Ohm's Law
Ohm's law in all its rearranged forms, the power equations that come with it, worked examples, and the cases where the law does not actually hold.
Questions people ask
Does Ohm's law work on AC?
Yes, with impedance Z in place of resistance: V = I × Z. For a purely resistive load the two are the same. Once capacitance or inductance is involved you also have to track phase.
What is the Ohm's law triangle?
A memory aid: V on top, I and R below. Cover the quantity you want and the remaining layout shows the formula — cover V and you are left with I × R.
Who was Ohm?
Georg Ohm, a German physicist who published the relationship in 1827. It was dismissed at the time and only recognised years later; the unit of resistance now carries his name.
Does this page work offline?
Yes, after the first visit. The service worker caches it, so the reference stays available with no connection.
Last updated 22 August 2026