Home › ACSEE (Form 6) › Physics › Heat (Thermometers and First Law of Thermodynamics) › Temperature on a resistance thermometer scale is…
Temperature on a resistance thermometer scale is obtained from:
A$\theta=\dfrac{R_\theta-R_{100}}{R_0-R_{100}}\times100$
B$\theta=\dfrac{R_{100}-R_0}{R_\theta-R_0}\times100$
C$\theta=\dfrac{R_\theta+R_0}{R_{100}+R_0}\times100$
D$\theta=\dfrac{R_\theta-R_0}{R_{100}-R_0}\times100$
Answer & Solution
Correct answer: D. $\theta=\dfrac{R_\theta-R_0}{R_{100}-R_0}\times100$
1. The scale is fixed by two reference points, the ice point and the steam point.
2. $R_0$ is the resistance at the ice point and $R_{100}$ at the steam point.
3. The numerator $R_\theta-R_0$ measures how far the reading has risen above the ice point.
4. The denominator $R_{100}-R_0$ is the full span between the two fixed points.
5. That ratio, multiplied by 100, gives the temperature in degrees on this scale; inverting the fraction would make higher resistance read as a lower temperature.
_Source: NECTA ACSEE 2023 Physics 131/1, Question 5:Heat (Thermometers and First law of Thermodynamics)_