On 10/20/2011 5:46 AM, John Martindale wrote: > Well actually Jeff, the current in the circuit stays the same. Refer > John. You are incorrect in this situation. Adding the resistance of the rheostat (as we increase the dimming effect) increases total circuit impedance. ALTHOUGH this is accompanied by a SLIGHT decrease in resistance of the lamps (due to the lamps having a positive temperature coefficient of resistance) this effect is STILL not enough to be considered of any consequence in this application. THUS, since the dimmer's resistance ADDS to the resistance of the lamps (which for all practical purposes has not changed) TOTAL circuit resistance INCREASES. Since the applied voltage remained the same (12V) and Total Resistance INCREASED, Total circuit current decreased as a result, and power decreased. The converse is true as we increase brightness.
-- Glenn Martin
