The document discusses various topics related to low temperature physics and thermoelectricity: 1. It lists the group members and their roll numbers working on the project. 2. It discusses low temperature physics, the Joule-Thomson effect, thermoelectricity, thermocouples, the Seebeck effect, and the Peltier effect. 3. Different group members provide explanations and examples for various topics like thermoelectric materials and applications, how thermocouples work, and the scientific principles behind the Seebeck and Peltier effects.

2. Group member
Name Roll no
Maryam 15261509-022
Sundas 15261509-009
Iqra 15261509-018
Saira 15261509-005
Samra 15261509-035

3. Content:
• Low Temperature physics
•Thermo Electricity
•Thermo couple
• Thermo seabeck’s effect
• Peltier’s effect

4. 1. Low
Temperature
Physics

5. Temperature:
A measure of the warmth or
coldness of an object or substance
with reference to some standard
value. The temperature of two
systems is the same when the
systems are in thermal equilibrium.
www.dictionary.com/browse/temperature

6. Thermodynamics by Prof.M.H.Musaddiq
low temperature:
In every day life, temperature
below or around 0 °C are termed
as low temperatures. The branch of
physics which deals with production
of low temperature is called
cryogenics or low temperature
physics.

7. www.comsol.com/multiphysics/joule-thomson-effect
Joule thomsan effect:
For several years, James Prescott Joule and
William Thomson – both British physicists –
worked in collaboration, conducting experiments
designed to analyze and advance
thermodynamics. In 1852, the researchers made
a particularly notable discovery. They found that
a temperature change can occur in a gas as a
result of a sudden pressure change over a valve.
Known as the Joule-Thomson effect (or
sometimes the Thomson-Joule effect

8. James Prescott Joule

9. William Thomson

10. Samra
2.Thermo Electricity
by

11. CONTENTS:
1: Introduction
2: Why Thermoelectricity?
3: Principle
4: Working and Construction
5: Material of choice for TEG
6: Advantages and Disadvantages
7: Applications
8: Conclusion

12. INTRODUCTION:
Thermoelectric power generation using waste
heat energy as an alternative green
technology..

13. Why thermoelectricity?
• Increasing energy demand..
• Increasing pollution..
• Increasing IC heat..
• Green energy production by thermoelectricity.
• Automobile waste heat thermoelectric power
generation.
• On chip thermoelectric cooling.

14. How does thermoelectricity work?
In 1821, Thomas Johann SeeBeck discovered
that a thermal gradient formed between two
dissimilar conductors can produce electricity.
At the heart of the thermoelectric effect is the
fact that a temperature gradient in a
conducting material results in heat flow; this
results in the diffusion of charge carriers.

15. WORKING:

16. Material of choice for
thermoelectricity:
 TE Parameters Materials..
 Semiconductors most suitable TE material.
Allow separate control of G (electrons) and κ
(phonons)

17. Choice of material:

18. advantages and disadvantages:
ADVANTAGES
Environmentally friendly
Recycles wasted heat energy
Reliable source of energy
Lowers production cost

19. DISADVANTAGES:
• TE material is expensive.
• Structural failure of TE element at high
temperatures.
• Electrical resistivity increases.

20. CONCLUSION:
Thus, by using Teg, the waste heat can be used
to generate electricity.
Simulations and experiments has been
conducted and more efficient systems can be
developed in future with Nanocrystalline
approach.

21. Iqra
3.Thermo couple

22. Thermocouple:-
Thermocouple is a combination of two words:
Thermo:
relating to heat.
Couple:
a pair of forces.

23. What is a Thermocouple?
A thermocouple is a temperature measuring device
consisting of two dissimilar wires forming electrical
junctions at different temperatures. A thermocouple
produces a temperature-dependent voltage as a result of
the thermoelectric effect, and this voltage can be
interpreted to measure temperature. Thermocouples are
a widely used type of temperature sensor.
Zemansky-Heat And Thermodynamics

24. Thermocouple wires:-

25. How does a thermocouple work?
When two wires composed of dissimilar metals are
welded at both ends , creating a junction and the
junction is heated. This junction is where the
temperature is measured. When the junction
experiences a change in temperature, a voltage is
created. Which means that when the junction of the
two metals is heated, or cooled, a voltage is produced.
http://www.thermocoupleinfo.com/

