Heat Transfer - Mechanical Engineering Multiple Choice Questions and Answers for competitive exams

1. Unit of thermal conductivity in M.K.S. units is
(a) kcal/kg m2 °C
(b) kcal-m/hr m2 °C
(c) kcal/hr m2 °C  
(d) kcal-m/hr °C
(e) kcal-m/m2 °C.

Ans: b

2. Unit of thermal conductivity in S.I. units is
(a) J/m2 sec   
(b) J/m °K sec
(c) W/m °K   
(d) (a) and (c) above
(e) (b) and (c) above.

Ans: e

3.     Thermal conductivity of solid metals with rise in temperature normally
(a)     increases   
(b)     decreases
(c)    remains constant
(d)    may increase or decrease depending on temperature
(e)    unpredictable.

Ans: b

4. Thermal conductivity of non-metallic amorphous solids with decrease in temperature
(a)     increases   
(b)     decreases
(c)     remains constant
(d)    may increase or decrease depending on temperature
(e)    unpredictable.

Ans: b

5.     Heat transfer takes place as per -
(a)     zeroth law of thermodynamics
(b)    first law of thermodynamic
(c)    second law of the thermodynamics
(d)    Kirchhoff law (e) Stefan's law.

Ans: c

6.  When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by
(a)     conduction      
(b)     convection
(c)     radiation
(d)    conduction and convection
(e)    convection and radiation.

Ans: a

7.    When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by
(a)     conduction      
(b)     convection
(c)     radiation
(d)    conduction and convection
(e)    convection and radiation.
Ans: c

8.    Sensible heat is the heat required to
(a)    change vapour into liquid
(b)    change liquid into vapour
(c)    increase the temperature of a liquid of vapour
(d)    convert water into steam and superheat it
(e)    convert saturated steam into dry steam.
Ans: c

9.    The insulation ability of an insulator with the presence of moisture would
(a) increase   
(b) decrease
(c)    remain unaffected
(d)    may increase/decrease  depending  on temperature and thickness of insulation
(e)    none of the above.
Ans: b

10.    When heat is Transferred by molecular collision, it is referred to as heat transfer by
(a) conduction      
(b) convection
(c) radiation   
(d) scattering
(e) convection and radiation.   
Ans: b

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