Recall that the rate at which energy is converted from one form to another is power.

 

power = energy converted / time
power = (voltage x charge) / time
power = voltage x (charge / time)
power = voltage x current

The unit of power is the watt (or kilowatt = 1000 watts).

 

So in terms of units,

electric power (watts) = current (amperes) x voltage (volts)

Thus, 1 watt = 1 joule / 1 second = 1 ampere x 1 volt.

 

What is the power when a voltage of 120 V drives a 2-A current through a device?  What is the current when a 60-W lamp is connected to 120 V?  How much current does a 100-W lamp draw when connected to 120 V?  If part of an electric circuit dissipates energy at 6 W when it draws a current of 3 A, what voltage is impressed across it?

The 100 watt bulb draws more current and must therefore have a thicker filament.