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

Heat and Mass Transfer
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

0.084027777777778

0.16736111111111

0.043055555555556

0.042361111111111

0.084027777777778

0.16736111111111

0.043055555555556

0.042361111111111

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Heat and Mass Transfer
Which of the following property of air does not increase with rise in temperature?

Thermal diffusivity

Thermal conductivity

Density

Dynamic viscosity

Thermal diffusivity

Thermal conductivity

Density

Dynamic viscosity

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Heat and Mass Transfer
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a

Grey body

White body

Black body

Opaque body

Grey body

White body

Black body

Opaque body

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Heat and Mass Transfer
According of Kirchhoff's law

Radiant heat is proportional to fourth power of absolute temperature

Emissive power and absorptivity are constant for all bodies

Emissive power depends on temperature

Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body

Radiant heat is proportional to fourth power of absolute temperature

Emissive power and absorptivity are constant for all bodies

Emissive power depends on temperature

Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body

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Heat and Mass Transfer
Thermal conductivity of wood depends on

All of these

Temperature

Moisture

Density

All of these

Temperature

Moisture

Density

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Heat and Mass Transfer
Heat transfer in liquid and gases takes place by

Conduction and convection

Radiation

Conduction

Convection

Conduction and convection

Radiation

Conduction

Convection

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Heat and Mass Transfer

Heat and Mass Transfer 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

Heat and Mass Transfer Which of the following property of air does not increase with rise in temperature?

Heat and Mass Transfer When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a

Heat and Mass Transfer According of Kirchhoff's law

Heat and Mass Transfer Thermal conductivity of wood depends on

Heat and Mass Transfer Heat transfer in liquid and gases takes place by

Heat and Mass Transfer
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

Heat and Mass Transfer
Which of the following property of air does not increase with rise in temperature?

Heat and Mass Transfer
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a

Heat and Mass Transfer
According of Kirchhoff's law

Heat and Mass Transfer
Thermal conductivity of wood depends on

Heat and Mass Transfer
Heat transfer in liquid and gases takes place by