Question:medium

Explain the following.
  1. Why is the tungsten used almost exclusively for filament of electric lamps?
  2. Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
  3. Why is the series arrangement not used for domestic circuits?
  4. How does the resistance of a wire vary with its area of cross-section?
  5. Why are copper and aluminium wires usually employed for electricity transmission?

Updated On: Jan 13, 2026
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Solution and Explanation

(a) Tungsten, an alloy with a very high melting point and high resistivity, resists burning at elevated temperatures.


(b) Alloys are used for electrical heating elements in devices like toasters and irons due to their higher resistivity compared to metals, which generates significant heat.


(c) In series circuits, voltage is divided, resulting in each component receiving a reduced voltage. This diminishes current, causing devices to overheat and malfunction. Consequently, series connections are avoided in domestic wiring.


(d) A wire's resistance (R) is inversely proportional to its cross-sectional area (A); increasing the cross-sectional area decreases resistance, and vice versa.


(e) Copper and aluminum, excellent conductors with low resistivity, are commonly employed for electricity transmission.

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