Re: Generator question - negative current

Posted by humanpotatohybrid On 2023/11/25 4:59:19

Jim those are good things to check but breakers should only trip because of overcurrent conditions; i.e. shorts. Having corrosion, bad connections, etc. will increase the resistance of the circuit and decrease the current flowing thru it by causing various voltage drops.

Example: let's say a partially corroded wire has 1/10 ohm resistance on a headlight circuit which normally has 10 amps flowing thru it, 6 volts. Roughly speaking, the resistance will cause a voltage drop of 1V. Assuming the current is similar still, it will dissipate 10 watts. Furthermore, the headlight itself will be running on 5V instead of 6V. Realistically, the increased resistance will drop the total current too, but it's hard to calculate because light bulbs have a nonlinear draw.

FYI, light bulbs do not have a linear relationship between voltage and power, or between power and brightness. Higher voltages give disproportionately less power than what would be expected from P = V^2/R since the resistance rises from heat (by a factor of about 10x from room to operating temp); however, higher powers give disproportionately more light, greatly offsetting the earlier effect. In other words, the light efficiency drops much faster than linear when operated below the intended voltage. And likewise, bulbs designed for higher wattage use are more light-efficient than weaker bulbs, even when running at the same voltage and having the same voltage rating. E.g. it takes way more than 25 four-watt night lights to equal one 100-watt incandescent.