A metal sphere with a black surface and radius `30 min`, is cooled to `-73C (200K)` and placed inside an enclosure at a temperature of `27^(@)C(300K)`. Calculate the initial rate of temperature rise of the sphere, assuming the sphere is a black body. (Assume density of metal `=8000 kg m^(-3)` specific heat capacity of metal `=400 J kg^(-1)K^(-1)`, and Stefan constant `=5.7xx10^(-8)Wm^(-2)K^(-4)`).

A copper cube with sides o flength 20 mm had its surface blackened. The cube is heated up to 500K and placed inside a room at a constant temperature of 300K. Calculate the initial rate of temperature fall of the cube, assuming it as a perfect black-body. (Stefan's constant = 5.7 xx 10^(-8) W//m(2) //K^(4) specific heat capacity of aluminium = 400 J //kg//K , density of aluminium = 7800 kg//m^(3) ) where A is the surface area of the cube, T_(1) is the temperature of the body, and T_(2) is the temperature of the enclosure.

A solid copper sphere of dimater 10mm is cooled to temperature of 150K and is then placed in an enclousure at 290K Assuming that all interchange of heat is by radiation, calculate the initial rate of rise of temperature of the sphere The sphere may be treated as a black body rho_(copper) =8.93xx 10^(3)kg//m^(3) s = 3.7xx10^(2) Jkg^(-2) K^(-1) , sigma = 5.7 xx 10^(8) Wm^(-2) K^(-4) .

A solid copper sphere of dimater 10mm is cooled to temperature of 150K and is then placed in an enclousure at 290K Assuming that all interchange of heat is by radiation, calculate the initial rate of rise of temperature of the sphere The sphere may be treated as a black body rho_(copper) =8.93xx 10^(3)kg//m^(3) s = 3.7xx10^(2) Jkg^(-2) K^(-1) , sigma = 5.7 xx 10^(8) Wm^(-2) K^(-4) .

A black body of mass .0.10 g is kept in a black enclosure or temperature 27^(@) C. The temperature of the body is 127^(@) C and the area of the emittimg surface in 10^(-3) m^(2) . If its specific heat capacity is 420 J kg^(-1)k^(-1) find the rate of cooling of the body . sigma = 5.67xx10^(-8)Wm^(-2)K^(-4) .

A black body of mass 34.38 g and surface area 19.2cm^(2) is at an intial temperature of 400 K. It is allowed to cool inside an evacuated enclosure kept at constant temperature 300 K. The rate of cooling is 0.04^(@)C//s . The sepcific heat of the body J kg^(-1)K^(-1) is (Stefan's constant, sigma = 5.73 xx 10^(-8)Wm^(-2)K^(-4))

A black body of mass 34.38 g and surface area 19.2cm^(2) is at an intial temperature of 400 K. It is allowed to cool inside an evacuated enclosure kept at constant temperature 300 K. The rate of cooling is 0.04^(@)C//s . The sepcific heat of the body J kg^(-1)K^(-1) is (Stefan's constant, sigma = 5.73 xx 10^(-8)Wm^(-2)K^(-4))

If the sun's surface radiates heat at 6.3 xx 10^(7) Wm^(-2) . Calculate the temperature of the sun assuming it to be a black body (sigma = 5.7 xx 10^(-8)Wm^(-2)K^(-4))

A solid metallic sphere of diameter 20 cm and mass 10 kg is heated to a temperature of 327^@C and suspended in a box in which a constant temperature of 27^@C is maintained. Find the rate at which the temperature of the Sphere will fall with time. Stefan's constant =5.67xx10^-8W//m^(2)//K^(4) and specific heat of metal =420J//kg//^(@)C .

A solid metallic sphere of diameter 20 cm and mass 10 kg is heated to a temperature of 327^@C and suspended in a box in which a constant temperature of 27^@C is maintained. Find the rate at which the temperature of the Sphere will fall with time. Stefan's constant =5.67xx10^-8W//m^(2)//K^(4) and specific heat of metal =420J//kg//^(@)C .

A black body with surface area 0.001 m^2 is heated upto a temperature 400 K and is suspended in a room temperature 300 K. The initial rate of loss of heat from the body to room is