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Question
State the various statements of the second law of thermodynamics.
Solution
- Entropy statement: Whenever a spontaneous process takes place, it is accompanied by an increase in the total entropy of the universe”.
- Kelvin-Planck statement: It is impossible to take heat from a hotter reservoir and convert it completely into work by a cyclic process without transferring a part of heat to a cooler reservoir.
- Efficiency statement: Even an ideal, frictionless engine cannot convert 100% of its input heat into work.
Efficiency = `("T"_1 - "T"_2)/"T"_1`
% Efficiency = `[("T"_1 - "T"_2)/"T"_1] xx 100`
% Efficiency = `["Output"/"Input"] xx 100`
% Efficiency < 100% - Clausius statement: Heat flows spontaneously from hot objects to cold objects and to get it to flow in the opposite direction, we have to spend some work.
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