A thermometer can be read to an accuracy of ± 0.5 °C. This thermometer is used to measure a temperature rise from 40 °C to 100 °C.

Question 26

A thermometer can be read to an accuracy of ± 0.5 °C. This thermometer is used to measure a temperature rise from 40 °C to 100 °C.

What is the percentage uncertainty in the measurement of the temperature rise?

A 0.5 %                       B 0.8 %                       C 1.3 %                       D 1.7 %

Reference: Past Exam Paper – November 2003 Paper 1 Q4 & June 2014 Paper 12 Q5

Solution:

Answer: D.

Initial temperature: T₁ = 40 °C

Final temperature: T₂ = 100 °C

Temperature rise: T = T₂ – T₁ = 100 – 40 = 60 °C

The measurement of both the initial and final temperatures have an uncertainty of ± 0.5°C.

ΔT = ΔT₂ + ΔT₁

ΔT = 0.5 + 0.5 = 1.0 °C

Percentage uncertainty in the measurement of the temperature rise:

%uncertainty in T = [ΔT / T] × 100%

%uncertainty in T = (1/60) × 100% = 1.7%