Wednesday, 8 January 2020

Electric Conducting Material: Low Resistivity or High Conductivity of Material and Properties- Silver, Gold, Aluminium, Copper

Electric Conducting Material

Low Resistivity or High Conductivity of Material

  • The material which has low resistivity or high conductivity are very useful in electrical engineering for manufacturing electrical engineering machines or equipment’s. 
  • These material used as conductors for all kind of winding required in electrical machines, apparatus and devices. 
  • These material are also used as conductor in transmission and distribution of electrical energy.

Required Properties in Low Resistivity or High Conductivity Conducting Material
This following properties are required in high conductivity materials:

  1. It should highest possible conductivity (ideally zero).
  2. Least possible temperature coefficient of resistance (ideally zero).
  3. It should have high melting point.
  4. Requires high mechanical strength.
  5. Its ductility should high, so that can be drawn in the form of wire easily.
  6. High corrosion resistance (free from oxidation).
  7. Solder ability, so that can be soldered easily to join the conductors.
  8. Low cost.
  9. Long life or durable.
  10. High flexibility.
  • The above required properties varies with the purpose for which material is being used. The resistivity of metals  increase and depends on impurity whether metallic or non metallic
  • Even an impurity of low resistivity will increase the resistivity of metal. The reason behind this is that the addition of slight impurity creates imperfections in the crystal lattice which disturb the flow of electrons through metals. 

Conductivity of Materials
Conductivity of Materials

Silver (Ag) 

  • It is the best conductor of electricity. It is having highest conductivity. It has property that it is moldable and weldable. 
  •  It is very costly. This is its main draw back which limits its practical use in electrical machines /equipment. 
  • It is still used in precious equipment used for research where cost of equipment does not matter. 

  1. Resistivity : 1.58 µΩ -cm
  2. Temperature coefficient of resistance at 20oC: 0.0038/oC
  3.  Melting point: 962oC
  4. Specific gravity: 10.49 gm /cm3

Copper (Cu) 

  • The extensively used, high conductivity material as conductor for electrical machines or equipment, is copper. 
  • Malleability, weld ability and solder ability are most important properties of copper. 
  • Copper in pure form is having good conductivity. But the conductivity of standard grade copper is reduced due presence of impurities. 

  1. Resistivity : 1.68 µΩ -cm
  2. Temperature coefficient of resistance at 20oC: 0.00386 /oC
  3.  Melting point: 1085oC
  4. Specific gravity: 8.96gm /cm3

Gold (Au) 

  • Gold is a precious and costly metal. 
  • It is having good conductivity. 
  • Gold is having highest malleability and ductility among all metals. 
  • Due to high cost, its practical use is limited to precious instruments used for research. 

  1.  Resistivity : 2.21 µΩ -cm
  2. Temperature coefficient of resistance at 20oC: 0.0034 /oC
  3.  Melting point: 1064oC
  4. Specific gravity: 19.30gm /cm3

Aluminum (Al) 

  • Aluminum is an element which is a silver-white, light weight, soft, non-magnetic and ductile metal.
  • The main ore of aluminum is bauxite. Aluminum is the third most abundant element (after oxygen and silicon) and most abundant metal found in earth’s crust.  
  • Aluminum is having low density, high ductility, good corrosion resistance and good conductivity, which makes it suitable to use as electric conductor for transmission and distribution of electricity.

  1. Resistivity: 2.65 µΩ -cm
  2. Temperature coefficient of resistance at 20oC: 0.00429 /oC
  3. Melting point: 660oC
  4. Specific gravity: 2.70 gm /cm3


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