Ferrite inductors use a ferrite core—a ceramic material that offers high magnetic permeability while remaining a poor electrical conductor. This unique combination makes ferrite inductors ideal for broadband filtering, power conversion, and EMI suppression.
Wrap at least 20 turns of wire around a ferrite rod. Measure the resulting inductance with your meter and note the value as L and the number of turns as N (20 in this example).
The AL value is a core‑specific constant that relates inductance to turns. Compute it with:
AL = [(100 / N)²] × L
Example: If L = 25 µH and N = 20, then
AL = (100 ÷ 20)² × 25 µH = 5² × 25 µH = 25 × 25 µH = 625 µH
Use the AL value to calculate inductance for a different number of turns:
L = AL ÷ [(100 / N)²]
As you add turns, the inductance rises because more wire concentrates the magnetic field, increasing the coil’s magnetic coupling.
