Caloric Effect of Magneto-Electricity, and on the Mechanical Value of Heat. 1843.

electric power from the definition

P =  W  = 
W   ⎞⎛
 = VI
t q t

power in terms of current

P = VI = (IR)I = I2R

power in terms of voltage

P = VI = V 
 = V2R


P = VI = I2R = V2

consumer affairs

A portion of a residential consumer electric bill. Utility companies sell electric energy by the kilowatt hour; a unit that simplifies calculating operating costs for electrical devices. The energy consumed during this particular billing cycle was quite small (when compared to similar consumers), but the rate charged by this utility was approximately double the US average in the year 2000.

Conventional (copper-based) cables are capable of transmitting power (40 to 600 MW) at high voltages (40 to 345 kV)

Line loss

Ploss = I2loadRline = 
Pload 2

and loss fraction.

loss fraction =  Ploss  =  PloadRline
Pload V2line