GROUP 4: MAGNETIZATION
CURVE & THE HYSTERESIS
LOOP
PRESENTED BY:
Catherine Ndovi BEEE/23/SS/015
McMillan Chiwasa BEEE/24/ME/001
Fazili Saidi BEEE/23/SS/017
Lemson Mpokwa BEEE/23/SS/011
Jubeda Orleen Ntaukira BECE/23/SS/010
Rachel Yankho Mzinganjira BECE/23/SS/009
Takuda Sean Matare BECE2/23/SS/012
HOW MATERIALS RESPOND TO MAGNETIC FIELD
•A Material’s response to the presence of a magnetic field depends on
their magnetic properties.
•Magnetism arises from the interaction between electrons in an atom.
Electron spin and orbital motion contribute to the atomic magnetic
moment.
•Magnetic moment refers to the measure of the strength and orientation
of an atom’s magnetic field. It’s a vector quantity.
CONT..
• Electrons spinning generates a magnetic moment similar to that of a
tiny bar magnet. Orbital motion of electrons around the nucleus also
generates a magnetic moment.
• The combination of the two results in atomic magnetic moment.
TYPES OF MAGNETIC RESPONSES
Diamagnetic response.
• Weakly repelled by a magnet
• Weakly magnetized in the opposite direction of the magnetic field.
• Repulsion of magnetic lines of force from the Centre of the material.
• Have no unpaired electrons.
• They are in solid, liquid and gaseous state e.g. Copper, Mercury, Gold, water and
Hydrogen.
TYPES OF MAGNETIC RESPONSES CONT..
Paramagnetic response
• Weakly attracted by the magnet.
• Weakly magnetized in the same direction of the
magnetic field.
• Magnetic lines of force attracted towards the
Centre of the material.
• Lose magnetism upon the removal of the
external magnetic field.
• Have unpaired electrons. They are in all states
e.g. Aluminum, platinum, Sodium and crown
glass.
TYPES OF MAGNETIC RESPONSES CONT..
Ferromagnetic response
• Strongly attracted by a magnet.
• Strongly magnetized in the same direction of the magnetic field.
• Strong attraction of magnetic lines of force towards the Centre of the material.
• Retain magnetism on removal of external magnetic field i.e. permanent magnets.
• Have unpaired electrons and are only in solid state e.g. Iron, Nickel and Cobalt.
HYSTERESIS LOOP
Hysteresis occurs in magnetic materials when
the magnetization (B) lags behind the applied
magnetic field (H). Common materials exhibiting
hysteresis include iron, nickel, cobalt, and their
alloys. These materials are widely used in electrical
engineering due to their ability
to retain magnetization
The hysteresis loop illustrates the lag or delay
in the response of the material's magnetization
to changes in the external magnetic field, which
is the fundamental concept of hysteresis.
he hysteresis loop illustrates the lag or delay in the response of the material's magnetization to changes in the external magnetic
field, which is the fundamental concept of hysteresis.
ANALYSIS
⮚ When magnetic field strength (H) is increased from zero, the magnetic flux density
(B) increases. As the magnetic field is increased, the value of magnetism rises until
it hits point A, which is known as the saturation point, where B remains constant.
With a drop in the value of the magnetic field, there is a decrease in the value of
magnetism. However, when B and H are both zero, the substance or material
retains some magnetic, which is known as retentivity or residual magnetism. When
there is a reduction in the magnetic field towards the negative side, magnetism
likewise decreases. The material is entirely demagnetized at point C. The cycle is
repeated in the opposite direction, with the saturation point D, retentivity point E,
and coercive force F. The cycle is complete due to the forward and opposite
direction processes, and this cycle is known as the hysteresis loop.
CONT….
⮚ Coercive force - is the amount of force necessary to eliminate a material’s
retentivity (C).
⮚ Saturation – Maximum alignment of magnetic domains. The point where further
increases in H do not significantly increase B.
⮚ Retentivity – Residual magnetization after removing H.
⮚ Coercivity – Reverse H required to demagnetize the material.
⮚ Negative Saturation– Complete reversal of magnetization.
