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Q.. \ .. The trip\e -points of neon and carbon dioxide are 24.57 Kand 216.55 K resp ectively E..,., , press, these temperatures on Cel sius and Fahrenheit scales., A.ns. Ghren T Ne = 2A.51 'K., T CO2= 216.55 K ", ,,., (.i) Ce\sius scale: \ft is the temperature on Celsius scale and T the corresponding temperature, on K..e\vin sca\e, t.ben, t = T-273.15, tNe = 24.57 - 273.15 = -248.58°C, tco2 = 216.55 -273.15 = - 56.6°C, ., (ii) Fahrenheit scale~ lf ° F is temperature on Fahrenheit scale and TK the corresponding, t.emperature on Kelvin scale, then, •, , F-32, T-273.15, 18() 100, , 76 \ Physics-'X.\: 1erm- 2, , ~, , F, , = 32 + ~, J, , (T-273.15), , 4
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F Ne :::, , :::, , 32, 32, , 9, , + 5 (24.57 -, , 273. 15), , - I x 248.58 == 32 - 44 7.44 = - 415.44 °F, , 9, F.co, ::: 32 + 5, (216.55 - 273.15), , = 32 - }x56.6 = 32 - 101.88 = - 69.88°F, , Q,2, Answer the following:, , (a) The triple point of water is 8 sta d d, wrong in taking the melting p .n a~. fixed point in modern thermometry. Why? What is, Points?, oint O ice and the boiling point of water as standard fixed, , (b) There are two fixed points on th C ., and l00°C respectively. On the ;el e.1s:us scale which have been assigned the number _0°C, Point of water: which on th K . vm s absolute scale, one of the fixed point is the triple, 1, is the other fi~ed po'10t, eh' e vm a~solute scale is assigned the number 273.16 K. What, on t ts (Kelvm) scale?, (c) Thale abbsoluteTtem pe rature on (Kelvin) scale Tis related to the temperature t on Celsius, sc e y tc = - 273.15, c, Why do we have 273.15 in this relation and not 273.16?, , (cl) What is the temperature of the triple point of water on an absolute scale whose unit interval, is equal to that of Fahrenheit scale?, Ans, (a) The triple point of water is chosen as standard fixed point because it is unique. It means that, , it oc~urs ar_ temp~rature 27_3.16 Kand pressure 0.46 mm of Hg only. On the other hand,, meltmg pomt of ICe and b01ling point of water are not unique; they change with change of, pressure., (b) The other fixed point on Kelvin's scale is the absolute zero temperature (T = 0)., (c) Given relation, t, = T - 273.15 is the conversion relation between Celcius scale and absolute, scale. 273.15 is the absolute temperature on Kelvin's scale corresponding to 0°C on Celcius, scale; while 273.16 is the triple point of water which corresponds to °C (and not to 0°C) on, Celcius scale., , (d) On absolute (or Kelvin scale) and also on Celsius scale the interval between ice-point and, steam-point has been divided into 100 equal parts; while on Fahrenheit scale this interval, has been divided into 180 equal parts. Therefore, the size of one degree on Kelvin absolute, , scale is, , !~~ = 1.8 times that on Fahrenheit scale. The temperature of triple point of water, , on absolute scale is 273.16 K. If the size of degree on absolute scale is made equal to that on, Fahrenheit scale, then triple point of water on this new scale will be 273.16 x 1.8 = 49 l .69°F., , Q. S., , Two ideal gas thermometers A and B use oxygen and hydrogen respectively. The following, , observations are made:, , A, 5, , Pressure thennometer B, , Triple point of water, , l .250 x l 0 Pa, , 0.200 x l 05 Pa, , Normal melting point of sulphur, , l.797 x 105 Pa, , 0.287 x 105 Pa, , (a) What is the absolute temperature of normal melting point of sulphur as read, , by, , thermometers A and B?, , (b) What do you think is the reason behind the slight difference in answers of thermometers, A lad B? (The thennometen are not faulty). What further procedure is needed in the, tlferiment to reduce the discrepancy between the two readings?, !,le point of water, T0 = 273.15 K., ., ometer A,, , T.4 = PA, To Po, , where suffix Orefers to triple point, , Thermal Properties of Matter 77
