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Wednesday, 8 January 2020

Electric Conducting Material: High resistivity Or Low conductivity and Properties - Tungsten, Carbon, Nichrome, Manganin

Electric Conducting Material



High Resistivity Or Low Conductivity 
  • Materials having low conductivity or high resistivity  are very useful for some electrical engineering products and applications. 
  • To manufacture the filaments for incandescent lamp, heating elements for electric heaters and furnaces, space heaters and electric irons etc this materials are used.

Required Properties in High Resistivity or Low Conductivity Conducting Material
The properties are required in high resistivity or low conductivity conducting material are following-
  1. It should high resistivity.
  2. It should high melting point.
  3. High mechanical strength requires.
  4. It's ductility should high, so that can be drawn in the form of wire easily.
  5. It should high corrosion resistance mean free from oxidation.
  6. It' cost should be low.
  7. Long life or durable.
  8. High flexibility.

Some of Materials having High Resistivity or Low Conductivity are listed below

  1. Tungsten
  2. Carbon
  3. Nichrome or Brightray B
  4. Nichrome V or Brightray C
  5. Manganin


Tungsten


Tungsten Conductor
Tungsten Conductor

  • Tungsten is produced  from rare ores or from tungstic acids.
  • Some facts about tungsten are listed below-
  • It is very hard.
  • It's resistivity is twice to aluminum.
  • Tensile strength of tungsten is very high.
  • It can be drawn in the form of very thin wire.
  • In the presence of oxygen it oxidize very quickly. 
  • Can be used up to 2000 degree C in the atmosphere of inert gases (Nitrogen, Argon etc.) without oxidation.
Properties 
  1. Specific weight : 20 gm/cm3
  2. Resistivity : 5.28 µΩ -cm
  3. Temperature coefficient of resistance : 0.005 / oC
  4. Melting point : 3410oC
  5. Boiling point : 5900oC
  6. Thermal coefficient of expansion: 4.44 × 10-9 / oC

Uses of Tungsten
  1. For incandescent lamp used as filament.
  2. Also used electrode in X- ray tubes.
  3. The great hardness, high melting and boiling points make it suitable for use as electrical contact material in certain applications. 
  4. It is having high resistance for destructive forces produces during operation of electrical contacts.

Carbon
  • Carbon is widely used in electrical engineering. 
  • Electrical carbon materials are manufactured from graphite and other forms of carbon.

Properties 

  1. Resistivity : 1000 - 7000 µΩ - cm
  2. Temperature coefficient of resistance : - 0.0002 to - 0.0008 /oC
  3. Melting point : 3500oC
  4. Specific gravity : 2.1gm /cm3

Uses of Carbon

Carbon is having following applications in electrical Engineering

  1. Making pressure sensitive resistors which are useful in automatic voltage regulators.
  2. Manufacturing the carbon brushes, that are used in DC machines. These carbon brushes improve the commutation as well as reduce the wear and tear.
  3. It also used for making filament of incandescent lamp.
  4. To make the electrical contacts.
  5. For making resistors.
  6. Also used for making battery cell elements.
  7. Used for electric furnaces as Carbon electrodes.
  8. Arc lighting and welding electrodes.
  9. Component for vacuum valves and tubes.
  10.  For makings parts for telecommunication equipment.

Nichrome or Brightray B
Composition of Nichrome or Brightray B
Ni=60% + Cr=15% + Fe= 25%

Properties of Nichrome or Brightray B

  1. Resistivity : 1.10 µΩ -cm
  2. Temperature coefficient of resistance : 0.0002 /oC
  3. Melting point : 1350oC
  4. Specific gravity : 8.24 gm /cm3
  5. High resistance to oxidation

Uses of Nichrome or Brightray B

  1. Used in making tubular heaters and electric irons.

Nichrome V or Brightray C

Composition of Nichrome V or Brightray C
Ni=80% + Cr=20%

Properties of Nichrome V or Brightray C

  1. Resistivity : 40 µΩ - cm
  2. Temperature coefficient of resistance : 0.0001 /oC
  3. Melting point : 1400oC
  4. Specific gravity : 8.4gm /cm3
  5. High resistance to oxidation

Uses of Nichrome V or Brightray C

  1. Used in making heating elements for electric heaters and furnaces.

Manganin

Composition of Manganin
Cu=84% + Mn=12% + Ni=4%

Properties of Manganin

  1. Resistivity : 40 µΩ -cm
  2. Temperature coefficient of resistance : 0.0001 /oC
  3.  Melting point : 1400oC
  4. Specific gravity : 8.4gm /cm3
  5. High resistance to oxidation

Uses of Manganin

Manganin is having following applications in electrical Engineering.

  1. Used in making electric heating elements and in electric furnaces.
  2. As the manganin is having very low temperature coefficient of resistance, therefore it is used to make the standard resistances and in measuring instruments.


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