Inductor
Related wiki pages: Electronic Theory, Capacitors, Resistors, Impedance
An inductor is a device that stores energy in a magnetic field. Inductors are short circuits to DC current, but their impedance rises as AC current passing through them has its frequency increased. Extremely high frequency currents see inductors as open circuits.
In some ways, inductors behave as the opposite of capacitors. This property is critically important to the circuit design of oscillators.
Fundamentally, inductors consist of a conductor, which is usually wrapped into a coil. Many inductors have an insulator inside the coil that has magnetic properties that raise the inductance. Such materials include powdered iron toroids and ferrite toroids.
Inductance
Inductance (L), measured in henries (H) is the effect which results from the magnetic field around a currentcarrying conductor. Current flowing 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.
Inductive Reactance
The impedance of an inductor is given by the formula
 <math>Z = j \omega L \,</math>
where <math>Z\,</math> is the impedance, <math>\omega\,</math> is <math>2 \pi f\,</math>, and <math>f\,</math> is the frequency. <math>j\,</math> is "operator j" from phasor analysis.
In practical terms this leads to:
<math> X_c = 2 \pi F L </math> where:
 <math> X_c </math> is capacitive reactance
 F is the frequency of operation in Hertz
 L is the inductance in Henries
Inductor formulae
Construction  Formula  Dimensions 

Cylindrical coil  <math>L=\frac{\mu_0\mu_rN^2A}{l}</math> 

Straight wire conductor  <math>L = l\left(\ln\frac{4l}{d}1\right) \cdot 200 \times 10^{9}</math> 

<math>L = 5.08 \cdot l\left(\ln\frac{4l}{d}1\right)</math> 
 
Short aircore cylindrical coil  <math>L=\frac{r^2N^2}{9r+10l}</math> 

Multilayer aircore coil  <math>L = \frac{0.8r^2N^2}{6r+9l+10d}</math> 

Flat spiral aircore coil  <math>L=\frac{r^2N^2}{(2r+2.8d) \times 10^5}</math> 

<math>L=\frac{r^2N^2}{8r+11d}</math> 
 
Toroidal core (circular crosssection)  <math>L=\mu_0\mu_r\frac{N^2r^2}{D}</math> 

Online calculators
Various inductance calculators
Electronic Theory  
Physical quantities  Current * Gain * Impedance * Power * Q of a circuit * Radiated Power Measurement * Reactance* Resistivity * Resonance * Voltage 
Components  Baluns * BipolarJunction Transistors * Capacitors * Diodes * Inductors* Lasers * Microphones * Resistors * Transformers * Wire 
Circuits  Attenuators * Digital Signal Processing (DSP) * Dummy load * Filters * LC filters * Power Supply Design * Rectifier Circuits 
Design  Amplifier Design * Oscillator Design 
Electromagnetic Waves  Relative power (Decibels) * Harmonics * Interference and BPL 