Wire Gauge (AWG)
The thickness of a wire, measured in American Wire Gauge. Smaller numbers mean thicker wire and more current capacity: 14 AWG carries 15 amps, 12 AWG carries 20, 6 AWG carries 55.
Gauge is the safety contract at the center of every circuit: the breaker rating must never exceed what the wire can carry. The everyday residential ladder runs 14 AWG (15A lighting and outlet circuits), 12 AWG (20A kitchen, bath, garage), 10 AWG (30A dryer, water heater), 8 – 6 AWG (40 – 60A range, EV charger, AC), and 4 AWG and up for feeders and service conductors.
Two practical realities follow. Long runs need a size bump to manage voltage drop, so the garage subpanel might use 4 AWG where the table says 6. And the classic dangerous shortcut, putting a 20-amp breaker on 14-gauge wire to stop trips, turns the wire itself into the fuse.
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- Conduit : Protective tubing (metal or PVC) that individual wires are pulled through, used where cable would be exposed to damage, weather or burial: garages, outdoors, underground runs.
- Junction Box : An enclosed box where wires are spliced together.
- Knob and Tube Wiring : The original residential wiring method (roughly 1880 – 1940s): individual conductors on ceramic knobs and tubes, with no ground wire and air-cooled design that modern insulation defeats.
- Aluminum Branch Wiring : Branch-circuit wiring installed in millions of homes from about 1965 – 1973 that develops loose, overheating connections at outlets and switches.