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Name: Vishnu
Status: student
Grade: other
Location: VA



Question:
What are the properties (in terms of structure) of Nichrome wire that makes it perfect for resistance investigations?


Replies:
Hi Vishnu,

I am not at all sure what you mean by "resistance investigations", but Nichrome wire is far from perfect for use in resistance measurement. The main attribute of Nichrome is that, like Kantal and other similar alloys, Nichrome can withstand very high temperatures without oxidation. Therefore it is an excellent material to make electrical heating elements from, that must operate at red-heat. Nichrome's resistance increases substantially, as its temperature increases, which makes it relatively useless for making precision resistance devices.

The main attribute needed in making accurate resistors is that the resistance of the wire used to make the device, must not significantly change over temperature. After all, what use is a resistance measurement "standard", against which you are comparing unknown resistances, if the "standard" resistor changes it resistance as temperature changes.

Two alloys that maintain a constant resistivity over a wide temperature range, and which are commonly to make wire used in making resistors, and "shunts" (low-value resistors that are part of an ammeter) are Constantin and Cupron.

Regards,
Bob Wilson.



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