The document discusses hysteresis curves and their properties. It defines hysteresis as the lagging of magnetic induction behind the magnetizing field when a magnetic substance undergoes a complete magnetization cycle. A hysteresis loop graphs the relationship between magnetic flux density (B) and magnetizing force (H). It describes the key aspects of a hysteresis loop including coercivity, retentivity, and energy dissipation due to hysteresis. It also compares the hysteresis curves of steel and soft iron, noting their differences in properties. Finally, it outlines some applications that make use of hysteresis in ferromagnets.

1. (Principal Sir) (Subject Teacher)

2. ACKNOWLEDGEMENT

3. INDEX
I. CERTIFICATE OF EXCELLECNE
II. ACKNOWLEDGEMENT
III. AIM OF PROJECT
IV. INTRODUCTION
V. HYSTERISIS CURVE/LOOP
VI. COERCIVITY AND REMANENCE
VII. VARIATIONS IN HYSTERISIS CURVE
VIII.ENERGY DISSIPATION DUE TO HYSTERESIS
IX. HYSTERESIS CURVE FOR STEEL AND SOFT IRON CORE
X. APPLICATIONS
XI. BIBILIOGRAPHY

4. AIM OF THE PROJECT
To study the HYSTERISIS CURVE and its applications.

5. The lagging of intensity of magnetization (I) or magnetic
induction (B) behind magnetizing field (H), when a
specimen of a magnetic substance is taken through a
complete cycle of magnetization is called hysteresis.
A hysteresis loop shows the relationship between the
induced magnetic flux density (B) and the magnetizing
force (H). It is often referred to as the B-H loop.

6. Hysteresis loop
• To start with the iron core placed in a solenoid having
no current. Now current is flowing in the solenoid
increases gradually. This magnetic field is called
magnetizing field (H). As the value of H is increases
magnetic flux density (B) also increases. The variation
of B with H is shown by first curve. Further increase in
current in solenoid increases the value of H but not of
B. Thus point of saturation is obtained.
• Now ,reduce the value of current in the solenoid till
the value of H becomes zero.]The iron core placed
inside the solenoid begins to demagnetize. When H=0,
B not 0. It shows magnetic material retains magnetism
however if H is 0. This property is c/a retentivity

7. • Now reverse the direction of flow of electrons in
the solenoid, so that the H acts in opposite direction.
The magnetic field B of the magnetic material
decreases. The magnetic field B becomes 0. This
magnetizing field H needed to completely
demagnetize the material is called coercivity.
• The value of current in he solenoid is further increased
in the same direction, so the value of increases further.
The value of B also increases in the reverse direction i.e.,
along y axis. In other words, magnetic material begins to
magnetize in opposite direction till it is completely
magnetized. Now repeat above steps.

8. Coercivity andRemanence
When a ferromagnetic material is magnetized in one direction, it
will not relax back to zero magnetization when the imposed
magnetizing field is removed. The amount of magnetization it retains
at zero driving field is called its remanence.
It must be driven back to zero by a field in the opposite direction; the
amount of reverse driving field required to demagnetize it is called its
coercivity.

9. Variations in Hysteresis Curves
There is considerable variation in the hysteresis of different magnetic materials.

10. ENERGY DISSIPATION DUE TO
HYSTERESIS
During the cycle of magnetization and demagnetization of
magnetic substance, energy is spent. This energy appears
as the heat in the substance. Such energy loss is known as
the hysteresis loss. The loss of energy per unit volume of
the substance is equal to the area of B-H curve.
The study of hysteresis curve of a given substance helps us
to know different properties of substance. For instance
form hysteresis curve of a given material its retentivity,
coercivity, susceptibility, permeability and energy loss per
cycle of magnetization can be calculated.

11. HYSTERESIS CURVE FOR STEEL AND
SOFT IRON CORE
i. The retentivity of soft iron is
more than the retentivity of steel
ii. Coercivity of soft iron is less
than the coercivity of steel
iii. Soft iron can be easily
demagnetize as compared to
steel
iv. Area of loop for iron is less then
the area of steel, therefore
hysteresis loss in case of steel
is greater than soft iron core

12. APPLCATIONS
• There are a great variety of applications of the hysteresis in
ferromagnets. Many of these make use of their ability to retain a
memory, for example magnetic tape, hard disks, and credit cards. In
these applications, hard magnets (high coercivity) like iron are
desirable so the memory is not easily erased.
• Soft magnets (low coercivity) are used as cores in electromagnets.
The nonlinear response of the magnetic moment to a magnetic field
boosts the response of the coil wrapped around it. The low coercivity
reduces that energy loss associated with hysteresis.
• In neuroscience some neurons do not return to their basal
conditions from a stimulated condition immediately after removal of
the stimulus is an example of hysteresis.

13. BIBILIOGRAHY
1. WWW.GOOGLE.COM
2. WWW.SCRBID.COM
3. NCERT 12
4. DINESH MILLENNIUM PHYSICS -XII