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QPage 11: Q3: HC Verma: Concepts of Physics - Volume 2 Heat and Temperature Page 11: Q3 Solution: It is said that mercury is used in defining the temperature…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often assume mercury’s expansion is inherently uniform, overlooking that “uniform” is defined only after an independent temperature scale exists; first establish a scale (e.g., ideal‑gas law) and then verify linearity, rather than using the expansion to define the scale itself.

It is said that mercury is used in defining the temperature scale because it expands uniformly with temperature. If the temperature scale is not yet defined, is it logical to say that a substance expands uniformly with temperature?

Step-by-Step Verified Solution

**Answer:** No, it is not logical to say a substance expands uniformly with temperature before the temperature scale is defined. **Step-by-Step Explanation:** The statement is circular: if temperature is defined by the expansion of mercury, then saying mercury expands uniformly with temperature is a tautology. Historically, mercury was chosen because its expansion is approximately linear with the ideal gas temperature scale, which is defined independently via P∝TP \propto T at constant volume. Without an independent temperature scale, "uniform expansion" has no physical meaning.

All Questions in this Chapter

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