Equal to one
Greater than one
Less than one
Equal to Nusselt number
A. Equal to one
Thermal resistance
Thermal coefficient
Temperature gradient
Thermal conductivity
Glass
Water
Plastic
Air
0.1
0.23
0.42
0.51
Stanton number
Biot number
Peclet number
Grashoff number
Maximum
Minimum
Zero
None of these
Equivalent thickness of film
Thermal conductivity Equivalent thickness of film Specific heat × Viscosity
Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
Film coefficient × Inside diameter Thermal conductivity
Conduction
Convection
Radiation
None of these
Grashoff number
Nusselt number
Weber number
Prandtl number
kcal/m²
kcal/hr °C
kcal/m² hr °C
kcal/m hr °C
Moisture
Density
Temperature
All of the above
Absolute temperature
Square of temperature
Fourth power of absolute temperature
Fourth power of temperature
tm = (Δt1 - Δt2)/ loge (Δt1/Δt2)
tm = loge (Δt1/Δt2)/ (Δt1 - Δt2)
tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2)
tm = loge (Δt1 - Δt2)/ Δt1/Δt2
Shorter wavelength
Longer wavelength
Remain same at all wavelengths
Wavelength has nothing to do with it
0
0.5
0.75
1
Thermal coefficient
Thermal resistance
Thermal conductivity
None of these
Convection
Radiation
Forced convection
Free convection
It is impossible to transfer heat from low temperature source to t high temperature source
Heat transfer by radiation requires no medium
All bodies above absolute zero emit radiation
Heat transfer in most of the cases takes place by combination of conduction, convection and radiation
Temperature
Wave length
Physical nature
All of the above
Directly proportional to the surface area
Directly proportional to the difference of temperatures between the two bodies
Either (A) or (B)
Both (A) and (B)
Absolute temperature (T)
I²
F
T
Absorptive power
Emissive power
Absorptivity
Emissivity
Different heat contents
Different specific heat
Different atomic structure
Different temperatures
Iron
Lead
Concrete
Wood
P = 0, x = 0 and a = 1
P= 1, T = 0 and a = 0
P = 0, x = 1 and a = 0
X = 0, a + p = 0 Where a = absorptivity, p = reflectivity, X = transmissivity.
Quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
Quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
All of the above
Below which a gas does not obey gas laws
Above which a gas may explode
Below which a gas is always liquefied
Above which a gas will never liquefied
Conduction
Convection
Radiation
Conduction and convection
A grey body is one which absorbs all radiations incident on it.
At thermal equilibrium, the emissivity and absorptivity are same.
The energy absorbed by a body to the total energy falling on it, is called emissivity.
A perfect body is one which is black in colour.
Conduction
Convection
Radiation
Conduction and radiation combined
Their atoms collide frequently
Their atoms are relatively far apart
They contain free electrons
They have high density