PASCO TD-8550A THERMOELECTRIC CONVERTER - Manual (Page 3)

012-04929A
3 scientific
Description of Seebeck effect
The Thermoelectric Converter uses a series of thermo-
electric cells to convert thermal energy into electrical
energy that will drive the fan. Each cell is a semicon-
ductor device. A simplified diagram of one cell is
shown below.
During the Seebeck effect, the heat entering the cell
raises the energy level of some of the electrons in the
cell. At the higher energy level, the electrons are no
longer bound in the crystal structure of the semicon-
ductor and are free to move. When they do so, they
leave a vacant place, or hole, in the crystal. Lower
energy electrons, though they can’t move freely within
the material, can jump from hole to hole. In this way,
the holes can also migrate through the semiconductor
material.
H
O
T
C
O
L
D
Thermoelectric
Cell
FAN
MOTOR
Thermoelectric Converter Cell (Seebeck effect)
PASCO
scientific
TD-8550A
Thermoelectric
Converter
+ –
A) ∆ T–E
B) E– ∆ T
TO
POWER SUPPLY
(5 VDC, 3 A)
2 min, 8 VDC MAXIMUM
COLD
PELTIER EFFECT
(E ➞ ∆
T)
HOT
SWITCH IS IN
"DOWN" POSITION
Peltier Effect:
During the Peltier effect, a current through the thermo-
electric heat pump of the Converter causes a tempera-
ture difference. Connect a DC power supply capable of
5 Volts and 3 Amps to the red and black terminals on
the Converter. Put the switch on the Converter to the
E
→ ∆
T (down) position . (For this demonstration,
you do not need to immerse the legs of the Converter
in water.) Turn on the power supply. In a few mo-
ments you should be able to feel the temperature
difference of both aluminum legs of the Converter.
➧
NOTE: DO NOT LEAVE THE POWER
SUPPLY ON FOR MORE THAN TWO MIN-
UTES. DO NOT EXCEED 8 VOLTS.
As an optional exercise, begin with the Converter at
room temperature. Measure the temperature of both
legs. Then, while the current is applied to the Con-
verter, use a digital thermometer to monitor the increase
in temperature of the “hot” leg and the decrease in
temperature of the “cold” leg.
Thermal Capacitor:
After demonstrating the Peltier effect, disconnect the
power supply from the Converter. Put the switch to the
∆
T
→
E (up) position. The temperature difference
caused when the current was applied to the thermoelec-
tric heat pump will now cause the Converter to generate
a current to drive the motor.
PASCO
scientific
TD-8550A
Thermoelectric
Converter
+ –
A) ∆ T–E
B) E–
∆ T
"THERMAL CAPACITOR"
(MODIFIED SEEBECK EFFECT)
FAN ROTATES