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Q12 (CDS-II/2017) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

Two wires are made having same length I and area of cross-section A. Wire 1 is made of copper and wire 2 is made of aluminium. It is given that the electrical conductivity of copper is more than that of aluminium. In this context, which one of the following statements is correct?

Result
Your answer: —  ·  Correct: B
Explanation

The resistance (R) of a conductor is determined by the formula R = ρ(l/A), where ρ is the resistivity, l is the length, and A is the cross-sectional area [1]. Resistivity (ρ) is the reciprocal of electrical conductivity (σ), meaning materials with higher conductivity have lower resistivity. The problem states that both wires have the same length (l) and area (A), and that copper has a higher electrical conductivity than aluminium. Consequently, copper (wire 1) has a lower resistivity than aluminium (wire 2). Since resistance is directly proportional to resistivity when dimensions are constant, the wire with the higher resistivity (aluminium) will have a higher resistance [1]. Therefore, the resistance of wire 2 (aluminium) will be higher than that of wire 1 (copper). Power dissipation (P = I²R) would also be higher in wire 2 if the same current were applied [2].

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Activity 11.3 > p. 178
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
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