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Result
Ohm's Law Formulas Reference
| To Find | Formula 1 | Formula 2 | Formula 3 |
|---|---|---|---|
| Voltage (V) | V = I × R | V = P ÷ I | V = √(P × R) |
| Current (I/A) | I = V ÷ R | I = P ÷ V | I = √(P ÷ R) |
| Resistance (Ω) | R = V ÷ I | R = V² ÷ P | R = P ÷ I² |
| Power (W) | P = V × I | P = I² × R | P = V² ÷ R |
⚠️ Single-Phase Only: This calculator is for DC and single-phase AC resistive loads. For three-phase systems, multiply watts by √3 (1.732) × power factor: I = P / (V × 1.732 × PF). For AC motors and inductive loads, actual current is higher than calculated — divide by the power factor (typically 0.7-0.9 for motors).
Ohm's Law Explained for Contractors
Ohm's Law is the foundation of electrical work. It describes the relationship between voltage (V), current (A/amps), resistance (ohms), and power (watts). If you know any two values, you can find the other two.
V = I × R | P = V × I | P = I² × R
For everyday electrical work: voltage is the "pressure" pushing electricity, current (amps) is how much electricity flows, resistance (ohms) opposes the flow, and power (watts) is the work being done. Understanding these relationships lets you troubleshoot circuits, size components correctly, and work safely.