## 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 …

## A child running a temperature of 101oF is given an antipyrin (i.e. a medicine that lowers    fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to 98 o F in 20 min, what is the average rate of extra evaporation caused, by the drug? Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the child is 30 kg. The specific heat of human body is approximately the same as that of water, and latent heat of evaporation of water at that temperature is about   580 cal g-1 .

A child running a temperature of 101oF is given an antipyrin (i.e. a medicine that lowers    fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to 98 o F Read More …

## Answer the following questions based on the P–T phase diagram of  CO2 :  CO2 at 1 atm pressure and temperature – 60 oC is compressed isothermally. Does it go through a liquid phase? What happens when  CO2 at 4 atm pressure is cooled from room temperature at constant pressure? Describe qualitatively the changes in a given mass of solid  CO2 at 10 atm pressure and temperature – 65 oC as it is heated up to room temperature at constant pressure.  CO2 is heated to a temperature 70 oC and compressed isothermally. What changes in its properties do you expect to observe?

Answer the following questions based on the P–T phase diagram of  CO2 : CO2 at 1 atm pressure and temperature – 60 oC is compressed isothermally. Does it go through a liquid phase? What happens when  CO2 at 4 atm pressure Read More …

## Answer the following questions based on the P-T phase diagram of carbon dioxide: At what temperature and pressure can the solid, liquid and vapour phases of  CO2 co-exist in equilibrium? What is the effect of decrease of pressure on the fusion and boiling point of  CO2 ? What are the critical temperature and pressure for CO2 ?What is their significance? Is  CO2 solid, liquid or gas at (a) – 70 oC under 1 atm, (b) – 60 oC under 10 at m, (c) 15 oC under 56 atm?

Answer the following questions based on the P-T phase diagram of carbon dioxide: At what temperature and pressure can the solid, liquid and vapour phases of  CO2 co-exist in equilibrium? What is the effect of decrease of pressure on the fusion Read More …

## Given below are observations on molar specific heats at room temperature of some common gases.

Given below are observations on molar specific heats at room temperature of some common gases.

## In an experiment on the specific heat of a metal, a 0.20 kg block of the metal at 150 oC is dropped in a copper calorimeter (of water equivalent 0.025 kg) containing 150 cm3 of water at 27 oC . The final temperature is 40 oC . Compute the specific heat of the metal. If heat losses to the surroundings are not negligible, is your answer greater or smaller than the actual value for specific h eat of the metal?

In an experiment on the specific heat of a metal, a 0.20 kg block of the metal at 150 oC is dropped in a copper calorimeter (of water equivalent 0.025 kg) containing  150 cm3 of water at 27 oC . The final Read More …

## A copper block of mass 2.5 k g is heated in a furnace to a temperature of 500 oC and then placed on a large ice block. What is the maximum amount of ice that can melt? (Specific heat of copper  = 0.39 J g-1 K-1 ; heat of fusion of water = 335 J g-1 ).

A copper block of mass 2.5 k g is heated in a furnace to a temperature of 500 oC and then placed on a large ice block. What is the maximum amount of ice that can melt? (Specific heat of copper  = Read More …

## A 10 kW drilling machine is used to drill a bore in a small aluminium block of mass 8.0 kg. How much is the rise in temperature of the block in 2.5 minutes, assuming 50% of power is used up in heating the machine itself or lost to the surroundings. Specific heat of aluminium =09 1J g k-1 .

A 10 kW drilling machine is used to drill a bore in a small aluminium block of mass 8.0 kg. How much is the rise in temperature of the block in 2.5 minutes, assuming 50% of power is used up in heating Read More …

Page 1 of 3
1 2 3