Capacitance and inductance
Inductor energy
- where
- energy stored (J)
- inductance (H)
- current (A)
Explain this equation
Works out the energy stored in an inductor’s magnetic field. Relevant to coils, contactors and why breaking inductive current causes arcing.
E is the stored energy in joules. L is the inductance in henries and I is the current flowing through it.
Energy builds up as the current rises from zero against the coil’s opposition to change. Averaging over that rise gives the ½, and the result goes with current squared.
Sense check: 0.1 H at 2 A stores 0.2 J. Double the current and the energy goes up four times.
Watch out: when current is interrupted this energy has to go somewhere, often as a voltage spike or arc. Pick the right unit: mH and H differ by a thousand.
An inductor stores energy in its magnetic field. Square its current, multiply by inductance and divide by two.
Interrupting current can create a large induced voltage. Suppression and safe switching need component-specific design.
Enter your values to see the result.
Common mistake
Using mH directly as H.
Limits
Linear inductor; saturation and losses excluded.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.