Derived value
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Ohm's Law Calculator
Solve voltage, current, resistance, and power for resistive circuit magnitudes, with formulas and consistency checks.
At a glance
- Computes
- Voltage, current, resistance, and power for a resistive circuit, with consistency checks.
- You supply
- Any two of voltage, current, resistance, and power, with units.
- Use when
- A steady DC circuit whose element behaves as a plain resistance.
- Not for
- AC circuits with reactance, or components whose resistance changes with current.
Model
Resistive circuit
| Quantity | Value | Unit | Status |
|---|
V = I R; P = V I; P = I^2 R; P = V^2 / R
How?
How this is calculated
The solver uses Ohm's law and the resistive power identities. It accepts magnitudes only and checks extra supplied values against the solved resistive model.
Formula: V = I R; P = V I; P = I^2 R; P = V^2 / R
Series and parallel resistance
Series resistances add because the same current crosses each component. Parallel conductances add because each branch sees the same voltage. Thus 100, 220, and 330 ohms give 650 ohms in series and 56.8966 ohms in parallel. A useful check is that a parallel total must be below the smallest branch, while two equal branches give exactly half one resistance.
RC time constant
A resistor and capacitor charge or discharge exponentially. The time constant is resistance times capacitance. A 10 kilohm resistor with 100 nanofarads gives 1 millisecond, and the first-order cutoff is 159.155 hertz. After one through five time constants the charge reaches 63.212, 86.466, 95.021, 98.168, and 99.326 percent of its final value.
Real capacitors include leakage and series resistance, and alternating-current networks need impedance and phase. This instrument keeps the ideal first-order model explicit. Reduce a resistor network to its equivalent resistance, then use Ohm's law mode to solve current, voltage, and power.
Sources
- OpenStax College Physics 2e, Resistance and Resistivity. OpenStax. Retrieved .
Method last reviewed