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

0.043055555555556

0.042361111111111

0.16736111111111

0.084027777777778

0.043055555555556

0.042361111111111

0.16736111111111

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Heat and Mass Transfer
When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

α = 0, ρ = 0 and τ = 1

α = 1, ρ = 0 and τ = 0

α = 0, ρ = 1 and τ = 0

α + ρ = 1 and τ = 0

α = 0, ρ = 0 and τ = 1

α = 1, ρ = 0 and τ = 0

α = 0, ρ = 1 and τ = 0

α + ρ = 1 and τ = 0

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Heat and Mass Transfer
An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

40 mm

800 mm

25 mm

160 mm

40 mm

800 mm

25 mm

160 mm

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Heat and Mass Transfer
The emissive power of a body depends upon its

Temperature

Physical nature

Wave length

All of these

Temperature

Physical nature

Wave length

All of these

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Heat and Mass Transfer
Heat transfer takes place as per

Zeroth law of thermodynamics

Second law of the thermodynamics

Kirchoff's law

First law of thermodynamic

Zeroth law of thermodynamics

Second law of the thermodynamics

Kirchoff's law

First law of thermodynamic

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Heat and Mass Transfer
Heat transfer by radiation mainly depends upon

Its temperature

All of these

Kind and extent of its surface

Nature of the body

Its temperature

All of these

Kind and extent of its surface

Nature of the body

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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 When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

Heat and Mass Transfer An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

Heat and Mass Transfer The emissive power of a body depends upon its

Heat and Mass Transfer Heat transfer takes place as per

Heat and Mass Transfer Heat transfer by radiation mainly depends upon

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
When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

Heat and Mass Transfer
An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

Heat and Mass Transfer
The emissive power of a body depends upon its

Heat and Mass Transfer
Heat transfer takes place as per

Heat and Mass Transfer
Heat transfer by radiation mainly depends upon