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Q109 (CDS-I/2014) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Thermal physics Answer Verified

Two layers of a cloth of equal thickness provide warmer covering than a single layer of cloth with double the thickness. Why?

Result
Your answer: —  Â·  Correct: A
Explanation

Two layers of cloth provide better warmth than a single layer of double thickness primarily because they encapsulate a layer of air between them [1]. Air is a poor conductor of heat, meaning it acts as an effective thermal insulator [2]. While a single thick layer of fabric provides insulation based on its material properties, the additional air gap created between two separate layers significantly enhances the overall thermal resistance [1]. This trapped air layer minimizes heat transfer from the body to the colder surroundings by reducing conduction and preventing large-scale convection currents [1]. Consequently, the combination of the fabric's own insulation and the high thermal resistance of the still air layer between the two pieces of cloth results in superior heat retention compared to a single, continuous layer of the same total thickness [1].

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > 7.1 Conduction of Heat > p. 92
  2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > In a Nutshell > p. 101
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