Understanding Hysteresis Curves and Magnetic Materials in Electromagnetism

 
The importance of hysteresis
curves
 
The 
magnetic
properties 
of a
ferromagnetic
substance
 can be
obtained from the 
size
and 
shape
 of the
hysteresis loop.
Fig. shows the
hysteresis loops 
for 
soft
iron 
and 
steel
.
 
The 
retentivity
 of 
soft iron 
(
OC
) is greater than
that of 
steel
 (
OC'
).
 i.e., 
soft iron 
retains
 more magnetism 
than 
steel
,
when the 
magnetizing force 
is totally 
removed
.
The 
coercive force 
for 
soft iron 
(
OD
) is smaller
than that for 
steel 
(
OD’
).
 ie. 
iron
 is more 
readily demagnetised 
than 
steel.
 
 
 
the 
permeability
 
µ = (BIH) 
for 
soft iron 
is greater
than that for 
steel
.
The 
susceptibility
  
χ = (MIH) 
for 
soft iron 
is
greater than that for 
steel.
The area of the 
B-H loop 
for 
steel
 is much 
larger
than 
that for 
soft iron
.
Thus the 
energy loss 
per unit volume per cycle of
magnetisation is 
greater
 for 
steel
 than that for
soft iron
.
 
Choice of Magnetic materials
.
 
Permanent Magnets. 
Materials used for making
magnets are never taken through a cycle
.
So 
hysteresis loss 
is a 
minor
 consideration in
these cases.
These materials should have 
high retentivity 
and
high coercivity
.
So 
steel
 is a 
suitable material 
for 
permanent
magnets.
.
 
 
Recently a 
number of alloys
, having large
values of coercivity have been developed for
the purpose of construction of 
permanent
magnets.
The very suitable alloy of highest coercivity is
named as vicalloy (vanadium, iron and alloy
cobalt).
 
 
Electro-magnets
 
The material for the cores of electromagnets
should have 
maximum flux density
 with
comparatively 
small magnetising field 
and 
low
hysteresis loss.
Soft-iron
 is an ideal material for
electromagnets
.
 
Transformer cores
 
Materials for transformer cores, 
telephone
diaphragms 
and 
chokes
 etc.. (
which are meant
for obtaining high magnetic flux
) are frequently
subjected to many cycles of magnetisation in 
one
second.
 So the 
material 
selected for the purpose must
be associated with 
high magnetic induction 
and
low hysteresis loss
.
 
Soft-iron
 is 
better than 
steel
 for these
purposes.
By alloying 
soft-iron
 with 
4% silicon
,
transformer steel
” is produced.
It has a 
higher initial permeability 
and is an
ideal material for cores of transformers.
Alloys
 of 
iron
 and 
nickel
, called 
permalloys
have also very large initial permeabilities
 
Ferrites
 
Their permeability is
very high
.
Ferrites
 are made by
sintering powders
consisting of a mixture
of ferric oxide and the
oxides of other metals
like 
lithium
, 
nickel
 
and
manganese
.
 
Their hysteresis loop is almost 
rectangular
[Fig.) which enables these to be used for
memory circuit 
in 
computers
.
 These have a 
high electrical resistivity 
unlike
the 
ferromagnetic materials 
which are very
good conductors
.
So 
ferrites
 are widely used in the manufacture
of components for 
Radio
 and 
electrical
communication
Slide Note
Embed
Share

Hysteresis curves play a crucial role in understanding the properties of ferromagnetic substances like soft iron and steel. The differences in retentivity, coercive force, permeability, and susceptibility between these materials impact their performance in electromagnets and transformer cores. The choice of magnetic materials, such as steel for permanent magnets and vicalloy for high coercivity, is essential for various applications in electromagnetism. Soft iron stands out as an ideal material for electromagnets due to its low hysteresis loss. Overall, selecting the right material based on hysteresis characteristics is vital for efficient operation in electromagnetic devices.


Uploaded on Jul 25, 2024 | 1 Views


Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

E N D

Presentation Transcript


  1. The importance of hysteresis curves

  2. The properties ferromagnetic substance obtained from the size and shape hysteresis loop. Fig. shows hysteresis loops for soft iron and steel. magnetic of a can be of the the

  3. The retentivity of soft iron (OC) is greater than that of steel (OC'). i.e., soft iron retains more magnetism than steel, when the magnetizing force is totally removed. The coercive force for soft iron (OD) is smaller than that for steel (OD ). ie. iron is more readily demagnetised than steel.

  4. the permeability = (BIH) for soft iron is greater than that for steel. The susceptibility = (MIH) for soft iron is greater than that for steel. The area of the B-H loop for steel is much larger than that for soft iron. Thus the energy loss per unit volume per cycle of magnetisation is greater for steel than that for soft iron.

  5. Choice of Magnetic materials. Permanent Magnets. Materials used for making magnets are never taken through a cycle. So hysteresis loss is a minor consideration in these cases. These materials should have high retentivity and high coercivity. So steel is a suitable material for permanent magnets. .

  6. Recently a number of alloys, having large values of coercivity have been developed for the purpose of construction of permanent magnets. The very suitable alloy of highest coercivity is named as vicalloy (vanadium, iron and alloy cobalt).

  7. Electro-magnets The material for the cores of electromagnets should have maximum flux density with comparatively small magnetising field and low hysteresis loss. Soft-iron is an electromagnets. ideal material for

  8. Transformer cores Materials diaphragms and chokes etc.. (which are meant for obtaining high magnetic flux) are frequently subjected to many cycles of magnetisation in one second. So the material selected for the purpose must be associated with high magnetic induction and low hysteresis loss. for transformer cores, telephone

  9. Soft-iron is better than steel for these purposes. By alloying soft-iron transformer steel is produced. It has a higher initial permeability and is an ideal material for cores of transformers. Alloys of iron and nickel, called permalloys have also very large initial permeabilities with 4% silicon,

  10. Ferrites Their very high. Ferrites are made by sintering consisting of a mixture of ferric oxide and the oxides of other metals like lithium, nickel and manganese. permeability is powders

  11. Their hysteresis loop is almost rectangular [Fig.) which enables these to be used for memory circuit in computers. These have a high electrical resistivity unlike the ferromagnetic materials which are very good conductors. So ferrites are widely used in the manufacture of components for Radio and electrical communication

More Related Content

giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#