The length of a brass rod is found to be smaller on a hot summer day that on a cold winter day as measured by the same aluminium scale. Do we conclude that brass shrinks on heating.

Read the following paragraph carefully and answer the following question . If the heat is exchanged between a hot and cold object,the temperature of the cold object goes on increasing due to gain of energy and the temperature of the hot object goes on decreasing due to loss of energy . The change in temperature continues till the tempertaures of both the object attain the same value . In the process, the cold object gains heat energy and the hot object lose heat energy . If the system of both the object is isolated form the environment by keeping it inside a heat resistance box ( meaning that the energy exchange takes place between the two object only), then no energy can flow from inside the box or come into the box. Which principle do we learn about from this process ?

On a cold winter day, the atmospheric temperature is -theta (on celsius scale) which is below 0^(@)C . A cylindrical drum of height h made of a bad conductor is completely filled with water at 0^(@)C and is kept outside without any lid. Calculate the time taken for the whole mass of water to freeze. Thermal conductivity of ice is K and its latent heat of fusion is L . Neglect expansion of water on freezing.

A meter scale is made up of steel and measures correct length at 16^@C . What will be the percentage error if this scale is used (a) on a summer day when the temperature is 46^@C .