# How do watts, watt-hours, etc. relate to voltage, current, and resistance?

I've worked with 12v and 5v a fair amount, and I've got a good understanding of Ohms law, series and parallel circuits, etc. But, I get a little sketchy when it comes to wattage ratings, KWHs, etc. and their relation to (now) my electric bill, (but hopefully soon to my off-grid, alternate power sources/power banks) and what I can handle as far as power consumption, etc. Any theory, links, book suggestions, practical examples, etc. will be GREATLY appreciated. Thanks so much in advance, everyone!

8 years ago
The Ampere (Amp A) is a measure of the rate at which current is flowing (charge per unit time).
The Volt (V) is a measure of the energy potential across a circuit / device.
The Watt (W) is the rate of energy conversion, which you get by multiplying V by A. (A KW is 1000 Watts)
For a total energy quantity you multiply the rate in Watts by time in seconds, to get a value in Joules (J). The Kilowatt hour is a more practical term for domestic use, but 1KWh = 1000 x 3600 J i.e 3600 KJ or 3.6 MJ.
Note that for AC current the voltage is measured as a root mean square average, because with alternating (+ve to -ve) current the mean average voltage is zero.
sykotik (author)  lemonie8 years ago
Ok, this is awesome! My EE and Physics classes are starting to come back in waves (I guess it's like a language, in that if you don't use it, you lose it). Which is precisely why I want to start using it again! :-) Thanks for the great info, and the fantastic jumping-off points for further reading!
8 years ago
Oh good. Best wishes with your project(s) L
NachoMahma8 years ago
. L gave a great answer. To do more research, try starting with a search for "Ohm's Law".