Ohm's Law Explorer

Ohm's Law Triangle

The triangle on the stage shows how U, I and R relate. Cover the letter you want to find — the remaining two give you the formula.

U = I × R

I = U ÷ R

R = U ÷ I

Power Wheel

The wheel on the stage shows all 12 formulas connecting U, I, R and P. Each quadrant contains three ways to calculate that quantity from the other three.

P = U × I = U² / R = I² × R

Use any two values to find the third, then compute power.

What is Ohm's Law?

Ohm's Law describes the relationship between voltage (U), current (I) and resistance (R).

The voltage across a conductor is directly proportional to the current flowing through it, with the constant of proportionality being the resistance.

U = I × R

Use the triangle to remember: cover the letter you want to find, and the remaining two show the formula.

Key Quantities

I = U ÷ R = 1.00 A

P = U × I = 12.0 W

P = U² / R = 12.0 W

P = I² × R = 12.0 W

Power (P) is the energy dissipated per second. It can be calculated from any two of the three quantities using the formulas in the Power Wheel.

The Circuit

The diagram shows a DC voltage source connected to a single resistor. The blue dots represent conventional current flowing from the + terminal, through the resistor, and back to the − terminal.

U — supply voltage (slider)
R — resistance (slider)
I — resulting current = U / R
P — power dissipated = U × I

What to Watch For

As R decreases, I increases — particles flow faster.
As U increases, both I and P increase.
At very low R the current becomes very large (short circuit).
Power scales with U² ÷ R — doubling voltage quadruples power.
The wheel shows all 12 rearrangements of Ohm's Law and the power formulas.