Electric Power

Summary

• Electric Power
  • The power transfered by an electric current is the product of its…
    • voltage (the "strength" of the moving charges)
    • current (the "amount" of moving charge)

    P = VI

  • This equation is often combined with Ohm's law to produce variations.

    P = VI = I2R =	V2
    	R

• Electric Energy
  • The electric energy delivered by an electric current is the product of its power and time over which it flows — and therefore the product of…
    • voltage
    • current
    • time

    E = Pt = VIt

  • This equation can also be combined with Ohm's law to produce variations.

    E = VIt = I2Rt =	V2t
    	R

• Units
  • The watt is a joule per second (from its definition)…

    	P =	W
    		t
    ⎡ ⎢ ⎣	W =	J	⎤ ⎥ ⎦
    		s

  • and also a volt amp (from the equation above).

    	P =	VI
    ⎡ ⎢ ⎣	W =	VA	⎤ ⎥ ⎦