The Law of Thermodynamics:
Hello , today we are going to learn law of thermodynamics,
Why it is important in daily life.
Law of thermodynamics tells us why some energy or heat flows in certain direction
A thermodynamic system is a body of matter and / or radiation, confined in space by walls, with defined permeabilities, which separate it from its environment. A widely used distinction is that of isolated, closed and open thermodynamic systems.
There are 4 laws of thermodynamics
Lets see one by one
Zeroth law of thermodynamics Statement:
This law is just an observation. It states that If two systems are both in thermal equilibrium with a third system then they are in thermal equilibrium with each other.
 |
| A |
|
| B |
|
| C |
Suppose if we put glass A near to B, then both glass will achieve thermal equilibrium with each other.
and then if we put both glass A and B near to C then all the glasses will get thermal equilibrium with each other.
Application of zeroth law of thermodynamics:
When we use the thermometer to check our body temperature ,then our body and thermometer get in thermal equilibrium with each other.
First Law of Thermodynamics:
This law states that energy cannot be created or destroyed. It can be transferred from one location to another and converted to and from other forms of energy. Mathematically it states that,
ΔU = Q – W,
Where ΔU is change in internal energy of system, Q is heat added to the system and w is work done by the system
Let us consider water as ΔU , when we add a heat Q to the water, then the internal energy of water is changed.
The state of water changes from liquid to water vapour,if we restrict the flow of water vapour by placing plate on water glass. Then water vapour exert pressure on plate
means this pressure will try to remove the plate. This is work done to the plate
Application of First Law of Thermodynamics
Heat engine
Refrigerators,
air conditioners
heat pumps, etc
Second Law of Thermodynamics:
This law mainly focuses on entropy
The change in entropy Δ S is equal to the heat transfer delta Q divided by the temperature T.
Δ S = ΔQ/T
But what is Entropy ?
It is a measure of disorder of a system. We can also say Entropy as inside transformation
The second law of thermodynamics also states that the total entropy of a system either increases or remains constant; it never decreases. Entropy is zero in a reversible process; it increases in an irreversible process.
Confuses?
If we put Hot object into a cold object , we know heat is transferred from the hot object into the cold object. And after some time they will achieve thermal equilibrium .
If you separate these two objects, these two objects do not return to their original temperature.
In this example entropy of both systems increases, meaning the hotter object will never be a hotter, unless we apply some external force.
Third Law of Thermodynamics:
The entropy of a system approaches a constant value as its temperature reaches absolute zero.
Let's take a simple example to understand.
Entropy of a system at absolute zero temperature is expressed as
S – S0 = KB lnW
S is the entropy of a system,
S0 is the initial entropy of a system,
KB is the Boltzmann constant.
W total number of microstates
At absolute zero temperature , there is only one microstate, know as ground state.
So W=1,
So above equation becomes
S-S0= KB ln1
S-S0= 0
So the entropy of a system approaches to zero at absolute zero temperature.
But practically it requires more number steps to reach absolute zero (0 k). So entropy of a system will approach zero. Not exactly zero.
Even at 0 K; there will be some thermal motion within the system, which leads to disorder. And entropy
Third law of thermodynamics helps in the measurement of the absolute entropy of a substance at any temperature ‘T’.
Hope you like this article, please comment below.
Please check following source for more details
Sources:
https://www.grc.nasa.gov/WWW/K-12/airplane/thermo2.html
https://www.livescience.com/50942-third-law-thermodynamics.html
https://en.wikipedia.org/wiki/Third_law_of_thermodynamics
Comments
Post a Comment