Inductors, also known as chokes, reactors, and dynamic reactors. It is an element that can convert electric energy into magnetic energy and store energy in the magnetic field. The structure is similar to the transformer and has the characteristics of DC and AC resistance. In electronic circuits, inductance mainly plays the role of filtering, current limiting, tuning, oscillation, interference suppression and magnetic field generation.

Inductance units and parameters mainly include the following aspects:

The symbol l indicates that the basic unit of the inductor is Henry (H), which is commonly used in milli Heng (MH) and micro Heng（ μ H) Is the unit. Conversion relationship: 1h=10^3mh=10^6 μ H。 That is, the unit conversion is generally 10 cubic. Inductance is divided into general inductance and precision inductance;

General inductance: the error value is 20%, expressed in M; The error value is 10%, expressed in K. Precision inductance: the error value is 5%, represented by J; The error value is 1%, expressed in F. For example, 100k is 10 μ H. The error is 10%.

Inductance can be made of conductive material coiled around the magnetic core, typically copper wire, or the magnetic core can be removed or replaced with ferromagnetic material. The core material with higher permeability than air can restrict the magnetic field more closely around the inductive element, thus increasing the inductance.

The chips of some inductive components can be adjusted. Thus, the inductance can be changed. The small inductor can be directly etched on the PCB board with a method of laying spiral tracks. Small value inductors can also be used to make transistors. The same process is used in integrated circuits. In these applications, aluminum interconnects are often used as conductive materials.

No matter what method is used, based on the actual constraints, the most widely used is a circuit called "spinner", which uses a capacitor and an active element to show the same characteristics as the inductive element. Inductive elements used to isolate high frequencies are often composed of a metal wire passing through a magnetic column or bead.

Inductors can also be divided into self inductors and mutual inductors.

When there is current flowing through the coil, a magnetic field will be generated around the coil. When the current in the coil changes, the magnetic field around it also changes correspondingly. The changed magnetic field can make the coil generate induced electromotive force (induced electromotive force) (electromotive force is used to represent the terminal voltage of the ideal power supply of the active element), which is called self inductor.

When two inductance coils are close to each other, the magnetic field change of one inductance coil will affect the other inductance coil, which is mutual inductance. The size of mutual inductance depends on the degree of coupling between the self inductance of the inductance coil and the two inductance coils. The element made by using this principle is called mutual inductor.