NCERT Exercise 11.1 — Q18 - Electricity
Question: Explain the following. (a) Why is the tungsten used almost exclusively for filament of electric lamps? (b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal? (c) Why is the series arrangement not used for domestic circuits? (d) How does the resistance of a wire vary with its area of cross-section? (e) Why are copper and aluminium wires usually employed for electricity transmission?
Answer: (a) Tungsten has a very high melting point and can glow at high temperature without melting. (b) Alloys have higher resistivity and do not oxidise easily at high temperatures. (c) In series, all ap...
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