Everything about Inductors totally explained
An
inductor is a
passive electrical device employed in
electrical circuits for its property of
inductance. An inductor can take many forms.
Physics
Overview
Inductance (
L, measured in
henrys) is an effect which results from the
magnetic field that forms around a current-carrying
conductor.
Electric current through the conductor creates a
magnetic flux proportional to the current. A change in this current creates a change in magnetic flux that, in turn, generates an
electromotive force (EMF) that acts to oppose this change in current. Inductance is a measure of the amount of EMF generated for a unit change in current. For example, an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. The number of loops, the size of each loop, and the material it's wrapped around all affect the inductance. For example, the magnetic flux linking these turns can be increased by coiling the conductor around a material with a high
permeability.
Stored energy
The
energy (measured in
joules, in
SI) stored by an inductor is equal to the amount of work required to establish the current through the inductor, and therefore the magnetic field. This is given by:
»
By using a
ferromagnetic core the inductance is increased for the same amount of copper, raising the Q. Cores however also introduce losses that increase with frequency. A grade of core material is chosen for best results for the frequency band. At
VHF or higher frequencies an air core is likely to be used.
Inductors wound around a ferromagnetic core may
saturate at high currents, causing a dramatic decrease in inductance (and Q). This phenomenon can be avoided by using a (physically larger) air core inductor. A well designed air core inductor may have a Q of several hundred.
An almost ideal inductor (Q approaching infinity) can be created by immersing a coil made from a
superconducting alloy in
liquid helium or
liquid nitrogen. This supercools the wire, causing its winding resistance to disappear. Because a superconducting inductor is virtually lossless, it can store a large amount of electrical energy within the surrounding magnetic field (see
superconducting magnetic energy storage).
Formulae
The table below lists some common formulae for calculating the theoretical inductance of several inductor constructions.
Further Information
Get more info on 'Inductors'.
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