1. Inductance opposes changes in current

When current through a coil changes, the magnetic field around it changes too. This induces a voltage that opposes the change in current, according to Lenz's law.

2. The SI unit of inductance is the henry

Inductance is measured in henries (H), named after American scientist Joseph Henry, a pioneer in the study of electromagnetism and electromagnetic induction.

3. Coils can store energy in magnetic fields

An inductor stores energy in its magnetic field while current flows through it. The stored energy depends on both its inductance and the current passing through it.

4. Adding an iron core can increase inductance

A suitable magnetic core can concentrate magnetic flux and increase a coil's inductance compared with an otherwise similar air-core coil. The result depends on the core material and its magnetic properties.

5. More turns usually mean greater inductance

For a simple coil with unchanged geometry and core material, inductance is approximately proportional to the square of the number of wire turns. Doubling the turns can therefore produce roughly four times the inductance.

6. Inductors are essential in power supplies

Switching regulators use inductors to transfer and smooth energy, helping convert one DC voltage level into another efficiently.

7. Inductance helps tune radio frequencies

Inductors work with capacitors to create resonant circuits. These circuits can select or emphasize particular frequencies in radio receivers, transmitters, and other electronic equipment.

8. Inductance makes wireless charging possible

Wireless charging systems use magnetic coupling between coils to transfer energy without a direct electrical connection. Changing current in the transmitting coil induces a voltage in the receiving coil.

9. Transformers depend on mutual inductance

A changing current in one coil creates a changing magnetic field that induces voltage in another coil. This principle allows transformers to increase or decrease AC voltage.

10. Inductance affects electric motors

Motor windings have inductance, which influences current changes, starting behavior, and AC impedance. It is an important consideration in motor design and control.

11. Switching off a coil can create high voltage

When current through an inductor is interrupted quickly, the collapsing magnetic field can produce a large voltage. This is why relay and motor circuits often use flyback diodes or other protective components.

12. The shape of a coil matters

Coil length, cross-sectional area, number of turns, and core material all influence inductance. This is why a compact toroidal coil can behave differently from a long solenoid with the same number of turns.

13. Inductors behave differently at different frequencies

For an ideal inductor, inductive reactance increases with frequency. This makes inductors useful in filters that control which alternating-current signals pass through a circuit.

14. Inductors come in very different sizes

Some inductors are tiny surface-mounted components inside phones and computers. Others are massive coils used in industrial equipment and high-power electrical systems.

15. Inductance is closely related to electromagnetism

Inductance connects electric current, magnetic flux, and induced voltage. It is a fundamental concept in electromagnetic theory and underpins many modern electrical technologies.