What is an inductor? Definition of an inductor? Introduction to inductor characteristic parameters and categories

Inductors are one of the three major passive components, alongside resistors and capacitors, serving as fundamental and widely used components in electronic circuits. A passive component, the inductor is an electromagnetic induction component, typically formed by winding an insulated wire a certain number of turns around a support or core to create a coil, also known as an inductor coil or inductor. The main uses of inductors include filtering noise, suppressing transient currents, reducing electromagnetic interference (EMI), and power conversion.
Passive components refer to electronic components that cannot be simulated by an equivalent circuit as a power supply; therefore, they play a crucial supporting role in electronic circuits.

Inductance is the ratio of the magnetic flux produced by an alternating current flowing through a conductor to the current that produces this flux, both within and around the conductor.
When a direct current flows through an inductor, only fixed magnetic lines of force are present around it, unchanging over time. However, when an alternating current flows through the coil, the magnetic lines of force around it change over time. According to Faraday's law of electromagnetic induction – magnetic field generating electricity – the changing magnetic lines of force generate an induced electromotive force (EMF) at both ends of the coil, which is equivalent to a "new power source".
When a closed loop is formed, this induced EMF generates an induced current. Lenz's law states that the total magnetic lines of force generated by the induced current attempt to oppose the change in the original magnetic lines of force. Since the change in the original magnetic lines of force originates from the change in the externally applied alternating current source, from an objective perspective, the inductor coil has the characteristic of resisting changes in current in an AC circuit. The inductor coil has a characteristic similar to inertia in mechanics; in electrical terms, this is called "self-inductance." The sparks that occur when a knife switch is opened or closed are caused by the high induced EMF generated by this self-inductance phenomenon.
➤In short, when an inductor coil is connected to an AC power source, the magnetic lines of force inside the coil constantly change with the alternating current, causing the coil to continuously generate electromagnetic induction. This electromotive force generated by the change in the coil's own current is called "self-induced EMF".
Therefore, inductance is merely a parameter related to the number of turns, size, shape, and medium of the coil. It is a measure of the coil's inertia and is independent of the applied current.