Energy is emitted from a hole in an electric furnace at the rate of 20W when that temperature of the furnace is `727^@C`. What is the area of the hole (`sigma = 5.7 xx 10^-8 Js^-1m^-2K^-4`)

Energy is emitted from a hole in an electric furnace at the rate of 20 watt when furnace is at 227^@C . Find the area of the hole, sigma = 5.7 xx 10^-8 S.I . units.

A 60 watt filament lamp loses all its energy by radiation from its surface. The emissivity of the surface is 0.5. The area of the surface is 5 xx 10^-5m^3 . Find the temperature of the filament ( sigma = 5.67 xx 10^-8m^2s^-4K^-4 )

A 100 watt filament loses all its power by radiation, when it is heated to a temperature 2500 K. If the diameter of the filament is 0.2mm and emissivity of the filament is 0.5, find the length of the filament to ( sigma = 5.67 xx 10^-8 J//m^2sK^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.

Assuming that the sun radiates as a black body, calculate the energy radiated per minute by unit area of its surface. Surface temperature of the sun = 5727^@C and Stefan's constant = 5.7 xx10^-8 Jm^-2K^-4s^-1 .

Calculate the energy radiated is one minute by a blackbody of surface area 200 cm^2 at 127^@C ( sigma = 5.7 xx 10^-8 Jm^-2s^-1K^-4 )

A body having a surface area of 50cm^2 radiates 300J of energy per minute at a temperature of 727^(@)C . The emissivity of the body is ( Stefan's constant =5.67xx10^(-8)W//m^2K^4 )

What is the temperature at which a black body radiates heat at the rate of one kilowatt per unit area ? (Stefan 's constant sigma = 5.7 xx 10^(-8) S.Iunits)