Physics: Heat and Thermodynamics: UPSC Previous Year Questions (Science and Technology)
1 previous year UPSC Prelims question on Physics: Heat and Thermodynamics (Science and Technology). Choose an option to see the answer and explanation.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
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UPSC 2002Science and Technology · Physics: Heat and Thermodynamics
Q1. A hollow sphere of radius R, a hollow cube of side R and a thin circular plate of radius R, made up of the same material, are all heated to 20°C above room temperature. When left to cool in the room, which of them will reach the room temperature first?
Explanation
The rate at which an object cools depends on its surface area-to-volume ratio and temperature difference with the surroundings. A higher surface area-to-volume ratio allows more heat to be dissipated into the surroundings, leading to faster cooling. The sphere has the largest surface area compared to the cube and circular plate. The larger the surface area, the more heat can be radiated or transferred to the surroundings, which leads to a faster cooling rate. The sphere cools faster than the circular plate and cube for the same radius. The more heat the sphere can radiate, the quicker it will reach room temperature compared to objects with smaller surface areas. Note: Here, we can ignore the impact of volume as the sphere, disc or cube all are hollow with negligible thickness.
Answer key for these questions
Q
UPSC year
Correct answer
1
2002
(c) Sphere
Frequently asked questions
How many previous year UPSC questions are there on Physics: Heat and Thermodynamics?
This page covers 1 previous year UPSC Prelims GS Paper-I questions on Physics: Heat and Thermodynamics (Science and Technology), asked from 1999 to 2003. Each has the correct answer and an explanation.
How should I use previous year UPSC questions for Prelims?
Attempt each question first, then open the answer and read the explanation for every option. Repeat by chapter, and track which statements UPSC reuses across years. Previous year questions show the exam pattern and difficulty level.
Which years are covered for Physics: Heat and Thermodynamics?
Questions on Physics: Heat and Thermodynamics (Science and Technology) are available for 4 years, from 1999 to 2003. Use the Year filter to practise a single paper.
