Power can be expressed by the product of current and voltage. To see this, consider the units of current and voltage:
[tex][I]= \frac{C}{s} \\ \\ {[V]=\frac{J}{C}} \\ \\ {[V*I]=\frac{C}{s}\frac{J}{C}=\frac{J}{s}=W}[/tex]
Where C is coulombs (charge), s is seconds, J is joules (energy), and W is Watts, or power. See that watts are Joules per second, or the time rate of change of energy.
