Basic doubt in thermodynamics 2nd law

In summary: For something to have low entropy, it needs to be in a state of order (which is usually not the case for cells). For something to have high entropy, it needs to be in a state of disorder (which is usually the case for cells).
  • #1
aditya23456
114
0
I ve read that according to 2nd law,in a closed system where there's no inflow and outflow of energy,the potential energy of such system continuously decreases...
So where does/ what is this energy converted to.?
 
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  • #2
aditya23456 said:
I ve read that according to 2nd law,in a closed system where there's no inflow and outflow of energy,the potential energy of such system continuously decreases...
So where does/ what is this energy converted to.?

I think you might have misquoted and/or misunderstood the 2nd law! The Second Law of Thermodynamics has been written in many different forms, but they all say something like this:

The entropy of a macrostate of a closed system never decreases.

I don't know of any law that says the potential energy of a closed system must decrease. For example, consider an ideal box of ideal gas molecules in thermal equilibrium at constant temperature. Thermodynamics says the total potential energy of that system is constant.
 
  • #3
according to 2nd law,in a closed system where there's no inflow and outflow of energy,

What do you mean by this?

Are you trying to describe a closed system which means there is no inflow or outflow of mass? Energy may, however be exchanged.

Or are you adding the extra restriction to make the system isolated?

Either way if your intention is to restrict energy exchange so that the total energy of the system is constant, are you trying to describe the idea that lead to the 'heat death of the universe' where potential energy is converted to kinetic energy at maximum entropy?
 
  • #4
It has been stated so--
"In all energy exchanges if no energy energy enters or leaves the system,the potential energy of state is always less than that of initial state.This is commonly referred as entropy"
Is this right.?
 
  • #5
What do you mean by this?
"In all energy exchanges if no energy energy enters or leaves the system [...]
What is exchanged, if nothing is exchanged?

An isolated system can increase its potential energy. Think of a fast-moving ball, rolling up a hill (with gravity) and coming to a rest there. Earth+Ball increased the potential energy, while the system "earth+ball" could be isolated from the rest of the universe in this hypothetical experiment.
 
  • #6
aditya23456 said:
It has been stated so--
"In all energy exchanges if no energy energy enters or leaves the system,the potential energy of state is always less than that of initial state.This is commonly referred as entropy"
Is this right.?

Whoever said this has absolutely no idea what he/she is talking about.

  1. The quote defines "energy exchange" as an interaction of an isolated system with itself in a way that does not exchange energy. That's not a useful definition.
  2. As written, the quote says the potential energy of a system's state is always less than that of its initial state. That means the state's initial potential energy is less than itself, which means -1 = 0.
  3. Let's assume the quote meant to say "the potential energy of [a final] state is always less than that of [an] initial state." That is false. (The ball rolling up a hill is, IMO, a clear and simple counterexample.)
  4. Nothing in the quote has any relation to entropy.

Here are some common definitions of entropy:

Old thermodynamic entropy (Boltzmann)

New thermodynamic entropy (Gibbs)

Information entropy (Shannon)

Quantum entropy (von Neumann)
 
  • #7
Umm..but just google what I ve quoted,u'll find many links where the 2nd law of thermodynamics is explained so..That's the reason I felt some inconsistancy with general accepted law...so this manifests that all the links which stated so are wrong.! Isn't it..?
 
  • #8
one the link gives following example--
A watchspring-driven
watch will run until the potential energy
in the spring is converted, and not
again until energy is reapplied to the
spring to rewind it. A car that has run
out of gas will not run again until you walk 10 miles to a gas station and refuel
the car. Once the potential energy
locked in carbohydrates is converted
into kinetic energy (energy in use or
motion), the organism will get no more
until energy is input again. In the process of energy transfer, some
energy will dissipate as heat. Entropy is
a measure of disorder: cells are NOT
disordered and so have low entropy.
The flow of energy maintains order and
life. Entropy wins when organisms cease to take in energy and die.
THANKS FOR INFO THOUGH,i'll read them out now..
 
  • #9
These are just examples where potential or chemical energy is converted into heat, which is usually not reversible in everyday applications.
The important part here is the heat (which usually has high entropy per energy, compared to other energy forms).
 

Related to Basic doubt in thermodynamics 2nd law

1. What is the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This means that the disorder or randomness of a system will always tend to increase, and that it is impossible to completely convert heat energy into work without any loss.

2. How does the second law of thermodynamics relate to energy efficiency?

The second law of thermodynamics is closely related to energy efficiency. It states that no process can be 100% efficient, meaning that there will always be some energy lost in the form of heat. This is why it is important to design systems and processes that are as efficient as possible, in order to minimize energy waste.

3. What is the difference between the first and second law of thermodynamics?

The first law of thermodynamics is known as the law of conservation of energy, and it states that energy cannot be created or destroyed, only transferred or converted. The second law, on the other hand, focuses on the direction of energy transfer and the tendency of systems to increase in entropy.

4. Can the second law of thermodynamics be violated?

No, the second law of thermodynamics is a fundamental law of nature and cannot be violated. It has been extensively tested and proven through various experiments and observations. While it is possible to temporarily decrease the entropy of a system, it will always increase over time in accordance with the second law.

5. How does the second law of thermodynamics apply to everyday life?

The second law of thermodynamics has many practical applications in our daily lives. For example, it explains why it is impossible to create a perpetual motion machine, as energy will always be lost in the form of heat. It also helps us understand why energy efficiency is important in everything from household appliances to industrial processes.

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