Ohm's Law Wheel
Four quantities, each with three ways to reach it. Hover or tap any formula and it explains itself on the right.
Pick a formula
Each colored quarter belongs to one quantity, and its three outer cells are the three ways to calculate it. Move over any of them for the plain-language version.
Where the twelve come from
There are only two laws here: V = I × R and P = V × I. Substituting one into the other, then solving for each quantity in turn, produces exactly twelve arrangements. The wheel saves you doing that algebra at the bench with a hot iron in one hand.
The three that matter most
If you memorize nothing else: V = I × R sizes resistors, P = V × I tells you what runs hot, and P = I² × R explains why slightly thinner wire gets dramatically warmer. Everything else on the wheel is convenience.
Prefer to type numbers? The Ohm's law calculator solves all four at once on a live circuit.