Inductor Energy Calculator
Find the energy stored in a magnetic field of an inductor.
Calculate
Formulas
E = ½ × L × I²L = inductance (H), I = current (A), E = energy (J)
Inductor Energy
Inductors store energy in magnetic fields, unlike capacitors which use electric fields. Energy is proportional to inductance and the square of current. Used in power converters, filters, and energy storage.
Energy Stored in an Inductor
An inductor stores energy in the magnetic field created by current flowing through its coil. The stored energy depends on inductance and the square of the current:
E = ½ × L × I²E is energy in joules, L is inductance in henries, I is current in amps.
Like a capacitor's dependence on voltage, inductor energy scales with the square of current. Doubling the current quadruples the stored energy.
Worked Example
L = 100 µH carrying 3 A:
E = 0.5 × 0.0001 × 3² = 0.00045 J = 0.45 mJ
Why Inductors Resist Current Change
Because energy is tied to current, an inductor opposes sudden changes in current — interrupting the current forces the stored energy to go somewhere, often as a high-voltage spike. This is the principle behind boost converters and ignition coils, and the reason flyback diodes are placed across relay coils to absorb that energy safely.
Frequently Asked Questions
What happens if I suddenly open an inductor circuit?
The collapsing magnetic field induces a large voltage spike (V = L·dI/dt) that can damage switches or semiconductors. Protection diodes or snubbers absorb it.
How does this compare to a capacitor?
A capacitor stores energy in an electric field and resists voltage change; an inductor stores energy in a magnetic field and resists current change. They are duals of each other.
Where is inductor energy storage used?
Switching power supplies, transformers, motors, and energy-recovery systems all rely on the inductor's ability to store and release magnetic energy.