WIRE LAB // Volts, Amps & Gauge

Ohm's law, voltage drop, and ampacity — for a real wire run

Voltage 100 V

Current 12 A

Wire gauge #12 AWG

Run length (one-way) 25 ft

Power: P = V × I = W
Wire resistance (round trip): R = ρ × 2L = Ω
Voltage drop: Vdrop = I × R = V (% of supply)

Same math, on a physical calculator

C4× — voltage × current gives you power (P = V × I)

C4× — the wire's resistance-per-foot × the round-trip length gives total resistance

C4× — current × resistance gives you the actual voltage drop

D4÷ — voltage drop divided by the supply voltage

E5% — read that division as a percentage — over ~3% and it's time to upsize the wire

Gauge comparison — same voltage, amps & length across every wire size

AWG	Ω / 1000ft	Ampacity	Load %	V drop	% drop	Verdict

Ampacity values are conservative reference figures for low-voltage/chassis-style copper wiring (aluminum derated ~78%, ~1.64× the resistance). Real installs must follow NEC Table 310.16 (or local code) and account for insulation rating, bundling, and ambient temperature — this tool is for building intuition, not for sizing an actual circuit.

Session Log Entry — what this Wrap Up wrote to the Ledger

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