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43.

The time constant of a thermocouple is

A.	the time taken to attain the final temperature to be measured	B.	the time taken to attain 50% of the value of initial temperature difference
C.	the time taken to attain 63.2% of the value of initial temperature difference	D.	determined by the time taken to reach 100°C from 0°C

44.

The unit of overall coefficient of heat transfer is

A.	kcal/m2	B.	kcal/hr °C
C.	kcal/m2 hr °C	D.	kacl/m hr °C

45.

The unit of Stefan Boltzmann constant is

A.	watt/cm2 °K	B.	watt/cm4 °K
C.	watt2/cm °K4	D.	watt/cm2 °K4

46.

The value of Portland number for air is about

A.	0.1	B.	0.3
C.	0.7	D.	1.7

47.

Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of

A.	0.002	B.	0.02
C.	0.01	D.	0.1

48.

Thermal conductivity of air with rise in temperature

A.	increases	B.	decreases
C.	remains constant	D.	may increase or decrease depending on temperature

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