Does a thermometer measure its own temperature or the temperature of its surroundings? Explain.
Answer to Problem 1FTD
Explanation of Solution
The principle of working of thermometer is actually based on the expansion of mercury in temperature. When mercury is allowed to heat it undergoes expansion. The mercury expands until it is in thermal equilibrium with heat of radiation which is in contact. The thermometer calibrated to measure that temperature.
If a thermometer is placed in sun radiation the mercury absorbs that radiation and expands until it is in thermal equilibrium. Therefore it shows a greater temperature than the air temperature. Therefore thermometer measures the temperature of the mercury rather than temperature of the surroundings.
Conclusion:
Thus, a thermometer measures its own temperature rather than surrounding temperature.
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