Ohm's law
V = I × R
I = V / R
P = V × I = I²R = V²/REducational reference
Electrical formulas
A compact reference for the stable equations used by PowerTotals calculators.
Single-phase power
S = V × I
P = V × I × PFThree-phase power
S = √3 × VLL × I
P = √3 × VLL × I × PFConductor resistance
R = ρ × L / A
Vdrop = I × Rpath
Ploss = I² × RpathPower triangle
PF = P / S
Q = √(S² - P²)
φ = cos⁻¹(PF)Battery energy
Wh = V × Ah
runtime = usable Wh / load WIdeal transformer
Vp / Vs = Np / Ns = Is / IpResistor networks
Series: Req = ΣR
Parallel: 1/Req = Σ(1/R)Symbols
| Symbol | Meaning | Common unit |
|---|---|---|
| V | Voltage | volt (V) |
| I | Current | ampere (A) |
| R | Resistance | ohm (Ω) |
| P | Real power | watt (W) |
| S | Apparent power | volt-ampere (VA) |
| Q | Reactive power | volt-ampere reactive (VAR) |
| PF | Power factor | ratio, 0–1 |