Lecture 9 Flashcards
Give the equation for the magnetic flux density in free space
B = magnetic flux density
µ0 = permeability of free space
H = magnetic field strength
What are the 2 origins of a net magnetisation
- Spontaneous
- Applied magnetic field induces magnetic moments
Give the equation for the magnetic flux density inside a material
B = magnetic flux density
µ0 = permeability of free space
H = magnetic field strength
M = magnetisation
Give the equation for the magnetic flux density inside a material due to an applied magnetic flux density
B = magnetic flux density
B_appl = applied magnetic flux density
M = magnetisation
Give the equation for the magnetic susceptibility of a material
χ = magnetic susceptibility
What is diamagnetism?
A behaviour that occurs in all material: an applied magnetic field induces a magnetic moment if the opposite direction to that field.
What is paramagnetism?
A behaviour that occurs in materials with pre-existing magnetic moment: an applied field induces magnetic moments in the same direction as the field.
What is ferromagnetism?
The most important ordered magnetic state: in ferromagnetic materials the magnetic moments are spontaneously aligned parallel to one another.
Describe the shape of the M-H curve for hard magnetic materials
Are permanent magnets hard or soft magnetic materials?
Hard
Hard ferromagnetic have a large __ and __.
M_r
H_c
Describe the shape of the M-H curve for soft magnetic materials
Are transformer cores hard or soft magnetic materials?
Soft
Soft ferromagnetic have a large ___________, small __ and small __.
Susceptibility
M_r
H_c
