Question

A platinum resistance thermometer has resistances of 200.0 ohms when placed
in a 0 degrees Celsius ice bath and 253.8 ohms when immersed in a crucible contacting melting potassium. What is the
melting point of potassium? Hint: First determine the resistance of the platinum resistance
thermometer at room temperature, 20 degrees Celsius.

Answer 1

for Pt α =0.00392 (1/℃).

R₁=R₀[1+α(T₁-T₀)]
R₂= R₀[1+α(T₂-T₀)]

R₁/R₂=[1+α(T₁-T₀)]/[1+α(T₂-T₀)]
200/253.8=(1- 0.00392 •20)/[1+ 0.00392• (T₂-20)]
Solving for T₂ gives
T₂=63.2℃