Inductor

Inductor is the most difficult component to understand, compared to resistor and capacitor.

I would like to try making this component easier to understand.

Edited by Lim Siong Boon, last dated 20-Dec-2012.

Topic Discussion Overview

Inductor Introduction

Inductor Introduction

Typical symbol of the inductance.

Inductor is simply a piece of wire coil. A striaght wire do not have inductance. A slight bend in the wire will starts to introduce inductance on the wire. I have been working on electronics for quite some time, but have not understand the practical aspect of inductance on a circuit.

An inductor makes no impact on a DC (direct current) Voltage or Current. Like a capacitor, it affects the AC (alternative current) components. Inductor allows DC or lower frequency components to flow through it while it block AC or higher frequency components. For this reason, inductor is often used in line with a wire carrying power supply, to block any noise on the supply line.

The inductance of a inductor is affected by the following parameters,
– the area size of the coil
– the number of turns to make up the coil
– the diameter size of the wire or the length of the coil

Formula for inductance, L = (r x o x N x N x A) / L

where,
r – normalised permeability (/o)
o – magnetic constant (4π 10−7 H/m)

No. of Turns	Loop , D	Wire , d	Core (r)	Inductance	Increase in inductance when
1	10mm	1mm	Air (1.0)	15nH	reference
2	10mm	1mm	Air (1.0)	59.9nH	increase in turns no.
1	20mm	1mm	Air (1.0)	38.3nH	increase , D
1	10mm	2mm	Air (1.0)	10.6nH	reduce , d
1	10mm	1mm	Ferrite, manganese zinc (640.0)	9.6uH	increase material permeability

Normalised Permeability (r),
of Air is about 1.0
of Ferrite is about 640

Reference:
Coil Inductance Calculator, http://www.eeweb.com/toolbox/coil-inductance
Air Cored Inductor Calculator, http://www.m0ukd.com/Calculators/air_core_inductor_calculator/

The reference table above computes the inductance of a wire coil for each change in the parameters. An increase in the number of turns increases the magnetic field through the coil, hence increases in inductance value by quite a lot. An increase in the coil (D) increases the coil circumference, hence more surface area contributing to the field within the coil resulting in an increase of the inductance. Inserting a high permeability material into the coil provides a lower resistance for the magnetic field which helps to increase the inductance.

??????
The increase in the wire (d) while all parameters remains, reduces the resistance, however reduces the inductances. This also means that if the wire is a perfect conductor (0Ω or no resistance), there will be no inductance. Inductance needs resistance to exists. This is something that I need to understand.
??????

Inductor impedance formula

XL = 2π x f x L

XL -> Inductance Reactance
π -> 3.14159
f -> frequency
L -> Inductance

Capacitive reactance Xc = 1 / (2 π f C)
Resonant frequency f0 = 1 / (2 π √(L C))

Brands Available

Keyword: Inductor, Inductance