Q. The readings of a constant volume gas thermometer at 0${^\circ}$C and 100${^\circ}$C are 40cm of mercury and 60 cm of mercury. If its reading at an unknown temperature is 100cm of mercury column, then the temperature is
A) 100${^\circ}$C
B) 50${^\circ}$C
C) 25${^\circ}$C
D) 300${^\circ}$C
Explanation
(d) Pressure at $0℃,\ p_{0} = \ 40\ cm$
Pressure at $100℃,\ p_{100} = \ 60\ $cm
Pressure at unknown temperature t,
$p_{t}$=100 cm of mercury. Then
$t = 100\left( \frac{p_{t} - p_{0}}{p_{100} - p_{0}} \right)$
$= \ 100\left( \frac{100 - 40}{60 - 40} \right) = 300^{o}C$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.