When holes are dug into the Earth, it is found that for a depth of every 30 m, the temperature rises by `1^@C`.
If the coefficient of conductivity of Earth's crust is 0.8 `watt//m^@k`, calculate the amount of heat flowing through an area of 1 sq. metre on surface of earth, per minute

Calculate the rate of loss of heat through a glass window of area 1000 cm2 and thickness of 4 mm, when temperature inside is 27^@ C and outside is -5^@ C . Coefficient of thermal conductivity of glass is 0.022 cal/ s cm^@ C.

The difference in temperature between two sides of a glass plate 0.3 mm thick is 25^@C . If the area of one side surface is 10 m^2 , calculate the heat conducted per second through the plate. The thermal conductivity of glass is 0.84 J//s m K.

The door of a refrigerator is 150 cm. high, 80 cm wide and 6 cm thick. If the coefficient of thermal conductivity is 5 xx 10^-4 cal//cm . s. ^@C and the inner and outer surfaces are at 0^@C and 30^@C respectively. Calculate heat loss through the door in 1 minute.

Answer the following : An aluminium sheet of area 0.1 m^2 , initially at temperature 30 ⁰C is heated such that it reaches the temperature of 70 ⁰C . If the coefficient of areal expansion of aluminium is 46.2 x 10^-6 (1/⁰C) , find the change in area of the sheet .

The thermal conductivity of steel is 0.026 k cal//ms K. Find the temperature diference between two sides of a steel plate 4 cm thick, when heat is transmitted through the plate at the rate of 400 k cal per minute per squar metre of steady state.

An ice box used for keeping cold eatables has a total wall area of 1 metre^2 and a wall thickness of 5.0 cm. The thermal conductivity of the ice box is K=0.01 (jou l e)/(metre)^@C . It is filled with ice at 0^@C along with eatables on a day when the temperature is 30^@C . The latent heat of fusion of ice is 334 x 10^3 joules/kg. The amount of ice melted in one day is (1 day = 86,400 seconds)

When 0.1 kg of ice at 0 ^@C is mixed with 0.32 kg of water at 35 ^@C in a container. The resulting temperature of the mixture is 7.8 ^@C . Calculate the heat of fusion of ice (S_water = 4186 J kg^-1 K^-1)

A body having a surface area of 50cm^2 radiates 300J of energy per minute at a temperature of 727^(@)C . The emissivity of the body is ( Stefan's constant =5.67xx10^(-8)W//m^2K^4 )

A metal ball of surface area 200 cm^(2) and temperature 527^(@)C is surrounded by a vessel at 27^(@)C . If the emissivity of the metal is 0.4, then the rate of loss of heat from the ball is (sigma = 5.67 xx10^(-8)J//m^(2)-s-k^(4))

A 100 watt filament loses all its power by radiation when it is heated to a temperature of 2500 K. If the diameter of the filament is 0.2 mm and the surface emissivity of the filament is 0.5, find the length of the filament. (Stefan's constant sigma = 5.67 xx10^-8 W/m^2k^4 )