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Question
The constants a and b for the pair silver-lead are 2.50 μV°C−1 and 0.012μV°C−2, respectively. For a silver-lead thermocouple with colder junction at 0°C, ______________ .
(a) there will be no neutral temperature
(b) there will be no inversion temperature
(c) there will not be any thermo-emf even if the junctions are kept at different temperatures
(d) there will be no current in the thermocouple even if the junctions are kept at different temperatures
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Solution
(a) there will be no neutral temperature
(b) there will be no inversion temperature
The temperature of the hot junction at which the thermo-emf in the thermocouple becomes maximum is called neutral temperature for that thermocouple. The signs of the constants a and b are same. Therefore from the relation, \[\theta_n = - \frac{a}{b},\] the neutral temperature will be less than the temperature of the cold junction of thermocouple.
Hence, there will be no neutral or inversion temperature, as the temperature of the hot junction cannot be less than the temperature of the cold junction.
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