A platinum resistance thermometer has resistances of 1500 oh

A platinum resistance thermometer has resistances of 150.0 ohm when placed in a 0 degree C ice bath and 239.8 ohm when immersed in a crucible containing a melting substance. What is the melting point of this substance?

Solution

R = R₀ [1 + alpha (T - T₀)]

R₀ = 150 / [1 +(3.92 * 10^-3) (0 - 20)]

= 162.76 ohms

R\' = R₀ [1 + alpha (T\' - T₀)]

T\' = [R\' / R₀ - 1] / alpha + T₀

= [239.8 / 162.76 - 1 ] / (3.92 * 10^-3) + 20

= 140.75 ⁰C