SSC
The term 'Zeroth Law of Thermodynamics' was coined in 1931 by:
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Answer: Option A — Ralph H. Fowler
Detailed Solution
Fowler. The Zeroth Law of Thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. Thermal equilibrium means that there is no net flow of heat between the systems when they are in contact, because they are at the same temperature.
This law makes the concept of temperature meaningful. It is the reason a thermometer works: when a thermometer (the third system) is in thermal equilibrium with a body, it shows the body's temperature, and two bodies showing the same reading on the thermometer are at the same temperature.
The first, second and third laws of thermodynamics had already been formulated in the 19th and early 20th centuries. Later, scientists realised that the principle of thermal equilibrium was even more fundamental and should come before the others logically. Since the numbers "first", "second" and "third" were already taken, the British physicist Ralph Howard Fowler (1889-1944) called it the "zeroth law" around 1931. Fowler was a mathematical physicist at Cambridge and was the doctoral supervisor of several famous scientists, including Paul Dirac and Subrahmanyan Chandrasekhar.
The laws of thermodynamics in brief:
- Zeroth law: defines thermal equilibrium and temperature.
- First law: energy can neither be created nor destroyed; heat supplied to a system equals the increase in its internal energy plus the work done by it (conservation of energy).
Second law: heat cannot flow by itself from a colder body to a hotter one; no heat engine can be 100% efficient; the entropy of an isolated system never decreases. It was formulated by Rudolf Clausius and Lord Kelvin.
Third law: the entropy of a perfect crystal approaches zero as its temperature approaches absolute zero (0 K or –273.15°C), which cannot be reached in a finite number of steps. It was developed by Walther Nernst.
Why not the other options?
- ✗Rudolf Clausius formulated the second law and introduced the concept of entropy.
- ✗Lord Kelvin gave the absolute temperature scale and a statement of the second law.
- ✗Sadi Carnot studied the efficiency of heat engines (the Carnot cycle, 1824).
Quick tip
Remember: Zeroth law = thermal equilibrium and temperature (named by R.H. Fowler, about 1931); 1st = energy conservation; 2nd = entropy (Clausius, Kelvin); 3rd = absolute zero (Nernst).
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Heat & Thermodynamics — Preparation
This question tests your understanding of Heat & Thermodynamics, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers heat and temperature, temperature scales and conversions, thermometers, thermal expansion, specific heat and latent heat, the transfer of heat by conduction, convection and radiation, and the basic laws of thermodynamics. Questions commonly ask about the temperature at which the Celsius and Fahrenheit scales read the same (-40 degrees), why water is used in car radiators (high specific heat), how heat reaches us from the Sun (radiation), and why we feel cold after sweating (cooling by evaporation). Practise converting between Celsius, Fahrenheit and Kelvin. Practise the heat and thermodynamics questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.