What is thermodynamics
Thermodynamics
Therm=heat and Dynamics= motion (caused due to force)
The main aim
of Thermodynamics is to convert non organised form of heat to organized form of
work.
DEFINITION
Thermodynamics
is a branch of science deals with heat and work interactions of the system and
its effects on the properties of the system.
This is
based on some basics laws like law of conservation of energy, law of
conservation of mass, etc
To
understand the definition of thermodynamics you have to know what is heat and
work.
HEAT:
It is
a transient form of energy which transfer due to negative temperature gradient
i.e from high temperature to low temperature.
𝑄 ∝ 𝑀
𝑄 ∝ ∆𝑇 𝑄 ∝ 𝑀∆𝑇
𝑄 = 𝑀𝐶∆𝑇
WHERE,
Q=HEAT transfer in KJ
∆𝑇=Temperature difference
M=mass
C=specific heat
It is defined as the amount of heat required to
increase the temperature of one kg of substance through 1℃.
If m=1, ∆𝑇 = 1℃
C=Q
Work:
In layman language,
work is task to be undertaken.
But in thermodynamics,
work is said to be done by system if sole effect is external to the system that
can be reduce to lift the weight.
Note:
1.Work is boundary
phenomena it has only significance when it crosses the boundary of the system.
2.Work transfer is the transfer
of energy across the boundary other than due to temperature difference.
HIGH GRADE ENERGY AND LOW GRADE ENERGY:
Work is considered as high-grade
energy and heat is considered as low-grade energy. Because work is energy uses
motion of organized form of atoms in surrounding that’s convert completely into
heat but reverse is not possible.
How to study thermodynamics:
There are two
approaches to study thermodynamics as follows;
1.Microscopic view (Statistical approach):
In this our attention
is focus on each and every molecules of the system and to know the overall behaviour,
we will sum of the behaviour of all by statistical means.
It’s useful for low densities
(low pressure gases).
Individual behaviour of
molecules is concern.
2.Macroscopic view (Classical approach):
In this, our attention
is focus on certain quantity of matter without going the event occurring at
molecular level, it also known as classical thermodynamics.
When to use Macroscopic view point?
Concept of Continuum: It
gives criteria to apply the macroscopic view point. Its gives minimum volume which
we have consider so that averaging is meaningful and matter can be treated as continuous.
For solid and liquid
its always hold good but for gases it’s not always so true
To check whether
concept of continuum valid or not Knudsen number is used which is the ratio of
mean free path to characteristics dimension.
If Kn<0.01 then, concept of continuum
valid and we can use macroscopic view point.
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