What are the dimensions of Stefan’s constant?
The energy emitted per unit area per second by a black body is given by
Where is the Stefan’s constant and T is the absolute temperature.
Two rods A and B of different materials are welded together as shown in Fig. If their thermal conductivities are k1 and k2 , the thermal conductivity of the composite rod will be
A one liter flask contains some mercury. It is found that at different temperatures the volume of air inside the flask remains the same. What is the volume of mercury in the flask? Given the coefficient of linear expansion of glass oC–1, the coefficient of volume expansion of mercury is oC–1.
A wire of cross-sectional area A at temperature t is held taut with negligible tension between two rigid supports. If the wire is cooled to a temperature what tension is developed in the wire? The coefficient of linear expansion is and the Young’s modulus of the wire is Y.
Two uniform brass rods A and B of length l and 2l and radii 2r and rrespectively are heated to the same temperature. The ratio of the increase in the length of A to that of B is
Two rods of different materials having coefficients of thermal expansion and Young’s modulii Y1, Y2 respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There is no bending of the rods. If the thermal stresses developed in the two rods are equal provided Y1 : Y2 is equal to:
The water equivalent of a copper calorimeter is 4.5 g. If the specific heat of copper is 0.09 cal.g–1oC–1 the
A slab of stone of area 0.34 m2 and thickness 10 cm is exposed on the lower face to steam at 100oC. A block of ice at 0oC rests on the upper face of the slab. In one hour, 3.6 kg of ice is melted. Assume that the heat loss from the sides is negligible. The latent heat of fusion of ice is What is the thermal conductivity of the stone in units of Js–1m–1oC–1?
An ice-box is made of wood 1.75 cm thick, lined inside with cork 2 cm thick. If the temperature of the inner surface of the cork is steady at 0oC and that of the outer surface is steady at 12oC, what is the temperature of the surface? The thermal conductivity of wood is 5 times that of cork.
The tungsten filament of an electric lamp has a surface area A and a power rating P. if the emissivity of the filament is is Stefan’s constant, the steady temperature of the filament will be
Each square meter of sun’s surface radiates energy at the rate of . Assuming that Stefan’s law applies to the radiation, the temperature of sun’s surface is (Stefan’s constant )