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may have a core of a material that increases the strength of the magnetic field. A change in the electric current flowing through an inductor creates a magnetic field that acts to inhibit that change in current. The field is proportional to the rate of change of the current, which means that fast-changing signals are inhibited more than slow-changing currents. In other words, the inductor acts as a filter, blocking higher-frequency signals. Inductors used in this way are often called chokes. Inductors are essential for many different circuit applications. Through their versatility you’ll find inductors in everything from IoT sensors to electric vehicle drive chains. They are typically low-cost components, but ship in huge numbers – the worldwide market for inductors is projected to grow from $5.1 billion in 2022, to $7 billion by 2027 .
A
HOW DOES AN INDUCTOR WORK? When the changing electric current in an inductor produces a magnetic field, this stores energy in the field. The strength of the magnetic field flux, and hence the amount of energy stored, depends on multiple factors, including the size and shape of the inductor, the number of turns of wire in the coil, and whether it has a solid core. A ferromagnetic material such as iron can greatly increase the field strength.
The ratio between the magnetic flux linkage, ΦB, and the current, I, is defined as the inductance, L, of a particular component, as follows:
n inductor is a passive component that stores energy in a magnetic field. It typically consists of a coil of wire connected to two terminals. The wire is insulated to avoid short circuits, and the coil
Figure 1: Bourns 04770x common--mode choke. (Source: Mouser Electronics)
Where, N = number of turns in the coil,
ΦB = magnetic flux and I is the current flowing through the coil.
As the magnetic field varies with time, it induces an electromotive force (EMF), or voltage, in the wire coil. Lenz’s law says that the direction of this voltage will act to inhibit the change of current. Faraday’s law of induction tells us that the
magnitude of the voltage induced, ε, is proportional to the rate of change of the magnetic field:
FUNDAMENTALS
Rearranging this equation and substituting L from our first equation, we find that:
And we can calculate the voltage as follows:
This means that if we know the inductance of a component, we can calculate the relationship
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OF INDUCTORS An inductor is one of the basic building blocks of an electronic circuit, but it can be overlooked or misunderstood by design engineers. In this article, Mouser Electronics’ Mark Patrick explains the essential basic theory behind how inductors work, their applications, and the different types of construction.
May 2024 Instrumentation Monthly
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