Free Thermodynamics MCQs with Answers
714 Thermodynamics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermal equilibrium and heat explain how temperature and energy transfer are related, while molar specific heats describe the heat required by a gas at constant volume or constant pressure. The first law connects heat supplied, work done and change in internal energy, with sign conventions kept distinct from temperature changes.
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Read the Thermodynamics notesFree MDCAT chapter notes with key terms714 questions · page 19 of 36
- A. 46°
- B. -40°
- C. 32°
- D. 40°
Explanation: Fahrenheit and Celsius scales have the same reading at -40°. This is the point where the numerical value in Fahrenheit is equal to the…
Correct answer: -40°- A. Temperature of source
- B. Temperature of sink
- C. Both a and b
- D. Working substance
Explanation: The efficiency of a heat engine depends on both the temperature of the source (where heat is absorbed) and the temperature of the sink…
Correct answer: Both a and b- A. Input stroke
- B. Exhaust stroke
- C. Power stroke
- D. All of these
Explanation: The third stroke of a petrol engine is the power stroke. It is the stage where the ignited fuel-air mixture expands, exerting force on the…
Correct answer: Power stroke- A. 25% to 30%
- B. 30% to 35%
- C. 35% to 40%
- D. 30% to 40%
Explanation: The typical efficiency range for a diesel engine is between 35% and 40%.
Correct answer: 35% to 40%- A. JK
- B. J^-1K
- C. JK^-¹
- D. J^-1K^-¹
Explanation: The unit of entropy is joules per kelvin (J^-1K^-¹). Entropy is a measure of the amount of energy in a system that is unavailable to do…
Correct answer: J^-1K^-¹- A. Adiabatic process
- B. Isobaric process
- C. Isothermal process
- D. Isochoric process
Explanation: In an isochoric (constant volume) process, there is no change in volume, and thus no work is done by or on the system.
Correct answer: Isochoric process- A. Increases
- B. Decreases
- C. Remains the same
- D. 0
Explanation: Entropy is a measure of the disorder or randomness of a system. When heat is removed from the system, the disorder decreases, leading to a…
Correct answer: Decreases- A. Irreversible
- B. Reversible
- C. Either a or b
- D. Cyclic
Explanation: An irreversible process is one that cannot be retraced or undone. In such processes, entropy always increases and the system and…
Correct answer: Irreversible- A. 273.16 K
- B. 273.16°F
- C. 273.16°C
- D. 270°C
Explanation: The triple point of water is the temperature and pressure at which water can coexist in all three phases: solid, liquid, and vapor.
Correct answer: 273.16°C- A. Petrol engine
- B. Carnot engine
- C. Diesel engine
- D. Watt's steam engine
Explanation: The Carnot engine has the highest theoretical efficiency among heat engines operating between two temperature reservoirs.
Correct answer: Carnot engine- A. Depends upon T and Ta
- B. Depends upon the working substance
- C. Is 100% if T2 =0K
- D. None of these
Explanation: The efficiency of the Carnot engine depends only on the temperatures of the hot and cold reservoirs, T and Ta , respectively.
Correct answer: None of these- A. Fahrenheit
- B. Centigrade
- C. Kelvin
- D. None
Explanation: The Kelvin scale is an absolute temperature scale that is independent of the properties of any specific substance.
Correct answer: Kelvin- A. 323 K
- B. 50 K
- C. 223 K
- D. 70 K
Explanation: The Kelvin temperature is obtained by adding 273.15 to the Celsius temperature. Therefore, 50°C + 273.15 = 323.15 K.
Correct answer: 323 K374. For which combination of working temperatures is the efficiency of Carnot's engine the highest?
- A. 100 K, 80 K
- B. 80 K, 60 K
- C. 40 K, 20 K
- D. 60 K, 40 K
Explanation: The efficiency of Carnot's engine depends on the temperature difference between the hot and cold reservoirs.
Correct answer: 100 K, 80 K- A. it is independent of nature of working substance
- B. it is linear over a wide range of temperature
- C. it is based on triple point of water
- D. none
Explanation: This is indeed the key advantage of the Kelvin scale. Unlike the Celsius and Fahrenheit scales, which are defined based on specific…
Correct answer: it is independent of nature of working substance- A. 1:2
- B. 2:3
- C. 3:4
- D. 8:9
Explanation: Here's how to solve this problem and find the ratio of their linear expansions:1.
Correct answer: 8:9- A. Air conditioner
- B. Desert cooler
- C. Room cooler
- D. Projector
Explanation: A desert cooler, also known as an evaporative cooler, is a device that uses the principle of evaporative cooling to lower the temperature…
Correct answer: Desert cooler- A. Absorbers
- B. Emitters
- C. Reflectors
- D. None of these
Explanation: White clothes are good reflectors of light and heat. This means that they reflect most of the sunlight that falls on them, rather than…
Correct answer: Reflectors- A. Increases
- B. Decreases
- C. Remains Same
- D. Decreases then suddenly increases
Explanation: When a system absorbs heat from its surroundings, it gains thermal energy.
Correct answer: Increases- A. 574
- B. 674
- C. 474
- D. 364
Explanation: The heat of vaporization is the amount of heat energy required to convert a unit mass of a substance from a liquid to a gas at its boiling…
Correct answer: 574