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

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!

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lemonieBest Answer (author)2009-03-09

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.

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sykotik (author)lemonie2009-03-09

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!

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lemonie (author)sykotik2009-03-09

Oh good. Best wishes with your project(s) L

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NachoMahma (author)2009-03-09

. L gave a great answer. To do more research, try starting with a search for "Ohm's Law".

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