Ohm's Law
Definition
The fundamental electrical law stating that voltage equals current times resistance: V = I × R. Governs all DC circuit calculations.
Why is Ohm's Law Important?
Ohm's Law is a core physics concept that describes the fundamental behavior of matter and energy. Understanding this principle enables engineers, students, and scientists to design better systems, solve real-world problems, and predict physical phenomena with precision.
Our physics calculators make it easy to compute values related to this concept, bridging the gap between theoretical understanding and practical application in engineering, education, and research.
What is Ohm's Law?
Ohm's Law states the fundamental relationship between voltage, current, and resistance in an electrical circuit: V = I × R. It is the most important equation in electrical engineering and the foundation of all circuit analysis.
The Three Forms
| Find | Formula | Example |
|---|---|---|
| Voltage (V) | V = I × R | 2A through 10Ω → 20V |
| Current (I) | I = V / R | 120V across 60Ω → 2A |
| Resistance (R) | R = V / I | 12V with 0.5A → 24Ω |
Power Formulas (Derived from Ohm's Law)
| Formula | Known Values |
|---|---|
| P = V × I | Voltage and Current |
| P = I² × R | Current and Resistance |
| P = V² / R | Voltage and Resistance |
Household Circuit Example
A US household circuit: 120V, 15A breaker
- Maximum power: P = 120V × 15A = 1,800W
- A 100W light bulb: draws I = 100/120 = 0.83A with resistance R = 120/0.83 = 144Ω
- A 1,500W heater: draws I = 1,500/120 = 12.5A (83% of breaker capacity)
- Circuit limit: Don't exceed 80% of breaker rating = 1,440W for continuous loads