A copper sphere is suspended in an evacuated chamber maintained at `300K`. The sphere is maintained at a constant temperature of `500K` by heating it electrically. A total of `210W` of electric power is needed to do it. When the surface of the copper sphere is completely blackened, `700W` is needed to maintain the same temperature of the sphere. Calculate the emissivity of copper.

A copper sphere is suspended in an evacuated chamber maintained at 300 k. The sphere is maintained at a constant temperature of 500 K by heating it electrically. A total of 210 W of electric power is needed to do it. When the surface of the copper shphere is completely blackened, 700 W is needed to maintain the same temperature of the sphere. Calculate the emissivity of copper.

A copper sphere is suspended in an evacuated chamber maintained at 300K. The sphere is maitained at a constant temperature of 500K by heating it electrically. A total of 210W is electric power is needed to do it. When the surface of the copper sphere is completely blackned, 700W is needed to maintain the same temperature of the sphere. Calculate the emissivity of copper.

A copper sphere is suspended in an evacuated chamber maintained at 300 K . The sphere is mantained at a constant temperature of 500 K by heating it electrically. A total of 300 W of electric power is needed to do it. When half of the surface of the copper sphere is completely blackened, 600W is needed to maintain the same temperature of the the sphere. Calculate the emissivity of copper.

A copper sphere is maintained at 500 K temperature by connecting it to a battery of emf V_(1) = 100 V (see figure). The surrounding temperature is 300 K. When half the surface of the copper sphere is completely blackened (so that the surface behaves almost like a black body), a cell of emf V_(2) = 141 V is needed to maintain its temperature at 500 K. Calculate the emissivity of the copper surface.

A spherical tungsten pices of radius 1.0cm is suspended in an evacuated chamber maintained at 300K. The pices is maintained at 1000K by heating it electrically. Find the rate at which the electrical energy must be supplied. The emissivity of tungsten is 0.30 and the Stefan constant sigma is 6.0xx10^(-s)Wm^(-2)K^(-4) .

A spherical tungsten piece of radius (1)/(sqrt(pi)) cm is suspended in an evacuated chamber maintained at 200 K . The piece is maintained at 400 K by heating it electrically. Find the rate at which the electrial energy must be supplied. The emissivity of tungsten is 0.50 , the Steafan constant sigma is 6.0 xx 10^(-8) W//m^(2)-K^(4)

A blackbody of surface area 1cm^(2) is placed inside an enclosure. The enclosure has a constant temperature 27(@)C and the blackbody is maintained at 327(@)C by heating it electrically. What electric power is needed to maintain the temperature? sigma=6.0xx10^(-s)Wm^(-2)K(-2) .

A solid cube and a sphere are made of the same material and both have the same surface area. If both are at the temperature of 300 K then initial

Two copper spheres of radii 6 cm and 12 cm respectively are suspended in an evacuated. Each of them is at a temperature 15^(@)C above the surroundings. The ratio of their of loss of heat is

Two sphere of same radius and material, one solid and one hollow are heated to same temperature and kept in a chamber maintained at lower temperature at t = 0 -