Practical takeaway
An inductor stores energy in a magnetic field. Coils are used in filters, tuned circuits, chokes, matching networks and many RF stages.
Electricity & Electronics
Inductors
See how current through a coil creates a magnetic field and why the coil resists rapid changes in current.
TECHNICIAN FOUNDATION9 of 16
Technician exam focus
Know that inductance is measured in henrys and that current through a conductor creates a magnetic field.
A coil stores energy in a magnetic field
Current creates a magnetic field.
Current through a conductor produces a magnetic field. Winding the conductor into a coil concentrates that field.
An inductor opposes a change in current.
When current tries to rise or fall, the changing magnetic field induces a voltage that opposes that change. Steady DC is different from changing current.
With AC, frequency matters.
Inductive reactance is XL = 2πfL. Raise the frequency or the inductance and XL increases, so an inductor opposes AC current more strongly.
Why hams care
Inductors appear in chokes, filters, tuned circuits, matching networks, RF amplifiers, and power-supply circuits.
STEMulation
See both jobs of an inductor
Current0.00 A
Magnetic fieldcollapsed
With the switch open, current is zero and the magnetic field has collapsed.
The moving wave is slowed down for teaching; the calculations use the selected frequency.
Inductive reactance XL
Series-circuit current