An electric heater of surface area `200cm^2` emits radiant energy of 60 kJ at time interval of 1 min. Determine its emissive power. If its emissivity be 0.45, what would be the radiant energy emitted by a black body in one hour, identical to the electrical heater in all respects?

A body of surface area 10 cm^2 and temperature 727^@C emits 300 J of energy per minutes.Find the emissivity.

A body of surface area 10 cm^(2) and temperature 727 ^(@) C emits 600 J of enrgy per minute. Find its emissivity.

A metal cube has each side 2.5 cm long and radiates 0.36 kcal//min . What is the emissive power of its surface? If the emissivity of its surface is 0.4, what would be the emissive power of the cube if it were perfectly black?

The energy of 6000 J is radiated in 10 minutes by a body of surface area 200 cm^(2) . Find the emissive power of the body.

An electric heater ofpower 1kW emits thermal radiations the surface area of heating element of heater is 200 cm^(2) . If this heating element is treated like a black bodyfind the temperature at its surface. Assume its temperature is very much higher then its surroundings.

A body which has surface area of 5.0 cm^2 and a temperature of 727 radiates 300j of energy per minute.What is its emissivity?( sigma=5.67*10^-8 W/m^-2 K^-4 )

An electric heater whose power is 54 W is immersed in 650cm^3 water in a calorimeter. In 3 min the water is heated by 3.4^@C . What part of the energy of the heater passes out of the calorimeter in the form of radiant energy?

An electric heater whose power is 54 W is immersed in 650cm^3 water in a calorimeter. In 3 min the water is heated by 3.4^@C . What part of the energy of the heater passes out of the calorimeter in the form of radiant energy?

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.