⮚ The area within the loop indicates energy loss due to hysteresis.
FACTORS AFFECTING THE HYSTERESIS
LOOP
MATERIAL COMPOSITION
● Hysteresis materials have short loops which indicate low coercivity and
retentivity.
● Perfect for applications for simple magnetization and demagnetization e.g
transformer core
FACTORS AFFECTING THE HYSTERESIS LOOP
CONT….
TEMPERATURE
● Thermal agitation causes the alignment of magnetic domains to be disrupted
as temperature rises.
● Results in a drop in saturation magnetization
STRENGTH OF MAGNETIC FIELD
● Applied magnetic field increases the strength of magnetized material.
● Increases the saturation hence increasing field strength
MECHANICAL STRESS
● Alters the alignment of magnetic domains
IMPORTANCE OF MAGNETIC HYSTERESIS IN ELECTRICAL APPLICATIONS
Kindel Media, 2021 Pixabay, 2017 Andre Moura, 2019
IMPORTANCE OF MAGNETIC HYSTERESIS IN
ELECTRICAL APPLICATIONS
Soft Ferromagnetic Materials Hard Ferromagnetic Materials
● Materials that have a small ● Materials that have a large amount
amount of magnetic retention. of magnetic retention.
(Electrical4U, 2024) ● They have a wide B/H
● They have a narrow B/H curve. curve(Electrical4U, 2024)
IMPORTANCE OF HYSTERESIS LOOPS IN MATERIAL
SELECTION
Transformer cores
• Understanding hysteresis helps to increase efficiency in transformers and motors
since hysteresis loss through heat, caused by alternating magnetic fields, is
avoided. Materials with narrow hysteresis loops would be optimal. This is to say, a
material with high permeability and low coercivity, like a soft iron core is preferred.
Permanent magnets
• Materials for permanent magnets are to have a high retentivity or remanence.
This information is provided by the hysteresis loop. This means, a high coercivity
like that of neodymium and Alnico would be required. Using the right material for
a permanent magnet means making a more efficient as machine cores.
IMPORTANCE OF HYSTERESIS LOOPS IN MATERIAL
SELECTION
Enhancing stability in control systems (Circuits for delays and
switches)
• The presence of hysteresis causes a delay between input and output response in a system,
this enables smooth transitioning of states thus avoiding rapid switching. For example,
electric heaters use thermostats, the working of these thermostats uses the principles of
hysteresis, when temperature drops below a certain level they turn on and vice versa. So,
without hysteresis the system might turn on and off rapidly thereby accelerating wear of
the appliance.
Magnetic memory storage devices
• In ferromagnets it is mostly used to retain memory in storage devices. This is mostly
influenced by a material’s retentivity and coercivity so that the device does not easily
demagnetize and lose data.
REFERENCES
Bertotti, g. (1998). Hysteresis in magnetism for physicists,materials,scientists and engineers. Applications of hysteresis loop. (n.d.).
BrainKart. https://www.brainkart.com/article/Applications-of-hysteresis-loop_38455/
Byjus Admin. (2023, August 28). Hysteresis - definition, meaning, hysteresis loop, loss and curve. BYJUS. https://byjus.com/jee/hysteresis/
Electrical4U. (2024, May 25). Hysteresis Loop: What is it (And What is its Significance)?. https://www.electrical4u.com/hysteresis-loop/
GeeksforGeeks. (2024, April 22). Hysteresis loop. GeeksforGeeks. https://www.geeksforgeeks.org/explain-hysteresis-loop/
(2024, April 22). Retrieved from geeksforgeeks: https://www.geeksforgeeks.org/explain-hysteresis-loop/
Ignor, F. L , Nattermann, T , Porkrovsky, V. (February ,1998). Theory of hysteresis loop in ferromagnets. Texas A&M University.
Kindel Media. (2021). Photograph of Tesla car. https://www.pexels.com/photo/city-street-summer-industry-9800033/
Moura, A. (2019). Utility tower. https://www.pexels.com/photo/three-red-tower-speakers-373638/
Pixabay. (2017). Three red tower speakers. https://www.pexels.com/photo/three-red-tower-speakers-373638/
