An inductor stores energy in its magnetic field. Interrupt the current suddenly and that energy produces a high voltage spike – how ignition coils make sparks, and why relays need flyback diodes.
How to use the Inductor Energy Calculator
- Inductance L
- Current I
- Every result field is editable: type into Stored energy and Current I plus every other field update to match.
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the inductance and current, or type an energy into the result to find the current.
Inputs explained
| Field | What to enter |
|---|---|
| Inductance L | Units: mH, µH, nH, H |
| Current I | Units: A, mA, µA, kA |
What each result means
- Stored energy = 0.5×[Inductance L]×[Current I]^2
- Flux linkage = [Inductance L]×[Current I]
Example values
How the main result changes when Current I changes and everything else stays at the example values above:
| Current I (A) | Stored energy (mJ) |
|---|---|
| 1 | 5 |
| 1.5 | 11.25 |
| 2 | 20 |
| 2.5 | 31.25 |
| 3 | 45 |
| 4 | 80 |
Formula
E = ½·L·I²
Worked example
Inputs — Inductance L: 10 mH; Current I: 2 A.
Results — Stored energy = 20 mJ; Flux linkage = 0.02 Wb.
Key terms
- Henry
- Unit of inductance, V·s/A.
Frequently asked questions
Where is the energy stored?
In the magnetic field, mostly in the core gap.
Why do relays need diodes?
Collapsing coil current would create a damaging voltage spike.
How does energy scale with current?
With its square.
What limits the energy?
Core saturation and wire heating.