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Q74 (CDS-I/2005) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

Consider the following statements: Copper rods are generally preferred to iron rods for making lightning conductors because 1. Copper is a better conductor of electricity than iron. 2. Copper is not easily oxidised under atmospheric conditions. 3. Copper is cheaper and easily available as compared to iron. 4. Specific heat of copper is more than that of iron. Which of the statements given above are correct ?

Result
Your answer: —  Â·  Correct: A
Explanation

Copper is preferred over iron for lightning conductors primarily due to its superior electrical conductivity and corrosion resistance. Copper is one of the best electrical conductors, with conductivity significantly higher than iron, allowing it to carry high lightning currents with minimal resistance and heat generation [t1, c4]. Furthermore, while iron rusts and flakes when exposed to moist air, copper is more resistant to atmospheric oxidation [c3, c5]. Although copper reacts slowly to form a green basic copper carbonate layer, it does not deteriorate as rapidly as iron, ensuring long-term durability [c3, t2]. Statement 3 is incorrect because copper is significantly more expensive than iron [t2, t4]. Statement 4 is also incorrect as the specific heat of copper (approx. 0.385 J/g°C) is actually lower than that of iron (approx. 0.450 J/g°C). Thus, only statements 1 and 2 are correct.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 3: Electricity: Circuits and their Components > 3.2 A Simple Electrical Circuit > p. 36
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.5 CORROSION > p. 53
  3. [3] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > 1.3.1 Corrosion > p. 13
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