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# 6 電流與電阻

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## 6 電流與電阻

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6-1 電流、電流密度與漂移速度 6-2 電阻與電阻率

6-3 歐姆定律

6-4 半導體與超導體

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2 1

0

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J: A/m2

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d d

d d

d

### 

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mm/h 88

. 1 m/s

10 9

. 4

m electrons/

10 47

. 8

mass/mol mass/m atoms/mol

atoms/m or

7

3 28

3 3

ne v J

M n N

M N

n

d

A A

2 3

2 3

2 6

2

/ 10

7 . 6 /

/ 10

5 . 3 /

10 91

. 4 )

2 / (

m A

A i

J

m A

A i

J

m d

A

Cu Cu

Al Al

Al

Al

cu

### =1.8mm

i=17mA, ρ=9×103kg/m3,M=64×10-3

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Resistance

Resistivity

Conductivity

### 

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Figure 25.4

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UnFigure Page 824

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### Resistivity and temperature

• Resistivity depends on

temperature. See Figure 25.6 at the left.

• Table 25.2 shows some

temperature coefficients of resistivity.

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### Symbols for circuit diagrams

Table 25.4 shows the usual symbols used in circuit diagrams.

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### Resistors are color-coded for easy identification

• This resistor has a resistance of 5.7 kΩ with a tolerance of ±10%.

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0

0

0

### 

Cu: 293K 1.69x10-8

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d

d

2

2

### 

The effect of temperature

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eff d

eff

13

6

2

eff

14

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Ohm’s Law

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I-V curves

### conductor pn junction diode

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6-4 Semiconductors

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### 

2

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Superconductors

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More Maglev - magnetic levitation

http://web.mit.edu/physics/hudson/ResearchBackground.htm

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Maglev、MRI and Tevatron

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Power line and motor

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BCS Theory-The Cooper pairs

http://www.chm.bris.ac.uk/webprojects2000/igrant/hightctheory.html

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