What is [Electromagnetism] And How Does It Work | 3 Types Of Magnetic Material
Table of Contents
ElectroMagnetism
ElectroMagnetism has attained a place of pride in electrical engineering. Without the aid of magnetism it is impossible to operate such devices as electric generators,electric motors,transformers,electric instruments.
Without the use of magnetism we should be deprived of such valuable assets as the radio, television, telephone, telegraph and ignition system of our cars, aeroplane, trucks. The purpose of this chapter is to present the salient features of magnetism so that a reader may be able to understand the function of ElectroMagnetism in electic equipments
Magnetic Material
1.Ferro magnetic materials
2.Para Magnetic Materials
3.Dia Magnetic Materials
1.Ferro Magnetic Material
The materials possessing higher degree of magnetic properties are called Ferro Magnetic Materials these materials are strongly attracted by the magnets
Example= Iron, Nickel, Cobalt,Alloy
2.Para Magnetic Materials
Materials having slight Magnetic properties are called para Magnetic Materials. They are attached by the magnet slightly
Example=Platinum,manganese, aluminium,tin, copper sulphate,ferric chloride
3.Dia Magnetic Materials
Materials having Magnetic properties which are less than ferro and para Magnetic Materials are called diamagnetic materials. Dia Magnetic Materials are repelled by the magnet
Example=Antimony,Bismuth,Glass, Mercury, Gold, Copper, Sodium chloride, Lead etc
What is ElectroMagnet
The material used for electro magnet is soft iron or soft steel with a few percentage of silicon. A coil of insulated wire is wound on a soft iron
They exhibit strong magnetism so long as there is a flow of current through the coil when there is no current through the coil the core loss it’s magnetism. These type of magnets are called electromagnet
Uses of ElectroMagnet
Electro magnets are used in Electric Generators, Motors,relays,Electric bells
What is Permanent Magnet
The magnet which retains the magnatic properties for a long period is known as permanent magnet. Aluminium, Nickel,Iron,Cobalt is the most important hard materials used for making permanent magnet. The permanent magnets available in different shapes
Bar magnet

U‑Shaped Magnet

Permanent magnets are made by instruction process. This is done by winding a coil over the piece of steel to be magnetised and passing a large D.C current through the coil. When the current flows through the coil the steel piece is magnetised. If the current is stopped a major portion of the magnetism is retained and it becomes permanent magnet. The magnetism retained by the steel after the removing of magnetising force is called the residual magnetism
Uses of Permanent Magnet
Permanent magnets are used in electrical measuring Instruments,magnetic Chuck’s, speakers and cycle dynamos
What is Magnetic Field
The region around a permanent magnet or the space around a current carrying conductor occupied by the lines of force is called the magnatic field of force or magnatic field
What is Magnetic Flux
The amount of magnatic lines of force in a magnatic field known as Magnetic Flux
These Flux lines from a closed path and the path followed by the flux lines is known as Magnetic circuit. The unit of magnetic flux is Weber and is represented by the letter Φ
What is Magnetic Flux Density
The flux density is the magnatic flux per unit area taken perpendicular to the direction of the magnatic flux
It is usually denoted by the letter, B and its unit in Tesla . If a flux of Φ Weber is passing through an area of ‘A’ square matre,then the flux density B is given by B=Φ/A web/square meter
What is Permeability
The flow of flux produced by the Magnet not only depends on the magnatic field strength but also depends an one important property. It is related to the medium in which magnet is placed
The permeability is defined as the ability in which the magnatic material forces the magnatic flux through a given medium
There are two types of permeabilitys
1.Absolute permeability
2.Relative permeability
Absolute permeability
The magnatic field strength decides the flux density to be produced by the Magnet around it in a given medium
The ratio of magnatic flux density in a particular medium to the magnatic field strength producing that magnatic flux density is called absolute permeability of that medium. It is denoted by µ
µ = B/H
Relative Permeability
The relative permeability is defined as the ratio of flux density produced in a medium to the flux density produced in free strength and under identical conditions
If the magnatic field strength H producing a flux density B in the medium while flux density Bo in free space then the relative permeability is
µr=B/BO
What is MMF (MAGNETO MOTIVE FORCE)
The force which establishes the magnatic flux in a magnatic circuit is called Magneto motive force. It corresponds to electro motive force in an electric circuit.
The Magneto motive force is produced when a current passes through a coil of wire. The mmf is the product of the number of turns of the coil and the current through the coil.
The unit of mmf is Ampere turns and it is represented by a letter F. If a current of I ampere is flowing through a coil of N turns the m.m.f. produced is equal to
F= NI ampere turns
Ampere turns is the unit of magneto motive force The ampere turns of a magnatic circuit are given by the product of the turns of the coil and the amperes in the coil
Ampere turns = NI
What is Reluctance
Reluctance is the property of a material which opposes the establishment of magnatic flux in it. It is the resistance offered to the passage of magnatic flux through a material
Reluctance = mmf/Φ
Reluctance unit is AT/WB
What is Magnetic Field Strength
The Magneto motive force per unit length of the magnatic circuit is termed as Magnetic field intensity. The magnatic field intensity is denoted by the letter H and it’s unit is Ampere turns/meter. It is also known as magnetising force or magnatic field strength
H = NI/ℓ
H = magnetising force
I = current through the coil,in Amperes
ℓ=length of the magnatic circuit in meters
What is Permeance
It is the reciprocal of reluctance. It corresponds to in electric circuits. Its unit is web/AT
Permeance = 1/Reluctance web/AT
What is Reluctivity
It is specific reluctance and corresponds to resistivity in electic circuit.