Heat and Mass Transfer
Kirchhoff's law states that

The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
The wave length corresponding to the maximum energy is proportional to the absolute temperature
The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
None of these

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Heat and Mass Transfer
Thermal conductivity of a material may be defined as the

Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
All of these
Quantity of heat flowing in one second through one cm cube of material when opposite faces are 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

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