university physics
posted by Ella .
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.

for Pt α =0.00392 (1/℃).
R₁=R₀[1+α(T₁T₀)]
R₂= R₀[1+α(T₂T₀)]
R₁/R₂=[1+α(T₁T₀)]/[1+α(T₂T₀)]
200/253.8=(1 0.00392 •20)/[1+ 0.00392• (T₂20)]
Solving for T₂ gives
T₂=63.2℃