MAGNETIC MATERIALS AND MAGNETIC CIRCUITS, Types of Magnetic Materials

Introduction

Energy cannot be created or destroyed, according to the law of Conservation of energy, but it can be changed from one form to another. Electrical energy cannot be stored and neither does it occur naturally. In order to satisfy the high demand, efforts are made to Generate it Continuously. However, the law of Conservation of energy states that in order to Generate Electrical energy, Some other form of energy must be Converted into an Electrical form. Using a Rotating device to convert Mechanical energy into Electrical energy is a common way to Generate electricity. A Generator is a device that Transforms Mechanical energy into Electrical energy.

Steam turbines, steam engines, or Hydraulic Turbines powered by water’s potential energy can provide the input Mechanical energy. A prime mover is a device that supplies Mechanical energy to a Generator. Some losses occur. When energy is transformed from Mechanical to Electrical form. By carefully Designing the machine,. The losses are kept to a minimum. Large Generator efficiencies are practically above 90%.

Magnetic Circuits

The magnetic lines of force in a magnetic circuit travel from the north poles through the entire circuit and back to the starting point. Iron, soft steel, and other materials with high permeability typically make up a magnetic circuit. These materials provide very little resistance to the flow of magnetic flux. Think about a coil with N turns on an iron core.

Ampere’s law

In electricity, magnetism plays a crucial role. So The electromagnetic principle underlies many electrical devices, including transformers, motors, measuring instruments, and generators. It also underpins key parts of radio, television, and aeroplanes.

1. Classification Of Magnetic Materials

Magnetic materials are classified based on the property called permeability as

1.          Dia Magnetic Material

2.           Para Magnetic Material

3.           Ferro Magnetic Material

1. Dia Magnetic Material

Dia magnetic materials are those whose permeability is less than unity. The magnet repels them.

Ex. Lead, gold, copper, glass, mercury

2. Para Magnetic Material

Materials with permeability greater than one are referred to as paramagnetic materials. A magnet will only attract these materials with a weak magnetic field.

Ex.: Copper Sulphate, Oxygen, Platinum, Aluminum.

3. Ferro Magnetic Material

The materials with permeability thousands of times more than that of paramagnetic materials are called Ferro magnetic materials. They are very much attracted by the magnet.

Ex. Iron, Cobalt, Nickel.

Permanent Magnet

Permanent magnet means, the magnetic materials which will retain the magnetic property at a] l times permanently. This type of magnets is manufactured by aluminum, nickel, iron, cobalt steel (ALNICO).

So To make a permanent magnet a coil is wound over a magnetic material. And DC supply is passed through the coil.

Electromagnet

A soft iron piece is placed inside a bobbin of insulated wire that has been wound with many turns and layers, And this device is known as an electromagnet.

This is used in all electrical machines, transformers, electric bells. It is also used in a machine used by doctors to pull out iron filing from eyes, etc.

2. Magnetic Effect By Electric Current

A magnetic field is created around a conductor when current flows through it. The magnetic field’s strength increases in direct proportion to the current. The right hand rule or Max Well’s corkscrew rule can be used to determine the magnetic field’s direction. So Electrical Flux The total number of lines on the cross-section of the magnetic core that are at a right angle to the flux direction make up the magnetic flux in a magnetic circuit.

H=N/l  AT/m

B = mH

B=m0mrNI / l   Wb/m2

ϕ =F/S

S=l/m0mra

 Φ – total flux

N – number of turns

I – current in amperes

S – reluctance

µ – permeability of free space

µ0 – relative permeability

a – magnetic path cross-sectional area in m2

l – lengh of magnetic path in metres