P = E/t
- P power in W
- E energy in J
- t time in s
E = P t
Example
Calculate the electric energy dissipated in a bulb of 50 W during 24 h.
E = P t
E = (50) (24 * 3600) = 4.32 x 106 J
Remark : time in s(seconds) and the energy in J(Joule)
The unit of time can also be : h(our). Then the unity of energy is Wh (Watthour)
E = P t
E = (50)( 24) = 1200 Wh = 1.2 kWh