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trungdien
From what I have heard, entropy is the amount of energy that is unavailable to do work. What exactly does it mean by "unavailable energy", and can someone give some examples of energy being unavailable to do work in real life?
Understanding Entropy: Examples of Unavailable Energy in Everyday Life
- Thread starter trungdien
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In summary, entropy is a measure of the energy that is not available to perform work. This can be seen in the example of water at room temperature containing energy, but not being able to heat up a mug of coffee already at a higher temperature without an external source of energy. The concept of available and unavailable energy is further explored in the Wikipedia article on exergy, which provides both theoretical explanations and real-life examples.
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CWatters
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Water at room temperature (20C) contains energy (because it's not at absolute zero) but that energy can't be used to heat up a mug of coffee already at 30C (You could do it using a heat pump but that needs an external source of energy).
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anorlunda
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You can talk about the unavailable or the available fractions of total energy.
See the Wikipedia article https://en.wikipedia.org/wiki/Exergy
It explains both theory and practical examples.
1. What is entropy?
Entropy is a measure of the disorder or randomness in a system. It is a thermodynamic property that describes the amount of unavailable energy in a system.
2. How does entropy relate to unavailable energy?
The higher the entropy of a system, the more unavailable energy it contains. This means that as a system becomes more disordered, the energy within it becomes less useful for doing work.
3. Can you give an example of entropy in everyday life?
One example of entropy in everyday life is the melting of ice cubes. As the ice melts, it becomes more disordered and its entropy increases. The unavailable energy in the ice cubes (in the form of potential energy) is converted into kinetic energy as the molecules move more freely, making it difficult to re-freeze the melted ice.
4. How does the concept of entropy apply to the universe?
The second law of thermodynamics states that the total entropy of the universe is always increasing. This means that as energy is transferred or transformed, some of it becomes unavailable and contributes to the overall increase in entropy of the universe.
5. Can entropy be reversed or reduced?
Entropy can only be reduced or reversed in localized systems with an input of external energy. However, the overall entropy of the universe will continue to increase. This is why it is often said that entropy is a one-way street; once energy becomes unavailable, it cannot be restored to its original state.
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