Estimate voltage drop across a cable run.
Voltage drop for a single-phase circuit is approximated as Vd = (2 × I × L × ρ) ÷ A, where ρ is copper's resistivity (≈0.0175 Ω·mm²/m), L is the one-way cable length in metres, and A is the cable's cross-sectional area in mm². Many wiring regulations recommend keeping voltage drop under about 4% of the supply voltage.