Answer to Question #89294 in Molecular Physics | Thermodynamics for Shivam Nishad

Question

What are the principles of working of the following temperature measuring devices ?
(a) Bimetallic ship
(b) Thermocouple
(c) Platinum resistance thermometer
(d) Mercury thermometer

Answer 1

a) Bimetallic strip: is a contraction consisting of two plates of different metal. Its principle of operation is based on a different coefficient of linear expansion of the metal. Thus, at one temperature, one plate expands more than the other and the whole structure bends

b)Thermocouple: is a temperature measuring instrument consisting of two early metals. Its principle of operation is based on the Seebeck effect - the occurrence of contact potential difference, if the conductors are located at different temperatures. Placing the junction of metals with non-zero coefficients of thermo-EMF in an environment with a temperature T1, we get the voltage between the opposite contacts located at a different temperature T2, which will be proportional to the temperature difference T1 and T2.

c) Platinum resistance thermometer: is a metal resistance thermometer. It is a resistor made of metal wire or metal film on a dielectric substrate. Its principle of operation is based on the dependence of the resistance of metals on temperature. Platinum thermometer uses platinum.

d)Mercury thermometer: Thermometer consisting of a sealed tube filled with mercury. Its principle of operation is based on the volume expansion of metals with increasing temperature.