Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: Power, current, and voltage

Learn more physics!

Most recent answer: 10/31/2009
Is it possible to find out the watts of something without knowing the amps? I know the volts, its 5.0, but i don't know how to find the watts?
- Hanna (age 13)

Yes - you don't necessarily need to know the current (Amps) that runs through an electrical appliance (bulb, fridge, computer, etc.) in order to find  how much energy per time (power, Watts) the appliance is consuming. Just knowing the voltage (Volts) is not enough, though. But if you know the resistance (Ohms) of the appliance AND the voltage across it, you can use Ohms' law, voltage = resistance*current to first find the current and then you can find the power from, power=voltage*current.


(published on 10/31/2009)

Follow-up on this answer.