Deck 1: Thermal Conductivity and Heat Transfer

Question 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.

Answer 1

kcal-m/hr m² °C

Question 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.

Answer 2

b and c above.

Question 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)uN_Predictable.

Answer 3

decreases

Question 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)uN_Predictable.

Question 5

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.

Question 6

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.

Question 7

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.

Question 8

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.

Question 9

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.

Question 10

Heat transfer in liquid and gases takes place by

A)conduction
B)convection
C)radiation
D)conduction and convection
E)convection and radiation.

Question 11

Which of the following is the case of heat transfer by radiation

A)blast furnace
B)heating of building
C)cooling of parts in furnace
D)heat received by a person from fireplace
E)all of the above.

Question 12

Heat is closely related with

A)liquids
B)energy
C)temperature
D)entropy
E)enthalpy.

Question 13

Pick up the wrong case. Heat flowing from one side to other depends directly on

A)face area
B)time
C)thickness
D)temperature difference
E)thermal conductivity.

Question 14

Metals are good conductors of heat because

A)their atoms collide frequently
B)their atoms-are relatively far apart
C)they contain free electrons
D)they have high density
E)all of the above.

Question 15

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.

Question 16

Total heat is the heat required to

A)change vapour into liquid
B)change liquid into vapour
C)increase the temperature of a liquid or vapour
D)convert water into steam and superheat it
E)convert saturated steam into dry steam.

Question 17

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.

Question 18

Thermal conductivity of water in general with rise in temperature

A)increases
B)decreases
C)remains constant
D)may increase or decrease depending on temperature
E)none of the above.

Question 19

Thermal conductivity of water at 20°C is of the order of

A)0.1
B)0.23
C)0.42
D)0.51
E)0.64.

Question 20

Temperature of steam at around 540°C can be measured by

A)thermometer
B)radiatiouv pyrometer
C)thermistor
D)thermocouple
E)thermopile.

Question 21

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
E)0.5.

Question 22

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
E)none of the above.

Question 23

Thermal conductivity of air with rise in temperature

A)increases
B)decreases
C)remains constant
D)may increase or decrease depending on temperature
E)none of the above.

Question 24

Heat flows from one body to other when they have

A)different heat contents
B)different specific heat
C)different atomic structure
D)different temperatures
E)none of the above.