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`

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

The wavelength of maximum intensity of radiation emitted by a star is 289.8nm. The radiation intensity for the star is (Stefan's constant = 5.67×10^-8Wm^-2K^-4 , constant b = 2898mumK ).

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

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) .

A spherical tungsten pieces of radius 1.0cm is suspended in an evacuated chamber maintained at 300K . The pieces is maintained at 1000K by heating it electrically. Find the rate at which the electrical energy must be supplied. The emissivity of tungsten is 0.30 and the Stefan constant sigma is 6.0xx10^(-s)Wm^(-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 constant A in the Richardson-Dushman equation for tungsten is 60 xx 10^(4) A m^(-2) . The work function of tungsten is 4.5 eV . A tungsten cathode having a surface area 2.0 xx 10^(-5) m^2 is heated by a 24 W electric heater. In steady state, the heat radiated by the cathode equals the energy input by the heater and the temperature becomes constant. Assuming that the cathode radiates like a blackbody, calculate the saturation current due to thermions. Take Stefan constant = 6 xx 10^(-8) W m^(-2) K^(-4) . Assume that the thermions take only a small fraction of the heat supplied.

One end of a rod length 20cm is inserted in a furnace at 800K. The sides of the rod are covered with an insulating material and the other end emits radiation like a blackbody. The temperature of this end is 750K in the steady state. The temperature of the surrounding air is 300K. Assuming radiation to be the only important mode of energy transfer between the surrounding and the open end of the rod, find the thermal conductivity of the rod. Stefan constant sigma=6.0xx10^(-1)Wm^(-2)K^(-4) .

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)

A satellite orbits the earth at a height of 400 km above the surface. How much energy must be expended to rocket the satellite out of the earth’s gravitational influence? Mass of the satellite = 200 kg, mass of the earth = 6.0 ×x 10^(24) kg, radius of the earth = 6.4 xx 10^(6) m , G = 6.67 xx 10^(-11) N m^(2)) kg^(-2) .