1. (a b) Isothermal expansion at thermodynamic temperature T1 with heat q1 taken in. Heat energy is absorbed from a high-temperature source at constant temperature. The volume increases while the pressure drops somewhat.The net result is that of the heat abstracted from the hot source, some, represented by the area abcd, is converted into mechanical (or electrical) work, the rest being rejected to the sink. According to the Carnot principle, the efficiency of any reversible heat engine depends only on the temperature range through which it works, rather than the properties of the working substances.
It's important to recognize that what Carnot describes is an idealized heat engine. It proved useful for showing how steam engines (which were then being developed) could operate most efficiently. It was also a forerunner of the internal combustion engine.
Related entries• Brayton cycle
• Rankine cycle
Related category• HEAT AND THERMODYNAMICS
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