Physics Finals Inductance and Magnetism

inductor

a passive electrical

component formed by a wire wound

around core and which exhibits the

property of inductance.

inductor

When a length of wire is formed into

a coil it becomes an

inductance

It is the property of an electrical

circuit that opposes the change in

current, expressed in henry

Inductance

property of an

electric circuit by which an

electromotive force is induced in it

as the result of changing magnetic

flux.

Electromagnet

temporary magnet

production due to flow of electric

current.

Electromagnetic induction

production

process electric form magnet.

Air core, Ferromagnetic, Ferrite, Powdered Iron Core, Ceramic core, Laminated Core

Types of inductors based on core

core

The material &

design of the _____ specifies the

inductance, current capacity &

operating frequency of the inductor.

Air Core Inductor

hollow, which gives them

low permeability and low inductance. They are

most effective in high-frequency settings.

Ferromagnetic/Iron Core Inductor

consists of a core

that is made up of a ferromagnetic

material.

Ferromagnetic/Iron Core Inductor

the iron core of this inductor

has unique magnetic characteristics

which strengthen the magnetic

field.

Ferrite Core Inductor

Transformers

High-frequency applications

Ferrite

is a material with high

magnetic permeability made from the

mixture of iron oxide (ferric oxide,

Fe2O3) & a small percentage of other

metals such as nickel, zinc, barium…

Hard Ferrites and Soft Ferrites

There are two types of ferrites

Powdered Iron Core

Inductor

These inductors are

composed of magnetic

iron material with air

gaps.

Powdered Iron Core

Inductor

This

construction allows

the core to store more

energy than other

types of inductors.

They also offer low

eddy current and

hysteresis losses.

Ceramic Core Inductor

are dielectric

and cannot store much energy,

but they do provide low

distortion and heat loss.

Laminated Core Inductor

consist of thin steel sheets

stacked to form the core.

These stacks help block eddy

currents and minimize energy

loss

Toroidal Core Inductor, Drum/Bobbin Core Inductor

Inductor Based On Core Design

Toroidal Core Inductor

These inductors are made of a

donut-shaped iron core wrapped in

wire. For the closed-loop, circular

shape, toroidal inductors create

strong magnetic fields.

Drum/Bobbin Core Inductor

It is a cylinder with two flat

discs at each end.

Drum/Bobbin Core Inductor

does

not provide a closed magnetic

path instead the flux goes

through the disc into the air

gap & then enters the core

through the second disc at the

other end. It provides a large

air gap for its magnetic field

to store more energy…

Multi-Layer Inductor

have multiple

layers of wire wounded on top

of each other

have large inductance due to an

increase in the number of turns

of the winding.

Thin Film Inductor

type of inductor is

designed on a substrate of

thin ferrite or magnetic

material. A conductive

spiral shaped trace of

copper is placed on top of

the substrate. The design

allows stability &

resistant to vibrations.

Molded Inductor

The core is made from ferrite or

phenolic material.

Coupled Inductor

These inductors feature two wires wound

around a common core. The changing

magnetic flux due to first winding induces

emf in the second winding; this phenomenon

is known as mutual inductance.

Power Inductor

These inductors are specifically designed

to withstand high current without reaching

the magnetic saturation region. To

increase the saturation current rating,

the magnetic field of the inductor is

increased, which causes EMI

(Electromagnetic interference). To reduce

the EMI, most power inductors are used

with proper shielding. They are available

from few amps to a few hundred amps in

both SMD & through-hole packaging.

Radio-Frequency RF Inductor

designed for

high-frequency

application

high impedance and core

losses at high frequency

Chokes

simple inductor but it is specifically designed for blocking

(choking) high-frequency signals.

AF chokes, RF chokes

two types of chokes

Audio frequency choke

is used for blocking Audio

frequency and only allowing DC current.

Radio-frequency choke

are designed to block RF

frequency while allowing DC & audio frequency.

Variable Inductors

these inductors are designed to have variable inductance.

Variable Inductors

The most common design of _____ is having a movable ferrite core.

Moving the core along the winding will increase or decrease the permeability

which affects the inductance of the inductance. The core can be designed to

slide or screwed in or out of the coil.

variometer

It provides a

continuous change in inductance.

variometer

is made up of two coils

(one inside the other) connected in series having 1:1 ratio. The mutual

induction between these two coils plays the entire role in varying the

total inductance. The inner coil can be rotated using a shaft which

changes the direction of the magnetic field lines created by that coil

number of turns, cross-sectional area, prescence of a magnetic core, the way the turns are arranged

Factors which affect the inductance of an inductor

Coefficient Coupling

representation of interaction of

two inductors

0 to 1

Coefficient Coupling have a value from

not coupled

k=0

loosely coupled

k<0.05

tightly coupled

k>0.5

perfectly coupled

k=1

self inductance

When the e.m.f. is induced in the circuit while the current changes

mutual inductance

When the e.m.f. is induced in a circuit

by a change of flux due to current

changing in an adjacent circuit, the

property is called

Mutual Inductance

the value of inductance with coefficient coupling. it can either decrease or increase the net inductance of pair of series-connected compares with the condition of zeromutual inductance

Mutual Inductance

M=k√L1+L2

in phase

For two ac eaves that are ____ The inductance is increased compared with the

condition of zero mutual inductance.

out-of-phase

For two waves that are ____ the net inductance is decreased relative to the

condition of zero mutual inductance.

RL Time constant

fixed time interval required for the current to make a change from one value to another

Magnetism

natural phenomenon in which some material can

be attracted by a magnet but not other

materials.

Electromagnetism

Magnetism produced by an electric current rather

than by a natural magnet,

Hans Christian Oersted

discovered electromagnetism

Magnet

substance that attracts pieces of iron,

steel, nickel, cobalt.

Magnetic Field

The region surrounding a magnet represented

by magnetic flux lines, like electric

flux lines.

NATURAL MAGNET

permanent magnets.

ARTIFICIAL MAGNET

created by

electromagnetism, can be either temporary

or permanent magnet.

Retentivity, Residual Magnetism, Coercive Force

Magnetic Properties

Magnetic Field Intensity

magnetomotive force per unit length of path of the magnetic flux

Magnetic Field Intensity

also called as the magnetizing force or the magnetic potential gradient

Permeability

the ability of a material conduct magnetic flux through it

Reluctance

property of a material that opposes flux flow, counterpart of resistance