statistical Mechanics

1. PG & RESEARCH DEPARTMENT OF PHYSICS
Dr. E. SINDHUJA M.Sc., Ph.D.

2. Can anyone say the 100 words in which there are no
ABC?
Warm up
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3. Warm up
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4. Thermodynamics
Thermo – Thermal – Temperature- Heat
Dynamics - Change within a system, Motion of bodies
Thermodynamics is the study of the effect of work, heat and energy on a
system.
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5. Thermodynamics Laws
Zeroth Law
First Law
Second Law
Third Law
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6. Info-bits
Zeroth Law –Thermodynamic Equilibrium and temperature
First Law- Work, Heat and Energy
Second Law- Kelvin-Plank, Clausius
Third Law- Absolute Zero
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7. The zeroth law of thermodynamics states
that if two thermodynamic systems are
each in thermal equilibrium with a third,
then all three are in thermal equilibrium
with each other.
if Object A and Object C is in thermal
equilibrium (it means that both are at the same
temperature or there is no energy transfer
between these two blocks in the form of
heat), and also If Object B and Object C is in
Thermal Equilibrium with each other, then
Object A and Object B will also be in Thermal
Equilibrium with each other.
Zeroth Law of Thermodynamics
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8. Measuring our body temperature using mercury thermometer.
When mercury thermometer is placed on our body, the glass wall of the
thermometer first attains equilibrium with our body due to heat conduction. Then
equilibrium is attained between the glass wall and the mercury.
So if our body and mercury are in thermal equilibrium with the glass wall. Then
our body and mercury are in thermal equilibrium with each other ie.Mercury shows
the exact body temperature.
Contd….
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9. The first law of thermodynamics, also known as Law
of Conservation of Energy, states that energy can
neither be created nor destroyed; energy can only be
transferred or changed from one form to another.
The First Law is also says that the internal energy of a
system has to be equal to the heat absorbed by the
system, plus work done on the system.
First Law of Thermodynamics
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Take your bike engine. We fuel it with
petrol. Petrol contain chemical energy.
When it is burned this chemical energy
converted to mechanical energy.
Another example is our body. When we
feed we get energy and that energy will be
converted to useful work we do.
Contd….

11. Kelvin Plank statement: It is impossible to convert
all heat taken from a body into work without causing
other changes.
The best example of this statement is Human Body.
We eat food . The chemical energy of food is utilized
by body to maintain its temperature and to do work.
When we do some work our body warms up and
rejects heat into the environment. Even if we are not
doing any work our body still rejects a lot of heat to
environment due to metabolism.
Second Law of Thermodynamics
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12. Clausius statement: It is impossible for a
self acting machine, unaided by any
external agency, to transfer heat from cool
body to a hot body
The best example of this statement can be
a hot cup of coffee kept on a table. The
coffee will eventually cool down showing
that heat only flows from high temperature
to low temperature without the aid of any
external agent.
Contd….
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13. The Entropy of a system approaches a constant value as its
temperature approaches absolute zero
An object or substance with high entropy is highly disordered. Entropy in
the universe can only increase. The third law of thermodynamics says
that the entropy of a perfect crystal at absolute zero is exactly equal to
zero. Absolute zero is the temperature at which molecules stop moving
or vibrating at all.
It states that if something becomes 0°K or -273.15°C or -459.67°F then
its atoms stop moving. This temperature is called absolute zero.
Third Law of Thermodynamics
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Laws of thermodynamics in terms of kinetics of atoms or molecules
in a macroscopic object
Studying macroscopic properties of systems in terms of their
microscopic properties.
Statistical Mechanics

16. The Zeroth law : if A=B;A=C; B=C
The First law : Conservation of Energy
The second Law : Kelvin Plank statement ; Clausius statement
The Third Law : Absolute zero temperature is unattainable
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Review Zone

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