A hollow cube `A` of very small thickness at temperature `T` emits radiation like a black body. The cube `A` is kept in a room of temperatue `T_(0)(ltT)`. The side of cube is doubled without changing the volume of material and its temperature. Find the ratio of rate of cooling of cube `A` in first case to that of second case.

A sphere and a cube of same material and same total surface area are placed in the same evaculated space turn by turn after they are heated to the same temperature. Find the ratio of their initial rates of cooling in the enclosure.

A sphere and a cube of same material and same total surface area are placed in the same evaculated space turn by turn after they are heated to the same temperature. Find the ratio of their initial rates of cooling in the enclosure.

A sphere and a cube of same material and same total surface area are placed in the same evaculated space turn by turn after they are heated to the same temperature. Find the ratio of their initial rates of cooling in the enclosure.

A and B are two sphere made of same material. Radius of A is double that of B and initially they are at same temperature (T). Both of them are kept far apart in a room at temperature T_(0)(lt T) . Calculate the ratio of initial rate of cooling (i.e. rate of fall of temperature) of sphere A and B if (a) the spheres are solid, (b) the spheres are hollow made of thin sheets of same thickness

There are two thin spheres A and B of the same material and same thickness. They behave like black bodies, Radius of A is double that of B and Both have same temperature T. When A and B are kept in a room of temperature T_0 (lt T) , the ratio of their rates of cooling is (assume negligible heat exchange between A and B).

There are two thin spheres A and B of the same material and same thickness. They behave like black bodies, Radius of A is double that of B and Both have same temperature T. When A and B are kept in a room of temperature T_0 (lt T) , the ratio of their rates of cooling is (assume negligible heat exchange between A and B).

There are two thin spheres A and B of the same material and same thickness. They behave like black bodies, Radius of A is double that of B and Both have same temperature T. When A and B are kept in a room of temperature T_0 (lt T) , the ratio of their rates of cooling is (assume negligible heat exchange between A and B).

One end of a rod of 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 black body. 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's constant sigma = 6.0 xx 10^(-8) W m^(-2) K^(-4) .

A spherical body of area A, and emissivity e = 0.6 is kept inside a black body. What is the rate at which energy is radiated per second at temperature T