STERILITY TESTING OF PHARMACEUTICALS ppt by DR.C.P.PRINCE
Final hysterisis loop
1. CONTENTS
• What are ferromagnetic materials?
• What is B-H curve?
• Magnetic hysteresis
• Hysteresis loop
• Saturation magnetization
• Retentivity
• Coercivity
• Soft and hard materials
2. FERROMAGNETIC
MATERIALS
• Ferromagnetic materials, such as iron,
contain unpaired electrons(domains),
each with a small magnetic field of its
own, that align readily with each other in
response to an external magnetic field.
This alignment tends to persists even
after the magnetic field is removed.
3. What is B-H curve?
• The BH Curve is a plot of the Magnetic
Flux Density(B) vs Magnetic Field
Strength(H).
• The curve tells us about the change in
the Flux density of a material as the
magnetic field strength(H) is increased.
• This is an important curve in selecting
materials for electric machines.
• It is also called Hysteresis loop.
4. MAGNETIC HYSTERESIS
• Magnetic hysteresis is a characteristic of
ferromagnetic materials, consisting of the
lack of retraceability of the initial
magnetization curve when the magnetic field
is relaxed.
• If we increase either the current or the
number of turns we can increase the
magnetic field strength ( H).
6. SATURATION
MAGNETIZATION
• As long as value of H is small, most of the
atoms , due to strong bonding do not respond
to the external magnetic field. But the atoms
near the boundary start shifting .If we still go
on increasing the value of H ultimately all the
domains arrange in one direction which we
call saturation magnetization.
7.
8. RETENTIVITY
• The electromagnetic core material still retains
some of its magnetism even when the current
has stopped flowing in the coil.
• This ability for a coil to retain some of its
magnetism after the magnetization process
has stopped is called Retentivity i.e. value of B
when H=0.
9. • Some ferromagnetic materials have a high
retentivity (magnetically hard) making them
excellent for producing permanent magnets.
Example :Alnico
• While other ferromagnetic materials have
low retentivity (magnetically soft) making
them ideal for use in electromagnets OR
solenoids . Example: soft iron
10. COERCIVITY
• When we reverse the direction of the current
flowing through the coil, thereby making the
value of H, the magnetic field strength,
negative.
• This effect is called Coercive Force .
11. • Some ferromagnetic materials have a high
retentivity (magnetically hard) while other
ferromagnetic materials have low retentivity
(magnetically soft).
