Demonstration of Difference in Values of Temperature for Thermometers Based on Different Thermometric Properties
Mark for 100 °C Mark for 0 °C Mark for 0 °C
Steam
Melting ice
Boiling water Hotplate (a) Beaker of melting ice
(b) Flask of boiling water Fig 8.8
(c) Beaker of warm water
Apparatus Platinum wire and ohmmeter, ungraduated mercury thermometer and ruler, beaker of melting ice, flask of boiling water on a hotplate, beaker of warm water
Procedure ■ Set up apparatus as illustrated in Fig 8.8(a). Measure the length of the column of mercury in ice (lice) and the resistance of the platinum wire in ice (Rice).
■ Set up apparatus as illustrated in Fig 8.8(b). Measure the length of the column of mercury in steam (lsteam) and the resistance of the platinum wire in steam (Rsteam).
■ Set up apparatus as illustrated in Fig 8.8(c). Measure the length of the column of mercury in the warm water (lwater) and the resistance of the platinum wire in the warm water (Rwater).
■ On graph paper plot the points (l ice, 0) and (l steam, 100) and draw a straight line connecting the points. Use your graph to find the temperature that corresponds to lwater.
■ On a second graph plot the points (Rice, 0) and (Rsteam,100) and draw a straight line connecting the points.Use your graph to find the temperature that corresponds to Rwater.
Observation The value for the temperature of the warm water differs depending on which graph is used.
Conclusion No one thermometer gives a true value for temperature.
14 12 10 8 6
2 4
0 0 20 40 60 / °C (a) Resistance versus temperature 80 100 120
120 100 80 60
20 40
0 0 20 40 60 / °C (b) Height versus temperature
Fig 8.9: Sample graphs with (a) showing a temperature of 19.5C while (b) shows a temperature of 20.5C for the beaker of warm water
