A calorimater is kept in a wooden box to insulate it thermally from the surroundings .Why is it neccessery?

A cylindrical rod of length 50cm and cross sectional area 1cm^(2) is fitted between a large ice chamber at 0^(@)C and an evacuated chamber maintained at 27^(@)C as shown in figure. Only small protions of the rod are insid ethe chamber and the rest is thermally insulated from the surrounding. The cross section going inti the evacuted chamber is blackened so that it completely absorbe any radiation falling on it. The temperatuere of the blackened end is 17^(@)C when steady state is reachhed. Stefan constant sigma=6xx10^(-s)Wm^(-2)K^(-4) . Find the thermal conductivity of the material of the rod.

A gas contained in a cylinder fitted with a frictionless piston expands against a constant external pressure or 1 atm from a volume of 5 litres to a volume of 10 litres. In doing so it absorbs 400 J of thermal energy from its surroundings. Determine the change in internal energy of system.

One end of a rod length 20cm is inserted in a furnace at 800K. The sides of the rod are covered with an insulating material and the other end emits radiation like a blackbody. The temperature of this end is 750K in the steady state. The temperature of the surrounding air is 300K. Assuming radiation to be the only important mode of energy transfer between the surrounding and the open end of the rod, find the thermal conductivity of the rod. Stefan constant sigma=6.0xx10^(-1)Wm^(-2)K^(-4) .

A person does 30 kJ work on 2 kg of water by stirring using a paddle wheel. While stirring, around 5 kcal of heat is released from water through its container to the surface and surroundings by thermal conduction and radiation. What is the change in internal energy of the system?

In a Van de Graaff type generator, a spherical metal shell is to be a 15 xx 10^6V electrode. The dielectric strength of the gas surrounding the electrode is 5 xx 10^7 Vm^(-1) . What is the minimum radius of the spherical shell required? (You will learn from this exercise why one cannot build an electrostatic generator using a very small shell which requires a small charge to acquire a high potential.)