Free First Law of Thermodynamics MCQs with Answers
297 First Law of 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.
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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297 questions · page 15 of 15
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: In the context of thermodynamics and gas behavior, an "isotherm" refers to a curve or line on a graph representing a process that occurs…
Correct answer: Option D- A. Adiabatic processes
- B. Isothermal process
- C. Cooling process
- D. First law of thermodynamics
Explanation: The burst of a tire is a sudden process. The process occurs instantaneously, such that the system does not get sufficient time to exchange…
Correct answer: Adiabatic processes- A. Q = W
- B. W = -U
- C. Q = -ΔU
- D. Q = ΔU + W
Explanation: An isothermal process is a thermodynamic process in which the temperature of a system remains constant.
Correct answer: Q = W- A. 50%
- B. 70%
- C. 90%
- D. 95%
Explanation: The efficiency of a Carnot engine is entirely a function of the temperatures of the hot and cold reservoirs you use.
Correct answer: 50%- A. Constant temperature
- B. Constant pressure
- C. Constant volume
- D. Constant temperature and constant pressure
Explanation: Isobaric process is a process in which the change in pressure is 0 i.e.
Correct answer: Constant pressure- A. Isothermal
- B. Isochronic
- C. Adiabatic
- D. Isobaric
Explanation: Isochronic or isochoric processes are carried out at constant volume.
Correct answer: Isochronic- A. Δθ = Δu + Δw
- B. Δθ = Δu
- C. Δθ = Δw
- D. None
Explanation: First law of thermodynamics states " energy can neither be created nor destroyed, it can only be altered/changed into different forms".
Correct answer: Δθ = Δu + Δw- A. Isobaric process
- B. Isothermal process
- C. Adiabatic process
- D. Isochor process
Explanation: Adiabatic is a process in which heat neither enters nor leaves a system, but the temperature of the system still changes.
Correct answer: Adiabatic process- A. The efficiency of the working substance
- B. The ideal gas scale temperature
- C. The thermal conductivity at the working substance
- D. None of the above
Explanation: The ratio of heat accepted to the heat rejected by a Carnot engine gives the efficiency of the working substance.
Correct answer: The efficiency of the working substance- A. Positive
- B. Negative
- C. Zero
- D. Constant
Explanation: Work is defined as the force applied over a distance, resulting in the displacement of an object.
Correct answer: Zero- A. Total internal energy has decreased
- B. The system has lost heat
- C. Work done by the system
- D. Work done on the system
Explanation: In the first law of thermodynamics, the expression for the change in internal energy of a system can be given as:∆U = Q - WIf the…
Correct answer: Work done by the system- A. isobaric process
- B. adlabalic process
- C. isothermal process
- D. isochoric process
Explanation: The adiabatic process is performed quickly when the system is perfectly insulated from the surrounding environment.
Correct answer: adlabalic process293. Which of the following makes the motion of a perpetual motion machine a physical impossibility?
- A. fist law of thermodynamics
- B. second law of thermodynamics
- C. third law of thermodynamics
- D. None of these
Explanation: As the second law of thermodynamics states, the more energy is transformed, the more is wasted.
Correct answer: second law of thermodynamics- A. No heat enters or leaves the system
- B. The temperature remains constant
- C. All work is mechanical
- D. Energy is conserved
Explanation: The first law of thermodynamics states that energy can neither be created nor destroyed, it is converted from one form to another…
Correct answer: Energy is conserved- A. Work done
- B. Exchange of heat
- C. Change in temperature
- D. Change in internal energy
Explanation: An adiabatic process is defined as a process in which no heat transfer takes place.
Correct answer: Exchange of heat- A. The work done by the gas
- B. The work done on the gas.
- C. Change in the internal energy of the gas
- D. Zero, since the process is isothermal
Explanation: During an isothermal process, temperature and internal energy remain unchanged.
Correct answer: The work done by the gas297. A heat engine:
- A. Converts heat input to an equivalent amount of work
- B. Converts work to an equivalent amount of heat
- C. Takes heat in, does work, and loses energy as heat
- D. Uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir
Explanation: A heat engine is a device that operates on the principle of converting heat energy into mechanical work, often by using a working…
Correct answer: Converts heat input to an equivalent amount of work