Invisible wrote:
>
> As the resistence of a circuit increases, the current flowing through it
> decreases. But that doesn't affect the actual potential across the circuit.

That's as long as the resistance on the feeding wires is small enough to
be uncompareable to the resistance of the actual device. Actually, even
then the change of the potential is just so small that you can't measure it.

> Or rather, that's what the books I've read claim, anyway...

I bet they are "for teh n00bz" -level books :).

> Yeah. That's because there's a limit to how much current the battery can
> supply.

And that's because of the internal resistance. If there were no such
thing, what would limit the current?

> Indeed, I'm told the only reason cars use lead acid batteries (which are
> very heavy yet don't actually hold that much charge) is so that they can
> briefly deliver the astronomical current required to turn the starter
> motor. 

Actually cars use lead acid batteries because they still are just the
best way to deliver that current reliably. NiCD -batteries can't stand
uneven charging, NiMH -batteries can't deliver enough current IIRC,
Litium batteries (both LiPo and Li-ion) can't stand water-freezing
temperatures. It all actually makes sense :).

> From the sources I've read, if it weren't for that, you'd only
> need a battery a fraction of the size to run the spark plugs, headlights
> and other electrical bits.

Actually you wouldn't need a battery to run those things, you'd just
need a battery/capacitor to regulate the current coming from the alternator.

-Aero

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