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Why Nichrome is chosen over Tungsten for the heating element?
However, when choosing a material for a particular application, many different properties of materials are considered together (such as: melting point (MP), boiling point (BP), thermal conductivity, electrical resistivity, cost, etc.).
The heating element of an electric iron is made of Nichrome, an alloy of 80% nickel and 20% chromium, because it has relatively high resistance (At 20℃, Resistivity ρ = 1.1 x 10-6 Ωm) and does not oxidize and burn easily at high-temperature (high melting and boiling point). When it is heated for the first time, it forms a thin layer of chromium oxide, that makes it practically immune to oxidation. Also, it is cheaper than tungsten. These characteristics make it an ideal heating element.
On the other hand, Tungsten oxidizes very quickly in the presence of oxygen even at a temperature of a few hundred degrees centigrade (i.e at red hot temperatures), and eventually burns out unless protected from oxygen in the air by sealing in an inert gas atmosphere. Also, its resistivity is comparably low than nichrome (At 20℃, Resistivity ρ = 4.9 x 10-8 Ωm), and, it is more expensive than nichrome.
That's why Nichrome is chosen over Tungsten for the heating element.
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