The insulation ability of an insulator with the presence of moisture would_________________?

Related Mcqs:

1. Moisture would find its way into insulation by vapour pressure unless it is prevented by __________________ ?

   A. high thickness of insulation
   B. high vapour pressure
   C. less thermal conductivity insulator
   D. a vapour seal
   E. all of the above

2. Cork is a good insulator because it has___________________?

   A. free electrons
   B. atoms colliding frequency
   C. low density
   D. porous body
   E. all of the above

3. 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

4. Which of the following is a case of steady state heat transfer ___________________?

   A. I.C. engine
   B. air preheaters
   C. heating of building in winter
   D. all of the above
   E. none of the above

5. Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in _________________?

   A. electric heater
   B. steam condenser
   C. melting of ice
   D. refrigerator condenser coils
   E. boiler

6. Thermal conductivity of wood depends on_______________?

   A. moisture
   B. density
   C. temperature
   D. all of the above
   E. none of the above

7. Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of____________________?

   A. 1 :1
   B. 2: 1
   C. 1 : 2
   D. 4 : 1
   E. 1 : 4

8. The value of Prandtl number for air is about _______________________?

   A. 0.1
   B. 0.3
   C. 0.7
   D. 1.7
   E. 10.5

9. Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by ___________________?

   A. convection
   B. free convection
   C. forced convection
   D. radiation
   E. radiation and convection

10. According to Wien’s law, the wavelength corresponding to maximum energy is proportion to ________________?

    A. absolute temperature (T)
    B. I2
    C. f
    D. t
    E. 1/r