## A body cools from 80 oC to 50 oC in 5 minutes. Calculate the time it takes to cool from 60 oC to 30 oC . The tempera ture of the surroundings is 20 oC .

A body cools from 80 oC to 50 oC in 5 minutes. Calculate the time it takes to cool from 60 oC to 30 oC . The tempera ture of the surroundings is 20 oC .

## Explain why: a body with large reflectivity is a poor emitter   a brass tumbler feels much c older than a wooden tray on a chilly day an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body radiation gives too low a value for the temperature of a red hot iron piece in the open, but gives a correct value for the temperature when the same piece is in the furnace the earth without its atmosphere would be inhospitably cold heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water

Explain why: a body with large reflectivity is a poor emitter   a brass tumbler feels much c older than a wooden tray on a chilly day an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body radiation gives Read More …

## A brass boiler has a base area of 0.15 m2 and thickness 1.0 cm. It boils water at the rate of 6.0 kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler. Thermal conductivity of brass =109 J s-1 m-1 K-1 ;Heat of vaporisation of water =2256 × 103 J kg-1.

A brass boiler has a base area of 0.15 m2 and thickness 1.0 cm. It boils water at the rate of 6.0 kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the Read More …

## A ‘thermacole’ icebox is a cheap and efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0 cm. If 4.0 kg of ice is put in the box, estimate the amount of ice remaining after 6 h. The outside temperature is 45oC , and co-efficient of thermal conductivity of thermacole is  0.01 J s-1 m-1 K-1 .[Heat of fusion of water =335×103J kg-1]

A ‘thermacole’ icebox is a cheap and efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0 cm. If 4.0 kg of ice is put in the Read More …

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