A heat engine:
Correct answer: A. Converts heat input to an equivalent amount of work
- 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 substance like steam or gas. The engine absorbs heat from a high-temperature reservoir, does work, and expels some heat to a low-temperature reservoir, making it an essential part of many machines, such as steam engines, petrol engines, and diesel engines.Option A is correct because it accurately describes the core function of a heat engine. Option B is incorrect because it describes a heat pump or refrigerator's function, where work is used to move heat against its gradient. Option C, while partially correct, does not highlight the conversion of heat energy to work as the primary purpose. Option D correctly describes a heat pump, not a heat engine.
This question appeared on the ETEA MDCAT 2016 paper, which you can sit online with every answer explained.
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About First Law of Thermodynamics
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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