A blackened solid copper sphere of radius 2 cm is placed in an evacuated enclosure whose walls are kept at `100^(@)C`. At what rate must energy be supplied to the sphere to keep its temperature constant at `127^(@)C` ? Stefan constant `= 5.67xx 10^(-8)Jm^(-2)K^(-4).`

A black ened metal sphere of radius 7 cm is encllosed in as evacuated chamber maintained at a temperature of 27^(@)C . At what rate must energy be supplied to the sphere so as to keep its temperature constant at 127^(@)C ? sigma=5.7xx10^(-8) W m^(-2) K^(-4) .

A small blackened solid copper sphere of radius 2.5cm is placed in an evaculated chamber. The temperature of the chamber is maintained at 100^@C . At what rate energy must be supplied to the copper sphere to maintain its temperature at 110^@C . ( sigma = 5.76 xx 10^-8 Js^-1m^-2K^-4 ) Treat sphere as black body.

Calculate the energy radiated in 30 seconds by perfectly black sphere of radius5cm maintained at 127^@C . (Stefan's constant s = 5.7 xx 10^-8 J//m^2sk^4)

The emissivity of tungsten is approximately 0.35. A tungsten sphere 1 cm in radius is suspended within a large evacuated inclosure whose walls are at 300K. What power input is required to maintain the sphere at a temperature of 3000K? (sigma=5.67xx10^(-8)" in SI unit")

The emissivity of tungsten is 0.4. A tungsten sphere with a radius of 4.0 cm is suspended within a large evacuated enclosure whose walls are at 300 K. What power input is required to maintain the sphere at a temperature of 3000 K if heat conduction along supports is neglected ? Take, sigma = 5.67 xx (10^-8) Wm^2-K^4 .

The emissivity of tungsten is 0.4. A tungsten sphere with a radius of 4.0 cm is suspended within a large evacuated enclosure whose walls are at 300 K. What power input is required to maintain the sphere at a temperature of 3000 K if heat conduction along supports is neglected ? Take, sigma = 5.67 xx (10^-8) Wm^2-K^4 .