Ohm's Law Calculator
Enter any two known values to find the rest. The calculator uses Ohm's law (V = I × R) and the power equation (P = V × I).
- Formulas used: R = V ÷ I, P = V × I
Ohm's Law and Power Formulas
P = V × I = I² × R = V² ÷ R
Worked example
A 250 Ω resistor in a 4 to 20 mA loop carries 20 mA. V = 0.02 × 250 = 5 V and P = 0.02² × 250 = 0.1 W, so a 0.25 W resistor is more than adequate.
Frequently Asked Questions
What is Ohm's law?
Ohm’s law states that the current through a conductor is proportional to the voltage across it: V = I × R, where R is the resistance in ohms.
How do I calculate power from voltage and resistance?
Use P = V² ÷ R. For example, 24 V across 480 Ω dissipates 1.2 W.
Does Ohm's law apply to AC circuits?
For purely resistive AC loads it applies using RMS values. With inductance or capacitance, replace R with impedance Z and include the phase angle for power.
Learn more on the blog
Basics of Ohm's law
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
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