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Eureka is a commercial name of a heating element whose composition is:
1. 70% iron, 25% chromium, 5% aluminium
2. 55% copper and 45% nickel
3. 80% nickel and 20% chromium
4. 45% copper and 55% nickel

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Correct Answer - Option 2 : 55% copper and 45% nickel

Eureka:

  • Constantan is a Nickel-Copper alloy also known as Eureka.
  • It usually consists of 55% copper and 45% nickel.
  • Its main feature is the low thermal variation of its resistivity, which is constant over a wide range of temperatures
  • Constantan is a Nickel-Copper-based alloy wire that has a high resistivity and is mainly used for thermocouples and electrical resistance heating.
  • It has a constant resistivity over a wide range of temperatures.
     

Composition:

  • Ni = 45 %
  • Cu = 55 %
     

Properties of Eureka:

  • Resistivity - 490 µΩ -cm
  • Melting point: 1300 ⁰C
  • Specific gravity: 8.9 gm /cm3
  • Negligible temperature Coefficient
  • Easily ductile
  • Resistant to atmospheric corrosion
  • Can be easily soldered and moulded
     

Application:

  • It is used for the measurement of temperature.
  • It is used for the formation of thermocouple, along with the wires of other metals such as copper, iron, and chromium.
  • It is especially used for resistance purposes since its resistance does not change much with the change in its temperature. It is used for DC current shunts. 

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