Calculate the amount of heat radiated per second by a body of surface area `12 cm^2` kept in thermal equilibrium in a room at temperature `20°C`. The emissivity of the surface `=` `0.80` and `sigma = 6.0 × 10^-8 W m^-2 K^-4`

Calculate the amount of heat radiated per second by a body of surface area 12cm^(2) kept in thermal equilibrium in a room at temperature 20^(@)C The emissivity of the surface =0.80 and sigma=6.0xx10^(-s)Wm^(-2)K^(-4) .

How much energy is radiated per minute from the filament of an incandescent lamp at 3000 K , if the surface area is 10^-4 m^2 and it's emissivity is 0.4 ? Stefan's constant sigma = 5.67 × 10^-8 W m^-2 K^-4

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

A blackbody of surface 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.

Assume that the total surface area of a human body is 1.6m^(2) and that it radiates like an ideal radiator. Calculate the amount of energy radiates per second by the body if the body temperature is 37^(@)C . Stefan constant sigma is 6.0xx10^(-8)Wm^(-2)K^(-4) .

An electric heater emits 1000W of thermal radiation. The coil has a surface area of 0.02m^(2) . Assuming that the coil radiates like a blackbody, Find its temperature. sigma=6.0xx10^(-8)Wm^(-2)K^(-2) .

Calculate the saturation thermionic current if 120 W is applied to a thoriated-tungsten filament of surface area 1.0 cm^2 . Assume that the surface radiates like a blackbody. The required constants are A = 3 xx10^4 A m^(-2) -K^2 , varphi = 2.6 eV, k = 8.62 xx 10^(-5) eV kK^(-1) and sigma = 6 xx 10^(-8) W m^(-2) K^(-4)

The operating temperature of a tungsten filament in an incandescent lamp is 2000 K and it's emissivity is 0.3 . Find the surface area of the filament of a 25 watt lamp. Stefan's constant sigma = 5.67 × 10^-8 W m^-2 K^-4

A spherical ball of surface area 20cm^(2) absorbs any radiation that falls on it. It is suspended in a closed box maintained at 57^(@)C . (a) Find the amount of radiation falling on the ball per second. (b) Find the net rate of heat flow to or from the ball at an instant when its temperature is 200^(@)C . Stefan constant =6.0xx10^(-s)Wm^(-2)K^(-4) .

The saturation current from a thoriated-tungsten cathode at 2000 K is 100 mA . What will be the saturation current for a pure-tungsten cathode of the same surface area operating at the same temperature? The constant A in the Richardson-Dushman equation is 60 xx 10^4 A m^(-2) K^(-2) for pure tungsten and 3.0 xx 10^(4) A m^(-2) K^(-2) for thoriated tungsten. The work function of pure tungsten is 4.5 eV and that of thoriated tungsten is 2.6 eV .