Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)
h = k/ ρS
h = ρS/k
h = S/ρk
h = kρ/S
Correct Answer :
A. h = k/ ρS
Related Questions
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Convection
Radiation
Forced convection
Free convection
The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit
Temperature
Thickness
Area
Time
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Nature of the body
Temperature of the body
Type of surface of the body
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Grey body
Opaque body
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Square of the absolute temperature
Cube of the absolute temperature
Fourth power of the absolute temperature
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In heat exchanger design as a safety factor
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Greater than one
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Biot number
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0.1
0.23
0.42
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Directly proportional to thermal conductivity
Inversely proportional to density of substance
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Decreases
Remain constant
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P=1, x = 0 and a = 0
P = 0, x = 1 and a = 0
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α = 0, ρ = 1 and τ = 0
α = 0, ρ = 0 and τ = 1
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Total radiation
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Liquids
Energy
Temperature
Entropy
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Maximum
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Zero
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Wien's law
Stefan's law
Kirchhoff's law
Planck's law
The value of the wave length for maximum emissive power is given by
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Stefan's law
Wines law
Planck's law
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Boiler furnaces
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None of these
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
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Transmissivity
Reflectivity
Intensity of radiation
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Higher
More or less same
Very much lower
Planck's law holds good for
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Polished bodies
All coloured bodies
All of the above
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Thermal coefficient
Temperature gradient
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Condensers and boilers in steam plants
Condensers and evaporators in refrigeration and air conditioning units
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Convection
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Liquids
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One dimensional cases only
Two dimensional cases only
Three dimensional cases only
Regular surfaces having non-uniform temperature gradients