What is inductor: Symbol, Applications and Types

As we begin our studies in 2022, we will work together to decode inductance today.

We can clearly deduce the function of resistance and capacitance from their names—blocking current and keeping charge, respectively—but inductance appears to be unsatisfying. In this case, the sense is induced current. The inductance can function normally because of the induced current.

Ⅰ. Who invented the inductor?

The discovery of induced current is a very remarkable achievement. Because scientists were the first to discover that electricity causes magnetism, Danish scientist Hans Christian rested observed that a little magnetic needle was deflected around the current line in an unintentional experiment. That is, a magnetic field exists surrounding the current line. Today's scientists agree that electromagnetism is the best theory. André-Marie Ampère, the famous Ampere's law, which is the law of the right-handed spiral, explained this discovery further. The magnetic field's direction is determined by the right hand.

After electricity generates magnetism, another key discovery is that magnetism generates electricity. There was a brilliant scientist named Faraday in the history of electromagnetics. Faraday's most important contribution was the discovery of electromagnetic induction, which eventually served as a firm experimental foundation for Maxwell to develop Maxwell's equations and forecast electromagnetic waves. Faraday is regarded as the inventor of electricity as well as the inventor of alternating current.

The electromagnetic induction phenomenon occurs when a portion of a closed circuit's conductor cuts the magnetic line of induction in a magnetic field, causing a current to flow through it. When a magnetic field travels through a coil, the induced current generated causes the ammeter's pointer to revolve, as seen in the diagram below.

Generators are built on the electromagnetic induction phenomenon. Bearings and end cover connect the stator and rotor of the generator, allowing the rotor to rotate in the stator and cut the magnetic lines of force, generating induced electric potential, which is drawn via the terminal and connected in the loop to generate current. As we discussed in a recent post, the discovery of this generator ushered in the second industrial revolution: the power revolution.

At the same time, in the United States, there was a renowned scientist named Joseph Henry. In reality, Henry was working on a similar project at the same time as Faraday: in 1829, he enhanced the electromagnet by replacing the iron core insulation with wires. A huge number of wires can be twisted around the iron core, considerably increasing the magnet's power and resulting in an electromagnet capable of supporting 2,063 pounds, a world record at the time. Henry was working on a super electromagnet in 1931, as Faraday was proposing the law of electromagnetic induction. He learned of Faraday's experiment's success while still deciding on an appropriate experimental location. Henry, on the other hand, did not abandon his research into the link between electricity and magnetism. Henry found the self-induction phenomenon in this experiment: when the current in a conductor changes, the magnetic field around it changes, and the magnetic flux changes as well. As a result, the conductor generates induced electromotive force. This electromotive force always prevents the original current in the conductor from changing. The self-induced electromotive force is this electromotive force. The theoretical basis of inductance is self-induction: current changes are blocked.

We call the unit of inductance Henry (H) in honor of Henry's significant discovery: The inductance of the circuit is 1 Henry, which results in an electromotive force of 1 volt if the rate of change of current in the circuit is 1 ampere per second.

Ⅱ. How to use the inductor?

Self-inductance and mutual inductance are the two most prevalent inductor applications.

The utilization of the above-mentioned self-induction phenomena is known as self-inductance. Self-inductance is a circuit property (usually a coil). The voltage in the circuit will fluctuate as the current changes due to the magnetic effect induced by the current. Self-inductance is an inductance that applies to a single circuit, or in other words, it is an inductance that occurs in a single coil. For single coils or chokes, this effect is used.

The formula for self-induction:

The number of coil turns multiplied by the change in magnetic flux per unit time equals the magnitude of the induced voltage VL.

Mutual inductance is an electromagnetic induction theory in which a change in current in one circuit causes a change in voltage across a second circuit due to the action of the magnetic field connecting the two circuits. Transformers make use of this effect.

Only alternating current can work, regardless of self-inductance or mutual inductance, and only the changing magnetic field produced by the changing current may trigger induced current. The inductance of direct current is similar to an extended wire.

Wire inductance

Inductance exists for alternating current regardless of whether the wire is a straight line or a coil. Inductors typically employ coils because the magnetic field coupling between the coil's multiple turns improves inductance and allows the wire to be enclosed in a smaller volume. Straight wire inductance may be ignored in most low-frequency applications, but when the frequency rises to the VHF range and beyond, the inductance of the wires becomes quite considerable, and the connections must be maintained short to reduce the influence.

The inductance of the wire can be calculated pretty accurately using calculations, but the inductance of the coil is significantly more complicated and depends on a variety of parameters, including the coil's shape and the constants of the materials inside and around it. In general, an understanding of Maxwell's equations can be used to calculate inductance. Mathematics, on the other hand, may not necessarily be simple. Skin effect and other aspects must be considered in addition to this high-frequency signal, as it influences surface current density and magnetic fields, which may necessitate the employment of Laplace equations. As a result, various practical simplifications can be used to make inductance calculations and equations more accessible. For example, when utilizing "thin" wires, it is common to assume that the current distribution across the wire is constant over the wire's diameter, which substantially simplifies the calculation of the wire's inductance.

You can use the following formula to calculate the inductance of a straight wire and get a rough estimate of the inductance.

Wires and coils have a lot of inductance. Inductance is an important property that can play a significant role in various circuits.

Ⅲ. Inductor circuit symbol

The coiled nature of the inductor is represented by the inductor's circuit symbol. The inductor or transformer's air core or magnetic core might be indicated in a variety of ways.

Despite the widespread use of simple inductors in many circuits, transformers are also used in a variety of applications.

Ⅳ. Types of the inductor

Wire inductance has a relatively simple structure and low cost, but has poor frequency characteristics; the second is wire-wound inductance, in which hollow wire is wound. Inductors used in actual circuits can be divided into multiple types based on different implementation methods: one is wire inductance, which has a relatively simple structure and low cost but has poor frequency characteristics. The inductor has the smallest loss, as well as the smallest parasitic capacitance. The performance of the ceramic winding inductor is similar to that of the hollow winding inductor, but its construction strength is greater; the ferrite core winding inductor is tiny in size but has a big inductance value, and the loss is frequency related; printing The cost of laminated wire-wound inductors is inexpensive, but the Q value is also poor. Spiral inductors are the third type. MMICs often use rectangular microstrip spiral inductors, although circular spiral inductors provide better high-frequency properties.

Inductors are commonly employed as radiofrequency chokes in bias circuits in the design of radiofrequency circuits. The radiofrequency reactance is high, yet the DC resistance is low, allowing radio frequency signals to pass through. Inductors can also be used to tune filters and resonators, as well as impedance matching circuits. The inductance stability, loss characteristics, reactance accuracy, and self-resonance frequency should all be considered in the real design. Consider the inductor's parasitic capacitance, Q value, and current tolerance.