this is basic electrical engineering for first year diploma electronics students

1. Magnetic
circuit
By
G R chaure

2. Content
 Introduction
 Magnet
 Types of magnet
 Important definition related to magnetism
Magnetic circuit

3. Introduction
 Relation between magnetism and electric
current first observed by Oersted

4. Magnet
 It is piece of solid substance which exhibit a
property of attracting small pieces of certain
material such as iron ,steel etc

Magnetic circuit

5. Types of magnet
 Natural magnet
the natural magnet have the properties of
naturally present
 Electromagnet
it is formed by passing an electric current
through insulated wire wound on certain
material
Magnetic circuit

6. Definition related to magnetism
Magnetic field
the magnetic field is defined as the region near
a magnet within which the effect or influence of
magnet is felt
Magnetic flux
The total number of lines of force in magnetic
field .
Denoted by Ø and measured in Webber
Magnetic circuit

7. Magnetic flux density
The flux per unit area (A) measured in plane
perpendicular to the flux
it is measured in Tesla and denoted by B
Magnetic flux density B = Ø/A
Magnetic field strength (H)
The force experienced by unit north pole placed
at that point in the magnetic field
- The unit N pole is the N pole with the pole
strength of 1 Wb
Magnetic circuit

8. The magnetic field strength is measured in Newton /
Weber Or ampere / meter or ampere turns /
meter
The relation between B & H is
B= µ H where µ is called permeability
Permeability
It is the ability of material to carry the flux line .
If the material allows the flux lines to pass through it
easily then the material is said to have a high
permeability
Ex : iron , steel ( high permeability )
Wood ( low permeability )
Magnetic circuit

9. Absolute permeability
The ratio of flux density in particular medium (
other than vacuum or air ) to the magnetic field
strength
µ = B / H henry per meter
permeability for free space or vacuum
If the medium in which the magnet is kept is air
or vacuum
Then the ratio of flux density(B) and magnetic
field strength H
µ0 = B / H
it always remain constant 4 ¶ * 10−7
Magnetic circuit

10.  Relative permeability
It is defined as the ratio of flux density in
particular medium produced by magnet to the
flux density in a air or vacuum by the same
magnet under identical operating condition
µr = B / 𝐵0
 B = flux density in medium
 𝐵0 = flux density in air or vacuum
Magnetic circuit