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There were two fixed points in the original Celsius scale as mentioned above which were assigned the number 0 °C and 100 °C respectively. On the absolute scale, one of the fixed points is the triple-point of water, which on the Kelvin absolute scale is assigned the number 273.16 K. What is the other fixed point on this (Kelvin) scale?

The absolute zero or 0 K is the other fixed point on the Kelvin absolute scale.
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The triple points of neon and carbon dioxide are 24.57 K and 216.55 K respectively. Express these temperatures on the Celsius and Fahrenheit scales.

Kelvin and Celsius scales are related as: 

TC = TK – 273.15                  … (i) 

Celsius and Fahrenheit scales are related as: 

TF = (9/5)TC + 32                ...(ii)


For neon: 

TK = 24.57 K 

 T= 24.57 – 273.15 = –248.58°C 

TF = (9/5)TC + 32 

    = (9/5) × (-248.58) +32 

    = 415.440 F

For carbon dioxide:

TK = 216.55 K 

 TC= 216.55 – 273.15

     = –56.60°C 

TF = (9/5)TC + 32 

    = (9/5) × (-56.60) +32 

    = -69.880 C
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Two absolute scales A and B have triple points of water defined to be 200 A and 350 B. What is the relation betweenTA and TB?

Triple point of water on absolute scale A, T1 = 200 A

Triple point of water on absolute scale B, T2 = 350 B

Triple point of water on Kelvin scale, TK = 273.15 K

The temperature 273.15 K on Kelvin scale is equivalent to 200 A on absolute scale A.

           T1 = T

      200 A = 273.15 K 

∴          A = 273.15/200 

The temperature 273.15 K on Kelvin scale is equivalent to 350 B on absolute scale B. 

          T2 = T

     350 B = 273.15

∴        B = 273.15/350 

TA is triple point of water on scale A. 

TB is triple point of water on scale B. 

∴         273.15/200 × T = 273.15/350 × T

Therefore, the ratio TA : Tis given as 4 : 7
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The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?

The triple point of water has a unique value of 273.16 K. At varying values of volume and pressure, the triple point of water is always 273.16 K.

The melting point of ice and boiling point of water do not have particular values because these points depend on pressure and temperature.
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The electrical resistance in ohms of a certain thermometer varies with temperature according to the approximate law: 

                  R Ro [1 + α (– To)] 

The resistance is 101.6 Ω at the triple-point of water 273.16 K, and 165.5 Ω at the normal melting point of lead (600.5 K). What is the temperature when the resistance is 123.4 Ω?


Given that, 


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