1. Thermoelectric & Thermionic conversions
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2. By Electromagnetic force 전자기력 (Energy)
Current 전류
Flow of electrons
When electrons flow?
Potential difference [VOLTAGE (+ & -)] path is provided 
By Electromagnetic force 전자기력 (Energy)

3. Basics of thermoelectric conversion Korean definition available at
Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Korean definition available at

4. (Thomas Johann Seebeck, 1821)
Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Solid device
Thermal energy
Electrical energy
By Seebeck effect
(Thomas Johann Seebeck, 1821)

5. Temperature difference produce voltage
Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Circuit made from two dissimilar (different-다른) metals
When junctions maintained at different temperature
Temperature difference produce voltage
How to know the circuit?
By deflection (change the position) 처짐 of compass magnet.
Magnitude of deflection
Proportional (ratio-비율) to temperature different & type of conducting material
Not depends on temperature distribution along the conductor

6. Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Two dissimilar materials joined to form a loop
Two junctions maintained at different temperatures
EMF set up around the loop.
Magnitude of current depends on conduction materials (Metal A and B)
What is loop?
A shape produced by a curve that bends around and crosses itself.
Temperatures measured by thermocouples
heat
Seebeck effect – The principle of thermocouple

7. Seebeck effect Thermocouple 열전대 a sensor used to measure temperature
Used in thermocouple 열전대 & spacecraft 우주선
Thermocouple
Induced emf (electromotive force) is generated together with flow of current
Temperature difference of two metals at two ends in closed circuit
Continues current generation until temperature difference maintained between two ends
High thermal efficiency achieved by semiconductors as they withstand at higher temperature.
Any wastage source of heat [steam, gas, chemical fuel, solar energy & heat from nuclear reactor] used for heating

8. The magnitude of EMF (E-Energy) E = αs ΔT
αs = Seebeck coefficient
ΔT = Temperature difference between hot & cold junction

9. Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Reversible effect of Seebeck effect
When electric current flows across isothermal (constant temperature) junction of two dissimilar (different) materials, either generation or absorption of heat at the junction.
Heat generated by current flows in one direction
Heat absorbed by reversed current flow.

10. Peltier effect (Peltier, 1834)
When current passed between two dissimilar metals
Reverse 반대말 process of Seebek effect
Convert electrical energy into temperature difference of two ends
Lenz, 1938
Heat absorption or generation at junctions depends on direction of current flow
This effect applied to portable electric food coolers/warmers of small size.

11. Peltier’s coefficient α1-2 is
Heat produced or absorbed at junction/unit current flow/unit time
αp1-2 = αp1-αp2 = QP/I
QP = αp1-2I
I = Peltier heat per unit time

12. Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Thomson effect (Thomson, 1851)
Heating or cooling of homogeneous conductor resulting from the flow of electrical current in the presence of temperature gradient (temperature reduction)

13. Positive Thomson effect
Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
The absorption or evolution of heat energy, if a current is allowed to flow in a conductor having it's different parts at different temperatures is known as Thomson Effect
Heated in middle point C
Current flow from A to B
Copper bar AB
When no current flow, point M & N equidistant from C are at the same temperature
When current passed A to B
Temperature: N > M
Similarly, Temperature B > A
Sb, Ag, Zn, Cd   current passed from B to A, M will show higher temperature compared to N
From A to C heat is absorbed and from C to B heat is evolved
Positive Thomson effect

15. Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Iron bar AB heated in middle point C & current flowing from A to B.
When no current is flowing, point M & N equidistant from C are at the same temperature.
Similarly, A will show higher temperature as compared to B.
When current is passed from A to B, M shows higher temperature compared to N.
It means from A to C heat is evolved and from C to B heat is absorbed. This is known as Negative Thomson effect
Similar effect is observed in the case of Pt, Bi, Co, Ni, Hg.

16. Therefore, in the case of lead, Thomson effect is nil.
Heat it at the middle point C
Current is flowing from A to B or from B to A.
Lead (Pb)
M & N equidistant from C same temperature
Therefore, in the case of lead, Thomson effect is nil.

17. Thomson coefficient ()
dQ1/dx =
dT/dx
Where,
dQ1/dx – Heat interchange/unit time/unit length of conductor
dT/dx – Temperature gradient
So, Thomson heat per unit time
dQ dT
----- =  I -----
dx dx

18. Types of thermoelectric effects
Seebeck effect
Peltier effect
Thomson effect
Joule effect
Joule Effect
Heat energy found when electric current flows through a resistance 저항 전기.
In a closed electric circuit if the current flows through a resistor R, the heat generated (Q) by the resistor is equal to I2R
Q = I2R
I – Peltier heat per unit time
Electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. 

19. Construction of thermoelectric generator
By using special semiconductor materials for optimization of seebeck effect.
Components
Thermocouple
p-type & n-type material connected electrically in series & thermally in parallel
Burner box
Exhaust

20. Thermionic conversion system
Emission of electrons from heated metals & some oxides surfaces is known as thermionic emission
Small current production
Required high temperature (1000 oC)
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21. Consists of
Metal electrodes – cathode (tungsten) & anode cesium coated tungsten
Sealed container – ionized gas or cesium vapour
Heat the cathode (1000 oC) emitted electrons move to anode
Production of number of electrons depends on temperature
Voltage developed between the electrodes
Current flow in external circuit
Heat converted electrical energy
Accumulation of electrons in anode – Space charge
Current density J = AT2 e-b/T A/m2
b = e/K
Where, T – temperature of the surface K
A – constant
e – natural log base
b – oK constant
K - Boltzmann constant