Originally Posted by Bottomfeeder
Hmmm, this just kind of bothers me a bit. Voltage is definitely analogous to the pressure, no debate there, but amperage is analogous to the flow (in gallons per minute, say) not the "speed". The speed would be analogous to the current density. Consider this, the Mississippi has a much higher current than a firehose, yet the water speed is higher coming out of the nozzle. If we were looking at just the speed it'd appear that a firehose has more current than a slow moving river. And that just ain't so.
Wattage is not analogous to the flow the water. It's more analogous to how much work the water can do. I can cut any metal with a high pressure stream of water, even though the gpm of the water is very low. There isn't a clean analogy to Wattage unfortunately. It's really flow*pressure.
Voltage => Pressure
Amperage => Flow
Flow /= Speed
Watts => Pressure * Flow (whatever that means)
Another 2 cents for the pile.
Not to put too fine a point on it, but... The current
of the Mississippi is much lower than the firehose, but the "watts" (gallons per minute) delivered is still high. Why? because with such a huge (mile wide in many places) pipe, the resistance
is incredibly low. Think of the Mississippi as a kind of "superconducting" water pipe. Aw, hell. This doesn't work, either.
I can't claim the water analogy is perfect by any means. It's a handy way to describe electrical terms to non-electrical types. You can kind of
create other analogies for things like capacitance and resistance using the water model, but when you look closely, the analogy breaks down. Consider inductance, for example.
Wouldn't it be cool if you could make water flow in a pipe simply by placing it next to another pipe with water flowing in it? (Ok, with water flowing back and forth
in the pipe. You get the idea.)
Anyway, it's an interesting discussion. One of my former employers once talked of a college course he took while getting his BSEE. For a good portion of the class, the instructor strenuously avoided electrical terms, and taught the concepts using analogies from the physical world. My friend said it was a tough course, and really made everyone think, but it was interesting. I think I'd better stick to electricity, since I can understand it (in as much as I do
understand it) just as it is.