How do you wire amp gauge?

A #10 copper wire with an insulation rated at 90 degree C has a rating of 30 amps.

I would recommend #8 AWG for any residential wiring application for 40A.

Either #6AWG copper of #4 AWG aluminum wire rated for 90 c. These values are rated at exactly 75 amps so you still need to calculate for voltage drop, conduit fill, and ambient temperature. So as a...

30 amps.

In my experience there is no such thing as 32 gauge wire. If it existed it would be so small as to be breakable by 2 fingers, probably the size of a human hair or smaller. I'm using 32 gauge wire in...