Take some water, say 300 ml, in a calorimeter with a stirrer and cover it with two holed lid
Fix a thermometer through a hole in the lid and make sure that the bulb of thermometer is immersed in the water. Note reading of the thermometer. This reading `T_(1)` is the temperature of the surrounding.
HEat the water kept in the calorimeter till it attains a temperature, say, `40" "^(@)C` above room temperature (i.e., temperature of the surroundings).
Then stop heating the water by removing the heat source.
Start the stopwatch and note the reading of the thermometer after fixed interval of time, say after every one minute of stirring gently with the stirrer.
Continue to note the temperature `(T_(2))` of water till it attains a temperature about `5" "^(@)C` above that of the surroundings.
Then plot graph by taking each value of temperature `DeltaT=T_(2)=T_(1)` along y axis and the corresponding value of t along x-axis.
From the graph you will infer how the cooling of hot water depends on the difference of its tempearture from that of the surroundings. You will also notice that initially the rate of cooling is higher and decreases as the temperature of the body falls.
The above activity shows that a hot body loses heat to its surroundings in the form of heat radiation.
The rate of loss of heat depends on the difference in temperature between the body and its surroundings.
