21.
Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in
A
steam condenser
B
melting of ice
C
boiler.
D
electric heater
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Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in
steam condenser
melting of ice
boiler.
electric heater
Thermal diffusivity of a substance is
inversely proportional to density of substance
inversely proportional to specific heat
all of the above
directly proportional to thermal con¬ductivity
The amount of heat flow through a body by conduction is
directly proportional to the temperature difference on the two faces of the body
dependent upon the material of the body
all of the above.
directly proportional to the surface area of the body
Heat flows from one body to other when they have
different specific heat
different atomic structure
different temperatures
different heat contents
Heat transfer in liquid and gases takes place by
convection
radiation
conduction and convection
conduction
When heat is Transferred by molecular collision, it is referred to as heat transfer by
convection
radiation
scattering
conduction
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
convection
radiation
conduction and convection
conduction
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
convection
radiation
conduction and convection
conduction
Thermal conductivity of glass-wool varies from sample to sample because of variation in
density
porosity
all of the above.
composition
Total heat is the heat required to
change liquid into vapour
increase the temperature of a liquid or vapour
convert water into steam and superheat it
change vapour into liquid
Sensible heat is the heat required to
change liquid into vapour
increase the temperature of a liquid of vapour
convert water into steam and superheat it
change vapour into liquid
Which of the following is the case of heat transfer by radiation
heating of building
cooling of parts in furnace
heat received by a person from fireplace
blast furnace
Which of the following has maximum value of thermal conductivity
steel
brass
copper
aluminium
Thermal diffusivity is
function of temperature
used as mathematical model
a physical property of the material
a dimensionless parameter