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Seebeck Effect |
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Consider two wirers of different metals (say copper and iron)
joined at their ends to form two junctions A and B as shown
in Fig. Such an arrangement is called a thermocouple. If one
junction is kept hot and other cold, it is observed that the
galvanometer shows deflection. This means the e.m.f. is generated
in the circuit. The e.m.f. thus produced is called thermo
e.m.f. and the resulting current is known as thermoelectric
current .The above effect is known as Seebeck Effect and may
be stated as under.
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The phenomenon of e.m.f. in a thermocouple when its two junction
are at different temperature is known as Seebeck Effect. |
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The following point may be noted.
(I) The magnitude and direction of thermo e.m.f. depends
upon the nature of the materials forming the thermocouple and
temperature different between the two junction.
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(II) Usually, thermo e.m.f.
is very small. For Cu-Fe thermocouple, thermo e.m.f. is found
to be about 7µV for every 1oC temperature
difference between the junction; for Sb-Bi thermocouple, it
is 100µV per oC
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(III) The Seebeck effect is
reversible i.e. if hot and cold junction are interchanged,
the direction of thermo e.m.f. is reversed.
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