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Q40 (CDS-I/2015) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

Two pieces of conductor of same material and of equal length are connected in series with a cell. One of the two pieces has cross-sectional area double that of the other. Which one of the following statements is correct in this regard ?

Result
Your answer: —  ·  Correct: D
Explanation

When two conductors are connected in series, the electric current (I) remains the same through both components [2]. The resistance (R) of a conductor is given by R = ρL/A, where ρ is resistivity, L is length, and A is the cross-sectional area [1]. Since both pieces are of the same material and length, the conductor with the smaller cross-sectional area (the thinner one) will have a higher resistance [1]. According to Joule's Law of Heating, the heat produced (H) is given by H = I²Rt. Because the current (I) and time (t) are identical for both conductors in series, the heat produced is directly proportional to the resistance. Therefore, the thinner conductor, having higher resistance, will produce more heat than the thicker one [1].

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 > Solution > p. 185
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