Special resistor materials: carbon, Physics

Carbon:

Atomic number

6

Symbol

C

Atomic weight

12.011

Discovery

Carbon exists free in nature and has been known since prehistoric time.

Electronic configuration

[He] 2S2 2p2

Word origin

Latin name carbo, French name carbon, coal or charcoal.

me n contact Melting point

34500C

Electrical resistivity

400-1200*10-8 ohm-m.

Properties:

1.      Carbon is found free in three forms: Amorphous, Graphite and Diamond.

2.      It has negative temperature coefficient of resistance.

3.      Its resistance is pressure sensitive. As pressure increases electrical resistance of the carbon emcontact decreases.

4.      It can withstand arcing.

5.      It has not a very good abrasive resistance.

6.      Diamond is one of the hardest substances with a high melting point and index of refraction.

Uses:

1. Carbon is used in applications like brushes for electrical machines electrodes for electric arc furnaces non wire resistors battery cell element are lamps are welding etc.

2. Carbon is also used in some telecommunication equipments like potentiometers microphones etc.

3. Diamond is prized as a gemstone and is used for cutting, drilling and as bearing.

4. Graphite is used as crucible for melting metal, in pencils, for rust protection, for lubrication, an as a moderator for showing down neutrons for atomic fission.

5. Amorphous carbon is used for removing tastes and odours.

Posted Date: 7/21/2012 7:50:24 AM | Location : United States







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