Ohm’s law reference
What is Ohm’s law?
For an ideal resistive circuit, voltage V equals current I multiplied by resistance R: V = I × R.
Power relationships
P = V × I, P = I² × R and P = V² / R. Units are volts, amperes, ohms and watts.
Worked example
A 12 V source across a 6 Ω ideal resistor produces 2 A. The resistor dissipates 24 W.
Important limitations
These relationships are directly applicable to resistive DC circuits. AC circuits containing reactance need impedance and phase-angle analysis. Zero-value and special-case circuits may not have a unique solution.