Application of Thermo Electric Effect
Category : JEE Main & Advanced
(1) To measure temperature : A thermocouple is used to measure very high \[({{20000}^{o}}C)\] as well as very low \[(-{{200}^{o}}C)\]temperature in industries and laboratories. The thermocouple used to measure very high temperature is called pyrometer.
(2) To detect heat radiation : A thermopile is a sensitive instrument used for detection of heat radiation and measurement of their intensity. It is based upon Seebeck effect.
A thermoppile consists of a number of thermocouples of Sb-Bi, all connected in series.
Heating effect and Thermo-electric effects
| S. No. | Joule's effect | Peltier's effect | Seebeck effect | Thomson's effect |
| 1. | Heat produced is directly proportional to the square of the current passing through a conductor. | Heat produced or absorbed at a junction is proportional to the current through the junction. | Here temperature difference of junction is used to produce thermo e.m.f. and vice versa. | Thomson's heat is proportional to the current passing through the conductor. |
| 2. | This effect is produced due to collision of free electrons with positive ions of the current carrying conductor. | This effect is produced when current is passed through junction of suitable materials. | This effect produced when junctions of a themocouple are kept at different temperatures. | This effect is produced when parts of same conductor are kept at different temperature. |
| 3. | It is not a reversible effect. | It is a reversible effect | It is a reversible effect | It is a reversible effect |
| 4. | Heat produced depends upon resistance (and thus temperature also) of the conductor. | Heat exchange depends upon nature of conductors and temperature of the junctions. | This effect depends upon nature of materials used to form junctions and temperature of junctions. | This effect depends upon nature of conductor and temperature difference of different parts of the conductor. |
| 5. | It is basically a heating effect | It can be heating as well as cooling effect. | Different junctions are at different temperature. | It is heating as well as cooling effect. |
This instrument is so sensitive that it can detect heat radiations from a match stick lighted at a distance of 50 metres from the thermopile.
(3) Thermoelectric refrigerator : The working of thermo-electric refrigerator is based on Peltier effect.
(4) Thermoelectric generator : Thermocouple can be used to generate electric power using Seebeck effect in remote areas.
(5) Thero-couple meter : The current to be measured passes through a resistance where heat is generated in the amount of i2R joule/sec. The hot junction of the thermocouple is in contact with this resistance, and resulting thermoelectic current gives deflection in the galvanometer G.
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