This calculator applies the exact inductor identity EL=½LI² to the selected inductance and current. It compares stored magnetic energy with a disclosed 0.3 mJ reference. It does not predict energy delivered across a spark gap or ignition.
Sparking Dynamo · Selected Magnetic-Energy Ledger
Explore selected inductor stored-energy arithmetic without treating it as delivered spark energy or an ignition guarantee.
Equation Used
- Inductance and current are the selected instantaneous values.
- The inductor is represented by the lumped identity E=½LI².
- The 0.3 mJ value is a comparison reference only.
- Rotation in the drawing is illustrative and is not coupled to the calculation.
- Switching losses, resistance, parasitics, spark-gap dynamics, mixture conditions and safety are excluded.
The 0.3 mJ value is retained only as a disclosed comparison reference, not a universal ignition threshold.
Selected stored-energy reference
The diagram identifies an illustrative rotating magnet and coil, while the energy bar carries the exact selected stored magnetic energy. Rotation is illustrative and does not enter the energy identity.
What the calculator determines
Select inductance and current. The calculator reports stored magnetic energy, its ratio to 0.3 mJ, the current that would store 0.3 mJ at the selected inductance, and the signed difference from that reference.
Selected magnetic-energy identity
EL=½LI²; ratio=EL/0.3 mJ; Iref=√(2×0.3 mJ/L); difference=EL−0.3 mJ.
Selected-input example
At L=2 mH and I=3 A, stored magnetic energy is 9 mJ, or 30 times the disclosed 0.3 mJ reference. The current for 0.3 mJ stored energy at 2 mH is about 0.548 A.
Stored energy, not delivered spark energy
Switching losses, winding resistance, parasitic capacitance, arc voltage, gap geometry and discharge duration determine how much stored energy reaches a spark. Ignition also depends on mixture, pressure, temperature, flow and electrodes, so 0.3 mJ is not a universal ignition threshold.
Questions
Is stored magnetic energy the spark energy?
No. Actual delivered spark energy can be lower and requires a transient circuit and gap model or measurement.
Does exceeding 0.3 mJ guarantee ignition?
No. The value is retained only as a comparison reference; minimum ignition energy is condition-specific.
References & Further Reading
- Wikipedia contributors. Dynamo. Wikipedia
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
