Home
Class 11
PHYSICS
A blackbody of sarface area 10cm^(2) is...

A blackbody of sarface area `10cm^(2)` is heated to `127^(@)C` and is suspended in a room at temperature `27^(@)C` calculate the initial rate of loss of heat from the body to the room.

Text Solution

Verified by Experts

For a blackbody at temperature T, the rate of emission is `u=sigmaAT^(4)` . When it is kept in a room at temperature `T_(0)`, the rate of absorption is `u_(0)=sigmaA(T^(4)-(t^(4)0)` .Here `A=10xx10^(4)m^(2)` , `T=400K` and `T_(0)=300K` . Thus, `u-u_(0)`
`=(5.67xx10^(-8)Wm^(-2)K^(-4)(10xx10^(-4)m^(2))(400^(4)-(300^(4))K^(4)`
`=0.99W`.
Promotional Banner

Similar Questions

Explore conceptually related problems

Area of surface of a person is "1.9 m"^(2) and its body temp. is 37^(@)C and room temp. is 22^(@)C . Temperature of skin is 28^(@)C , then find the rate of emission of heat. Emissivity of skin is 0.97 .

A metallic sphere having radius 0.08 m and mass m = 10 kg is heated to a temperature of 227^(@)C and suspended inside a box whose walls ae at a temperature of 27^(@)C . The maximum rate at which its temperature will fall is:- (Take e =1 , Stefan's constant sigma = 5.8 xx 10^(-8) W//m^(-2)K^(-4) and specific heat of the metal s = 90 cal//kg//deg J = 4.2 "Joules"//"Calorie")

In an experiment on the specific heat of a metal, a 0.20 kg block of the metal at 150^(@) C is dropped in a copper calorimeter (of water equivalent 0.025 kg containing 150 cm^(3) of water at 27^(@)C . The final temperature is 40^(@) C . Compute the specific heat of the metal. If heat losses to the surroundings are not negligible. Is your answer greater or smaller than the actual value for specife heat of the metal ?

A refrigerator is to maintain eatables kept inside at 9^(@)C . If room temperature is 36^(@)C , calculate the coefficient of performance.

In an experiment on the specific heat of a metal, a 0.20 kg block of the metal at 150^(@)C is dropped in a copper calorimeter (of water equivalent 0.025 kg) containing 150" cm"^(3) of water at 27^(@)C . The final temperature is 40^(@)C . Compute the specific heat of the metal. If heat losses to the surroundings are not negligible, is your answer greater or smaller than the actual value for specific heat of the metal ?

A carbot freezer takes heat from water at 0^(@)C inside it and rejects it to the room at a temperature of 27^(@)C . The latent heat of ice is 336xx10^(3)Jkg^(-1) . If 5kg of water at 0^(@)C is converted into ice at 0^(@)C by the freezer, then the energy consumed by the freezer is close to :

A refrigerator is to maintain eatables kept inside at 9^@ C. If room temperature is 36^@ C , calculate the coefficient of performance of refrigerator.

A refrigerator is to maintain eatables kept inside at 9^@ C. If room temperature is 36^@C , calculate the coefficient of performance.

An electric heater is used in a room of total wall area 137m^(2) to maintain a temperature of +20^(@)C inside it when the outside temperature is -10^(@)C . The walls have three different layers materials . The innermost layer is of wood of thickness 2.5 cm, in the middle layer is od cement of thickness 1.0 cm and the outermost layer is of brick of thickness 25.0 cm. find the power of the electric heater. Assume that there is no heat loss through the floor and the ceiling. The thermal conductives of wood, cement and brick are 0.125, 1.5 and 1.0 watt//m// .^(@)C respectively.