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Engineering :: Heat Transfer


81.  The surface temperature of the sun is
A. 2000?K B. 6000?K
C. 20000?K D. Millions of degrees
E. Infinitely large    

82.  Tea pots are highly polished
A. So that they may not conduct heat from outside B. So that they may absorb all radiation from outside
C. To make them attractive to look at D. Because porcelain takes high polish
E. None of the above    

83.  A perfect black body is the one which
A. Absorbs all incident radiation B. Reflects all incident radiation
C. Absorbs most of the incident radiation D. Is coated with lamp black

84.  What whould be shape of an ideal thermometer?
A. Spherical B. Cylindrical
C. Cubical D. Rectangular

85.  A Foreman of an automobile workshop wants to measure the temperature inside the piston of a car, whose temperature will be of the order of 700?C (accurate upto 1?C). The best thermometer to use is
A. Platinum resistance thermometer B. Thermo electric thermometer
C. Constant volume hydrogen thermometer D. Constant volume nitrogen thermometer
E. Optical pyrometer    

86.  In constant volume Hydrogen gas Thermometer, a correction has to be applied, because
A. Hydrogen is impure B. Expansion of Hydrogen is non-linear
C. Density of mercury changes D. None of the above

87.  When metallic surfaces are oxidized the emissivity
A. Increases B. Decreases
C. Does not change D. Depends on the temperature
E. Depends on other factors    

88.  If a body reflects entire radiation incident on it, then it is known as
A. Black body B. Grey body
C. White body D. Transparent body
E. Opaque body    

89.  Two parallel opposed, infinite black planes are maintained at 300?C and 400?C respectively. If the temperature difference is doubled by increasing the temperature from 400?C to 500?C, the heat exchange rate will increase by a factor of about
A. 2.5 B. 4.5
C. 5.5 D. 6.25
E. 8.75    

90.  Which is the unit of Stefan Boltzmann constant
A. W/m2 K4 B. erg/cm2-sec-K4
C. cal/cm2-sec K4 D. kcal/m2-hr-K4
E. All of the above    




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