Calculate energy stored in an inductor: E = ½LI².Inductance and current must both be non-negative. Negative values are not physically valid.
An inductor stores energy in its magnetic field when an electric current flows through it. This energy is proportional to the inductance and the square of the current.
When the current stops, the magnetic field collapses, and the stored energy is released back into the circuit, often causing a voltage spike.
Given:
Step 1: Apply Energy Formula
Result: A 10 H inductor carrying 5 amperes stores 125 joules of energy in its magnetic field. If the current is suddenly stopped, this energy must be dissipated safely to prevent voltage spikes.
Why does energy depend on the square of the current?
Inductors store energy in their magnetic field, which is proportional to current squared (E ∝ I²). Doubling the current quadruples the stored energy, creating dangerous voltage spikes if current is interrupted suddenly.
What's the relationship between stored energy and power?
Energy is power integrated over time (E = ∫P dt). While power represents the rate of energy transfer, stored energy in an inductor is the total potential energy in its magnetic field that will be released.
Why do inductors cause voltage spikes when switched off?
When a current-carrying inductor is suddenly opened, all stored energy must be released instantly. By E = L(dI/dt), a finite inductance and huge dI/dt create massive voltage spikes (V = L × dI/dt).
How do I safely discharge an inductor?
Use a diode (flyback diode) in parallel with the inductor for DC circuits, or use snubber circuits with resistors and capacitors for AC circuits. These provide a path for stored energy to dissipate safely.
What's the difference between storing energy in inductors vs capacitors?
Inductors store energy in magnetic fields (E = 0.5LI²) and resist current changes. Capacitors store energy in electric fields (E = 0.5CV²) and resist voltage changes. Inductors release energy through current, capacitors through voltage.
Can stored inductor energy be recovered?
Yes, in switching power supplies, the energy stored during the ON state is transferred to the output during the OFF state. Synchronous rectification and resonant circuits efficiently recover this energy.
How does frequency affect energy storage?
Frequency itself doesn't directly change the stored energy formula, but higher frequencies allow inductors to reach peak current faster (±di/dt), which increases peak stored energy for the same average current.
What inductor size needed to store 1000 joules at 10A?
Rearranging E = 0.5LI²: L = 2E/I² = 2(1000)/(10)² = 20 H. A 20 henry inductor at 10 amps stores exactly 1000 joules.
Related Tools
Decode resistor bands.
Calculate series resistance.
Calculate power dissipation.
Calculate thermal noise.
Calculate LED resistors.
Calculate capacitor values.