同济大学：《大学物理》课程教学资源（电子教案，英文版）第十八章 物质的磁性

Magnetism in material

Magnetism in material

Agenda today 1.Paramagnetism and dimagnetism 2.Magnetization and Magnetic susceptibility 3.Ferromagnetism 4.Displacement current

Agenda today 1. Paramagnetism and dimagnetism 2. Magnetization and Magnetic susceptibility 3. Ferromagnetism 4. Displacement current

Paramagnetism (顺磁性) Atom magnetic moment 2nr T V 1=9= qv T2 29 2

Paramagnetism (顺磁性） Atom magnetic moment + - pm 

Magnetization and Magnetic Susceptibility (磁化强度与磁导率) In magnetic field,the direction of magnetic dipoles have the tendency to align to applied field M m Magnetization

Magnetization and Magnetic Susceptibility （磁化强度与磁导率） IO M B IS In magnetic field, the direction of magnetic dipoles have the tendency to align to applied field V p M m      Magnetization

The result of magnetization is equivalent to a current on the surface of the material,called an amperian current(表面电流) Density ofAmperian current Amperian current per unit length △V J

The result of magnetization is equivalent to a current on the surface of the material, called an amperian current（表面电流） Density of Amperian current Is l M s m s j lS j lS V p M        Amperian current per unit length

By ampere's law The magnetic field produced by amperian current is: Bi =Hoj=LoM The magnetic field in the material is B Bo Bod4 The magnetization is proportional to the applied field

By ampere’s law The magnetic field produced by amperian current is: The magnetic field in the material is The magnetization is proportional to the applied field

BH M= Where x is called the susceptibility of the material(磁化率)and H is called the magnetic field intensity of the applied field..(磁场强度) B+20 Where u is called the permeability of the material

Where  is called the susceptibility of the material （磁化率）and H is called the magnetic field intensity of the applied field.（磁场强度） Where  is called the permeability of the material

说 M-RPE M. 3 kT Bapp B M=C pp 居里定律 T

T B M C app  居里定律

For paramagnetic material: B-Bapp X>0 For diamagnetic material: B<Bapp X≤0 Ampere's law for magnetic material 5Aa=∑ Where I is the conducting current through the loop

For paramagnetic material: B>Bapp >0 For diamagnetic material: B<Bapp <0 Ampere’s law for magnetic material  H dl I L   Where I is the conducting current through the loop

Diamagnetic material抗磁性 B For atoms have no net magnetic moment

Diamagnetic material 抗磁性 f   m B m  + - v  B + - v  m   m f  For atoms have no net magnetic moment