Theoretically if you ran 20ft of 2awg for 100amp could run the appropriate size wire on the ground side for a 1-2ft run at 100 amp. In this case you'd run a 4ga for the short ground run.
What I'm unsure of...say you're powering a 15 amp light bulb direct off the battery. The light is 15ft from the battery, and it is decided to ground the light back at the battery. To determine wire size, is only a single 15ft run considered? Or is the circuit considered as needing wire big enough to run 15 amps at 30ft?
I'd reasonably assume it's only 1 run @15ft because 15 amps is travelling along the hot and being used by the light, the ground only has to support 15amps to the light? Whats the authority on this?
What I'm unsure of...say you're powering a 15 amp light bulb direct off the battery. The light is 15ft from the battery, and it is decided to ground the light back at the battery. To determine wire size, is only a single 15ft run considered? Or is the circuit considered as needing wire big enough to run 15 amps at 30ft?
I'd reasonably assume it's only 1 run @15ft because 15 amps is travelling along the hot and being used by the light, the ground only has to support 15amps to the light? Whats the authority on this?