10 Magnetism of Matter 磁 性

10 Magnetism of Matter 磁 性

How can a clay- walled kiln

reveal Earth’s magnetic field of the past?

Sections

1.物質的磁性 Magnetism 2.麥斯威爾方程式

Maxwell’s Equations 3.電磁波

Electromagnetic Waves

4.偏振 Polarization

The earth’s dipole field The mid-atlantic ridge

The Magnetic field

of the Earth

10-1 Magnetic Materials

 Diamagnetism ( 逆磁性 )

 Paramagnetism ( 順磁性 )

 Ferromagnetism ( 鐵磁 32-6 Diamagnetism性 )

10-1.1 Diamagnetism

逆磁性材料產生之磁矩與外磁場逆向，

如外磁場非均勻，其將受到由強磁場區 到弱磁場區之斥力。

10-1.2 Paramagnetism

• 液態氧被吸在兩個磁極之間

• 順磁性材料產生之磁矩與外磁場順 向，如外磁場非均勻，其將受到由 弱磁場區到強磁場區之吸力。

10-1.2.1 Curie’s Law

M ：

Magnetization

A magnetization curve for

potassium chromium sulfate

10-1.3 Ferromagnetism

• 鎳的磁域 (magnetic domain)

10-1.3.1 Hysteresis ( 磁 滯 )

矯頑磁力coercive force

殘餘磁通密度

Residual Flux Density

10-2 Maxwell’s

Equations

10-2.1 _{線積分與面積分}

( 安培迴路和高斯 面 )

磁場環流量 ( 安培定律 ) 電場通量

電場環流量 ^{法拉第定律} 磁場通量

/ A

0 A

0

q d

E d B

E B



















  





0 0

B

E

E ds d

dt B ds d

  dt

   

  





 

 





高 斯 面

/ A

0 A

0

q d

E d B

E B

























10-2.2 Magnets and magnetic

flux ( 磁鐵和磁通量 )

Magnetic dipole:

north/south pole

10-2.3 Gauss’ Law for Magnetic Fields

The net

magnetic flux thru any

closed

Gaussian surface is zero.

/ A

0 A

0

q d

E

d B

E B

























10-2.4 Gauss’ Law for electric Fields

Flux 

enclose d

charge

q

A d E









 ^{ }

0 0





10-2.5 Induced

Magnetic Fields

inductin) of

Law s

(Maxwell'

inductin) of

Law s

(Faraday'

0





 



 





dt s d

d B

dt s d

d E

E B



 



 

3 ways to produce a magnetic field:

by an electric current, by a magnetic

material, and by induction.

Law) Maxwell

- (Ampere

+

Law) s

(Ampere'

0 0

0 0

E enc enc

dt i s d

d B

i s

d B













 







 

 

10-2.6 Ampere-Maxwell Law

induced B field induced E field

10-2.7 Displacement Current

enc enc

d d E

i i

s d B

dt i d

0 ,

0 0

+ 





 ^{ }

 

 

10-2.8 Maxwell’s

Equations

10-3 Electromagnetic Waves

The oscillating E and B Fields

A Most Curious Wave –The ether ( 以太 )

) sin(

) sin(

t kx

B B

t kx

E E

m m















Light  Electromagnetic Waves



Hertz ( 赫茲 )– Radio Waves



The Electromagnetic Spectrum



The Relative Sensitivity of Human eyes 430nm – 690nm

10-3.1 Characteristics

10-3.2 Maxwell’s

Rainbow

10-3.3 Comets

What shapes the

curved dust tail of a comet?

光壓 ^αR

10-4 Polarization ( 偏 振 )

The Plane of Polarization

Linear, Circular and Elliptical

polarization

偏振片

Polarization of Light

偏 振

與 太

陽 眼

鏡

10-4.1 Liquid Crystal - I

Liquid Crystal - II

Liquid Crystal - III

LCD –Liquid Crystal

Display