Wire Gauge Required Question

pianotuna wrote:
Hi,


I love extreme examples.

100 volts X 1 amp = 100 watts
98 volts X 1 amp = 98 watts

That looks like 2% loss of voltage = 2% loss of power to me.

only if you can hold current constant as voltage changes, that doesn't happen in a DC linear circuit.

for your example R must change from 100ohms to 98 ohms, you've changed two variables. Hold R constant and I decreases to 0.98A.

Remember a cable is a DC linear circuit. with a constant resistance, (which for all practical purposes the cable is) you can't go from 100v at 1 amp to 98 Volts and 1 amp UNLESS R (the load) ALSO CHANGES (decreases). For a constant resistance dropping from 100V to 98 volts, the current also drops from 1 A to .98A. therefore power goes from 100 watts to 98x.98= 96 watts, a 4% loss for a 2% voltage drop.

in a dc linear circuit when you hold one variable constant (in this case resistance) you can't change voltage or current independently. change one and the other MUST ALSO CHANGE.

That's what salvo and others are ignoring.