Thermodynamics EquationsThermodynamics Equations
Thermodynamics is expressed by a mathematical framework of thermodynamic equations
which relate various thermodynamic quantities and physical properties measured in a
laboratory or production process. T
hermodynamics is based on a fundamental set of postulates, that became the laws of
One of the fundamental thermodynamic equations is the description of thermodynamic work in
analogy to mechanical work, or weight lifted through an elevation against gravity, as defined in
1824 by French physicist Sadi Carnot.
Carnot used the phrase motive power for work. In the footnotes to his famous On the Motive
Power of Fire, he states: "We use here the expression motive power to express the useful
effect that a motor is capable of producing.
This effect can always be likened to the elevation of a weight to a certain height. It has, as we
know, as a measure, the product of the weight multiplied by the height to which it is raised."
With the inclusion of a unit of time in Carnot's definition, one arrives at the modern definition
for power:Know More About :- First Ionization Energy Math.Tutorvista.comPage No. :- 1/4
A thermodynamic system is in equilibrium when it is no longer changing in time. This may
happen in a very short time, or it may happen with glacial slowness.
A thermodynamic system may be composed of many subsystems which may or may not be
"insulated" from each other with respect to the various extensive quantities.
If we have a thermodynamic system in equilibrium in which we relax some of its constraints, it
wil move to a new equilibrium state.
The thermodynamic parameters may now be thought of as variables and the state may be
thought of as a particular point in a space of thermodynamic parameters. The change in the
state of the system can be seen as a path in this state space.
This change is cal ed a thermodynamic process. Thermodynamic equations are now used to
express the relationships between the state parameters at these different equilibrium state.Thermodynamics Examples
The evaporation of sweat from your body is an example of thermal equilibrium in action.Solution A :-System :-
The sweatSurroundings :-
Your body + the rest of the universe
q > 0 so, Heat flows into the system (sweat) from you in order to raise the kinetic energy of the
sweat molecules enough to al ow them to go from the liquid phase to the gas phase.Solution BSystem :-
The sweat + the rest of the universeLearn More :- Ionization Energy Trend Math.Tutorvista.comPage No. :- 2/4
Q < 0 :-
Heat flows out of the system (you) into the sweat.
Since heat leaves your body this cools you down. This is the reason for our sweating.Example of thermal equilibrium :-
Let us consider two beakers full of water. Then for one
beaker, the temperature of water is above the normal room temperature, and for the other
beaker it is below the normal room temperature.
They are left on the table for sometime such that they both are not in contact with each other.
If we check the beakers after some time, equilibrium for both the beakers is reached. As
observed both the beakers of water are at the same temperature.
The two beakers actual y come in thermal equilibrium with the surroundings. Hence they are
in thermal equilibrium with each other also and they are at the same temperature.Practice ProblemsQuestion 1:
Suppose a man standing on top of a tower, 200m tall. He is holding a small,
heavy ball that weighs 5kg. What would be the velocity of the bal be when it hits the ground
assuming it was dropped on the ground with zero initial velocity? What would be the velocity
of the bal be when it hits the ground assuming it was dropped on the ground with 20m/s?Question 2:
Water is flowing at the rate of 2 litres per minute from a tap and a geyser is
heating it such that the temperature rises from 23 to 77 degree centigrade. If the geyser is
supplied and aided with a burner than find the rate of combustion of the fuel given the heat of
combustion is 2 x 100000 J/g.Question 3:
Why does the air pressure of the tire rises during driving? Question 4:
Why the coolant used in nuclear plants should have more specific heat? Math.Tutorvista.comPage No. :- 4/4