Bill,
I want to believe you..I want you to show me the error of my ways. I used the neat calculator you linked, compliments of Uncle Sam (?). Every time I plug in a lower voltage..lower than 6 volts, the current drops in proportion to it.
You keep saying "the power to the motor must be reduced"...it is. The rheostat drops the voltage, or power available to the motor. With this reduced voltage, current will flow less..the motor turns slower.
If you have a circuit with twelve volts, measured on a meter, and no work is being done..nothing is running, no motor or light, then when you put your amprobe on the circuit, it will read zero. You have 12 volts of PRESSURE, but nothing is flowing..no CURRENT.
If you turn the heater switch all the way to its slow fan speed setting, you reduce the voltage to it minimum, the current flow to its minimum, but the little coils get red hot..ouch!
They don't get red hot from current flow, its flowing its least. You can see this when you plug those figures into the calculator. Its flowing its least because if has the least amount of voltage pushing it. The excess voltage is given off as heat.
A 6 volt fan motor draws 6.3 amps. The windings have .95 ohms of resistance. If you plug these values into Uncle Sam's chart, the only way to change the outcome is to play with the voltage.
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.
This is the way I see it. I found a Ohmite rheostat on the shelf, powered it up with 12 volts and stuck my meter on it. As it was turned up, the voltage climbed, as it was turned down, the voltage went down.
If there had been a small motor in the circuit when I did this silly test, its speed would have fluctuated with the rotation of the knob.
The motor wasn't magically wanting more or less CURRENT, it still wanted it full operating current,BUT there wasn't adequate VOLTAGE there to push it..to supply it. Current is something that is USED, it isn't waiting in the wire to go somewhere.
If you have a wire with a million volts in it and everything is turned off, you don't have any current flow..zip, nada!
I think this needs to be put to bed. I am sticking with this theory, flawed or otherwise. Thanks for the great links, and just because I live south of the 49th, doesn't mean I embrace the current (pun) administration.
My dear old father was born on a farm outside of Edmonton in the dead of winter, so I guess I am part "north of the 49th".
Stuart