27. Thermocouple types:-
Thermocouples are available in different
combinations of metals or calibrations:
“Base Metal” “Noble Metal”
Type J Type R
Type K Type S
Type T Type B
Type E Type C
http://www.thermocoupleinfo.com/

28. Applications:-
• Steel industry.
• Temperature sensor for measurement.
• Control and convert temperature in electricity.
• In stoves & tosters.
• Used in researches.
• Used in offices.
• Used in homes.
• Temperature measurement for furances.
https://www.slideshare.net/ShyamakantSharan/ppt-thermocouple

29. Working Principle:-
The working principle of the
thermocouple is based on two effects
discovered by:
• Seebeck effect
• Peltier effect
They are as follows:
https://www.slideshare.net/keshavakrishnan34/thermocouple-52341426

30. Sundas
4.Seebeck effect
by

31. History
In 1821, Seebeck found that:
A current flows in a circuit consisting
of two dissimilar metals, when one
junction is heated, while other
junction is kept cold.

32. Seebeck effect
The existence of a thermal emf €AB in the
circuit is known as the Seebeck effect. In
figure, a thermocouple consisting of two
different conductors A and B has its junctions
in contact with different heat reservoirs. We
call the warmer junction at T the test
junction, and the other at temperature TR
the reference junction.
Zemansky-HeatAndThermodynamics

33. Zemansky-HeatAndThermodynamics

34. Conti …
When the temperature of the reference
junction is kept constant, the thermal
emf is found to be a function of the
temperature T of the test junction. This
fact enables the thermocouple to be used
as a thermometer.
Zemansky-HeatAndThermodynamics

35. Conti …
The Seebeck effect arises from the fact
that the density of charge carries
(electrons in a metal) differs from one
conductor to another and depends on the
temperature. When two different
conductors are connected to form two
junctions and two junctions are
maintained at different temperatures.
Zemansky-HeatAndThermodynamics

36. Conti …
For a given TR, €AB is a function
of T. If TR is changed to another
constant value, the relation
between €AB and T is the same
expect for an additive constant.
Zemansky-HeatAndThermodynamics

37. Conti …
It follows therefore that the value of
d€AB/dT is independent of TR and
depends only the nature of A and B
and upon T. The derivative d€AB/dt , at
any value of TR , is known as the
thermoelectric power of the
thermocouple.
Zemansky-HeatAndThermodynamics

38. Peltier effect
• In 1834, a French watchmaker and part time
physicist, Jean Peltier found that an electrical
current would produce a temperature gradient at
the junction of two dissimilar metals
•
• when the current direction was
r reversed, the cold junction
w would get hot while the hot
junction w would get cold.

39. Cause of peltier effect
• When a current flows
across the junction of
two metals, it gives rise
to an absorption or
liberation of heat,
depending on the
direction of the
current. i.e. Applying a
current (e- carriers)
transports heat from the
warmer junction to the
cooler junction.

40. Example
• As an example of the Peltier effect, consider the circuit shown here.
Under these conditions, it is observed, as indicated in the diagram, that
the right-hand junction is heated. It shows, in other words, that electrical
energy is being transformed into heat energy. Meanwhile, heat energy is
transformed into electrical energy at the left junction, thereby causing it
to be cooled. When the current is reversed, heat is absorbed at the right
junction and produced at the left one.

41. Conti.
– The rate of evolution of or absorption of heat is
proportional to the current &thus the peltier effect is
reversible.
• If direction of current is changed then the peltier effect
is also reversed.
• The energy absorbed or evolved at one of the junctions
of the two dissimilar metals when one ampere of
current flows for one second is called Peltier coefficient
,denoted by ∏

42. Experimental demonstration of peltier
effect
• In this experiment, two rods of bismuth and antimony
are joined as shown.
• A differential air
thermometer is
placed with its two
bulbs at
junctions A and B.

43. Conti..
• When no current flows through the thermocouple , the
junctions A & B are at same temperature.
• When large current is passed through the thermocouple ,
then there will be:
– Evolution of heat at junction A.
– Absorption of heat at junction B.
– Hg pellet moves to one direction
• If direction of current is changed the pellet moves in the
opp. Direction indicating that now A has become cold
and B has become hot.