Stefan's law of radiation, also known as the Stefan-Boltzmann law, states that the total energy radiated per unit surface area of a black body per unit time (also known as the radiant heat power) is directly proportional to the fourth power of the black body's absolute temperature (T).
Mathematically, it is expressed as:
Eb=σ×T4
where Eb is the emissive power of a blackbody,
T is absolute temperature, and σ =5.67×10-8)
A lamp takes 5A at 250 V and emits 4000 lumens. Its MSCP is:
Which of the following effect is responsible for the production of light in an electric discharge lamp?
According to lambert's cosine law, the illumination at any point on a surface illuminated by a source of light, with light rays inclined at an angle θ to the normal at that point, varies as:
Which of the following statements are correct about the maintenance factor?
I) It is the ratio of illumination under normal working condition to the total lumen given out by the lamp.
II) It is the ratio of illumination under normal working condition to the illumination when the things are perfectly clean.
III) The accumulation of dust, dirt and smoke on the lamp decreases the maintenance factor.
IV) It is the ratio of illumination when the things are perfectly clean to the illumination under normal working condition.
The scattering of molten metal droplets outside the weld zone, which can lead to surface irregularities is called weld__________.
In regard to installations of street lighting, what is the average illumination level of Class A1 installations used in important shopping centres and at road junctions?
A lamp takes 5A at 250 V and emits 4000 lumens. Its MSCP is:
