4.5: Inductors
An inductor is a passive component built to store energy within its magnetic field. It can be fabricated by coiling a wire around a magnetic core. When current is permitted to flow through this inductor, it is observed that the voltage across the inductor is directly proportional to the time rate of change of the current. Mathematically,
This relationship is expressed using the passive sign convention, where 'L' represents the constant of proportionality, also known as the inductance of the inductor.
The inductance of an inductor is influenced by factors such as its size, the materials used, and the construction method. The unit of measurement for inductance is the Henry (H). Inductance is a measure of the ability of a device to store energy in the form of a magnetic field. Also, it is a characteristic that allows an inductor to resist changes in the current flowing through it.
In addition to being referred to as inductors, these components can also be called coils or chokes. The circuit symbol for an inductor is presented in Figure 1.
Figure 2 shows a graphical representation of the relationship between voltage and current for an inductor whose inductance does not depend on the current, also known as a linear inductor.
A nonlinear inductor, on the other hand, would not have a straight-line plot, as its inductance fluctuates with the current.
Inductors, akin to capacitors, are commercially available in various values and types. In practical applications, inductors typically have inductance values ranging from a few microhenrys, as seen in communication systems, to tens of henrys, as used in power systems. Inductors can either be fixed or variable, and their core can be composed of various materials, including iron, steel, plastic, or even air.
