Unit 1 1

UNIT - 1 1.
0 Magnetic circuits
• 1.1 Introduction to magnet - Magnetic field

Introduction to magnet - The material which attract the
magnetic material like iron, nickel, cobalt etc. is called magnet.
This property of magnet is called Magnetism.
Properties of Magnet.
• Opposite poles of magnet attract and same pole repeal each other.
• Maximum force at poles and zero at middle of magnet.
• If we put magnetic material near the magnet it work as magnet
• If we break magnet into some part then each part will work as
separate magnet
• Electromagnets- Electromagnets consist of a coil of wire wrapped

around a metal core made from iron.
. When this material is exposed to an electric current, a magnetic field

is generated, making the material behave like a magnet.
• The strength of the magnetic field can be controlled by controlling

the electric current.
• electric fan, electric doorbell, induction cooker, magnetic locks, etc.

• Temporary magnets -Temporary magnets can be magnetised in the

presence of a magnetic field.
• When the magnetic field is removed, these materials lose their
magnetic property. Iron nails and paper clips are examples of the
temporary magnet. Example- Paperclips, iron nails
• Permanent magnets - Permanent magnets are those magnets that

are commonly used. They are known as permanent magnets because
they do not lose their magnetic property once they are magnetised.
• Example- Magnets used in refrigerators, speakers, fridge and
magnetic compass
How can a magnet lose its magnetism
• By heating
• Knocking
• time ( Age )
• Stronger magnetic field.
1.1.2 MAGNETIC FIELD
• The magnetic field is a region around a magnetic material or a

moving electric charge within which the force of magnetism
acts.
• The magnetic field is the area around a magnet, where there
is magnetic force.
1.2.2 TYPES OF MAGNETIC MATERIALS
(1) FERRO MAGNETIC MATERIAL - A type of material that is

highly attracted to magnets and can become permanently
magnetized is called as ferromagnetic.
Ex: Iron, Steel, Cobalt, Nickel
Applications: Ferromagnetic materials are used in magnetic

recording devices, such as for cassette tapes, floppy discs for
computers, .
1.2.2 TYPES OF MAGNETIC MATERIALS
2. PARA MAGNETIC MATERIAL - It is a substance or body which

very weakly attracted by the poles of a magnet, but not
retaining any permanent magnetism.
They attract the lines of forces weakly. Ex: Aluminum,
Platinum
3. DIA MAGNETIC MATERIAL - Diamagnetic materials are those

materials that people find non-magnetic such as wood, water,
gold, copper, etc. These materials show the property of
diamagnetism. They are not attracted to any magnetic field.
1.3.1 MAGNETIC FLUX (Φ)
The number of Magnetic Field lines flowing through a closed surface is
known as Magnetic Flux. It calculates the total magnetic field that travels
across a specific surface area.
The SI unit of magnetic flux is Weber (Wb).

1.3.2 MAGNETIC FLUX DENSITY (B)
Magnetic flux density, commonly denoted as B, is a vector quantity that
represents the strength and direction of a magnetic field at a particular
point in space.
It is a measure of the number of magnetic field lines passing through a

unit area perpendicular to the field lines. Magnetic flux density is closely
related to the concept of magnetic field, and the terms are often used
interchangeably.
The equation for calculating the force on a wire is Force (N) = magnetic
flux density (T) × current (A) × length (m) or, in short F = B I L.
1.3.2 MAGNETIC FLUX DENSITY (B)
1.3.3 MAGNETIC FIELD STRENGTH (H)
• The total number of magnetic field lines penetrating an area is called
the magnetic flux. The unit of the magnetic flux is H = At/m, ampere-
turns per meter.
1.4 MAGNETO MOTIVE FORCE - MMF
The Magneto motive force (MMF) is defined as the work done in
moving a unit magnetic pole once around the magnetic circuit.
It is a magnetic pressure that tends to set up magnetic flux in a magnetic

circuit. Mathematically, the mmf is the product of current and number
of turns of a coil.
Consider the coil consisting of N turns and an electric current of I

1.4 MAGNETO MOTIVE FORCE - MMF
Unit of MMF
Since MMF is a product of current in amperes (A) and
number of turns (T) in a coil, thus
Unit of MMF = Ampere − Turns (or AT)
1.5.2 PERMEABILITY (μ)
• Magnetic permeability is defined as the magnetic flux density B
produced within a material by a magnetising field divided by the
magnetising field’s magnetic field intensity H.
• Hence, magnetic permeability (Greek mu) is defined as B/H.
• The magnetic permeability formula is given as follows;

• Magnetic permeability (μ) = B/H
• Where B = magnetic intensity and H = magnetising field.

Unit 1 1

Uploaded by

Copyright:

Available Formats

Unit 1 1

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Unit 1 1

Uploaded by

Copyright:

Available Formats

UNIT - 1 1.

• 1.1 Introduction to magnet - Magnetic field

• Maximum force at poles and zero at middle of magnet.

• If we put magnetic material near the magnet it work as magnet

• Electromagnets- Electromagnets consist of a coil of wire wrapped

. When this material is exposed to an electric current, a magnetic field

• The strength of the magnetic field can be controlled by controlling

• electric fan, electric doorbell, induction cooker, magnetic locks, etc.

• Temporary magnets -Temporary magnets can be magnetised in the

• Permanent magnets - Permanent magnets are those magnets that

• The magnetic field is a region around a magnetic material or a

(1) FERRO MAGNETIC MATERIAL - A type of material that is

Applications: Ferromagnetic materials are used in magnetic

2. PARA MAGNETIC MATERIAL - It is a substance or body which

3. DIA MAGNETIC MATERIAL - Diamagnetic materials are those

The SI unit of magnetic flux is Weber (Wb).

It is a measure of the number of magnetic field lines passing through a

It is a magnetic pressure that tends to set up magnetic flux in a magnetic

Consider the coil consisting of N turns and an electric current of I

• The magnetic permeability formula is given as follows;

You might also like