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# 10 Magnetism of Matter 磁 性

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### 10 Magnetism of Matter 磁 性

How can a clay- walled kiln

reveal Earth’s magnetic field of the past?

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### 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

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The earth’s dipole field The mid-atlantic ridge

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### 10-1 Magnetic Materials

Diamagnetism ( 逆磁性 )

Paramagnetism ( 順磁性 )

Ferromagnetism ( 鐵磁 32-6 Diamagnetism性 )

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### 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。

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### 10-1.2.1 Curie’s Law

M

Magnetization

A magnetization curve for

potassium chromium sulfate

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### 10-1.3.1 Hysteresis ( 磁 滯 )

Residual Flux Density

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/ A

0 A

0

q d

E d B

E B

0 0

B

E

E ds d

dt B ds d

  dt

 

 

 

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/ A

0 A

0

q d

E d B

E B

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Magnetic dipole:

north/south pole

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### 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

 

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Flux 

enclose d

charge

enc

##  

0 0

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inductin) of

Law s

(Maxwell'

inductin) of

Law s

0

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.

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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

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enc enc

d d E

0 ,

0 0

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### 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

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### 10-3.3 Comets

What shapes the

curved dust tail of a comet?

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## 光壓 αR

2

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### 10-4 Polarization ( 偏 振 )

Polarized Light

The Plane of Polarization

Linear, Circular and Elliptical

polarization

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### Display

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10 Magnetism of Matter 磁 性 Electromagnetic Waves 電磁 波. How can a clay-walled kiln reveal

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