Ohm's Law Triangle and Calculator
How to Use
Click any coloured section of the triangle to choose which quantity to solve for — that section goes dark with a ?.
| Section clicked | Solves for | Formula used |
|---|---|---|
| Top (amber) — V | Voltage | \(V = I \times R\) |
| Bottom-left (blue) — I | Current | \(I = V / R\) |
| Bottom-right (green) — R | Resistance | \(R = V / I\) |
Drag the two sliders at the bottom to set the known values. The result and power (P) update immediately in the calculator panel on the right.
Ohm's Law
\[V = I \times R\]
| Symbol | Quantity | SI Unit |
|---|---|---|
| V | Voltage (potential difference) | Volt (V) |
| I | Current | Ampere (A) |
| R | Resistance | Ohm (Ω) |
Rearranged:
\[I = \frac{V}{R} \qquad R = \frac{V}{I}\]
Power
Power is always shown as a bonus calculation:
\[P = V \cdot I = I^2 R = \frac{V^2}{R}\]
| Unit | Equivalents |
|---|---|
| 1 W = 1 V·A | 1 mW = 0.001 W |
The Triangle Mnemonic
Cover the quantity you want to find — the remaining two show what to do:
- Cover V → multiply the other two: \(I \times R\)
- Cover I → divide top by bottom-right: \(V / R\)
- Cover R → divide top by bottom-left: \(V / I\)