The radiation emitted by a black body is known as All of these Black radiation Total radiation Full radiation TRUE ANSWER : ? YOUR ANSWER : ?
According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the Fourth power of the absolute temperature Square of the absolute temperature Cube of the absolute temperature Absolute temperature TRUE ANSWER : ? YOUR ANSWER : ?
Absorptivity of a body will be equal to its emissivity At critical temperature When system is under thermal equilibrium At one particular temperature At all temperatures TRUE ANSWER : ? YOUR ANSWER : ?
Planck’s law holds good for All of these all coloured bodies black bodies polished bodies TRUE ANSWER : ? YOUR ANSWER : ?
Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of 0.1 0.02 0.002 0.01 TRUE ANSWER : ? YOUR ANSWER : ?
The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit) tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) TRUE ANSWER : ? YOUR ANSWER : ?
Thermal conductivity of non-metallic amorphous solids with decrease in temperature Remain constant Increases Decreases May increase or decrease depending on temperature TRUE ANSWER : ? YOUR ANSWER : ?
The thermal diffusivities for gases are generally More than those for solids Dependent on the viscosity Less than those for liquids More than those for liquids TRUE ANSWER : ? YOUR ANSWER : ?
The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as Thermal coefficient Thermal conductivity None of these Thermal resistance TRUE ANSWER : ? YOUR ANSWER : ?
In heat exchangers, degree of approach is defined as the difference between temperatures of Hot medium outlet and cold water inlet Hot medium inlet and outlet Hot medium outlet and cold water outlet Cold water inlet and outlet TRUE ANSWER : ? YOUR ANSWER : ?