Stuart, you've proved me right!! [and calculator is Calif govt, not US]
I pointed out you CANNOT change the voltage of the battery, it is what it is
the rheostat DOES NOT 'drop the voltage', it consumes current by increasing resistance - power is a direct function of current flow - no current no power, regardless of how many volts - in the formulas it's
resistance that's changed w/ the switch
when you turn the switch to it's minimum the voltage is the same, and
the current drained from the battery is the same, but it gets used by the hot switch and doesn't reach the motor - the motor takes 6.3amps to turn full speed, less will slow it down
plug those figures in but DO NOT change the 6v, change the resistance, which is
what the switch does, adds resistance - you'll see that for 6v adding resistance lowers the amperage, where it's lowered is at the motor - still the same in the circuit [and from the battery], but some is being 'burned off' in the extra resistance
"
Current is a function of voltage, not the other way around. In the little diagram of the batteries and wire, the lamp grew dimmer because there was less current supplied to it..BECAUSE the resistance wire reduced the available voltage."
NO
current is a function of
resistance, and the increased resistance of the switch "stops" some of the current flow - the available voltage is the same - 6V, and the battery is still losing the same amount of amps
your error is thinkin that voltage is the variable in the circuit, that voltage does the work, that current is only a function of voltage - as I said before, the current is the movement that produces the work - there is still the same voltage 'push' happening, but some of the
same level of current is being lost as heat along the way so it doesn't reach the motor
Brendan puts it in a different equation, same thing: x= the amps that the total resistance draws [motor+switch], y=current that gets to the motor, z=current lost at the switch as heat
think of a battery as a repository of amps [why they rate them that way] not volts - different things on the truck use different amounts of amps - when the amps are all gone the battery is dead, but it's still 6volts, just needs to be refilled!
better?
Bill
