The Inertia of Electricity
Inductance ($L$) is the property of an electrical conductor by which a change in current flowing through it induces an electromotive force (EMF) that opposes the change. In simpler terms, an inductor resists changes in current.
If capacitance is like a spring that stores energy in an electric field, inductance is like a flywheel that stores energy in a magnetic field. The unit of inductance is the Henry (H), named after American scientist Joseph Henry.
How Inductors Work
When current increases in a coil, the magnetic field expands. According to Faraday's Law, this expanding field induces a "back EMF" that tries to push the current back down. Conversely, if current drops, the field collapses and "kicks" the current to keep it flowing. This makes inductors perfect for:
- Filtering: Blocking high-frequency noise while letting DC pass.
- Power Supplies: Regulating voltage in switching power converters.
- Ignition Systems: Creating high-voltage sparks in car engines.
The Formula
Example Calculation
A coil with $50$ turns has a magnetic flux of $0.01 , \text{Webers}$ when $2 , \text{Amps}$ of current is flowing through it.
- Multiply Flux by Turns: $0.01 \times 50 = 0.5$.
- Divide by Current: $0.5 / 2 = 0.25 , \text{H}$.
The inductance is $250 , \text{mH}$.