An electric iron uses a metallic alloy for its heating element.

PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity

Problem

An electric iron uses a metallic alloy for its heating element. (i) State any two desirable properties of a material suitable for making heating elements. (ii) The resistivity values of four substances at room temperature are: Copper: 1.7×10−8  Ω m1.7\times10^{-8}\;\Omega\,\text{m} Nichrome: 1.1×10−6  Ω m1.1\times10^{-6}\;\Omega\,\text{m} Aluminium: 2.8×10−8  Ω m2.8\times10^{-8}\;\Omega\,\text{m} Constantan: 4.9×10−7  Ω m4.9\times10^{-7}\;\Omega\,\text{m} Select the most suitable substance for the heating element and justify your choice with reference to the given data. (iii) Explain why alloys, rather than pure metals, are generally preferred for heating elements even when their resistivity is higher.

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