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Q1 (NDA-I/2018) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Thermal physics Answer Verified

Which one of the following statements is correct ?

Result
Your answer: —  Â·  Correct: A
Explanation

In thermodynamics, heat is strictly defined as the form of energy that is transferred between systems or objects solely by virtue of a temperature difference. If energy is transferred through other means, such as mechanical work or pressure changes, it is not classified as heat. A temperature difference is the fundamental prerequisite for heat transmission; without it, net heat transfer between two bodies is impossible. While all three modes of heat transfer—conduction, convection, and radiation—require a temperature gradient to occur, heat is not the only way energy can be transferred; work is a distinct method of energy transfer. Furthermore, heating typically causes thermal expansion, meaning the length and volume of an object do not remain exactly the same. Therefore, any energy transfer not involving a temperature difference is, by definition, not heat.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > Activity 7.3: Let us fi nd out > p. 94
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