Lighting effect of electricity is used in incandescent lamp a) What is the meaning of the word “incandescent” b) The bulb is evacuated. Why? c) Which gas is filled inside the bulb? Why?
Answers
When electric current flows through the conductor of high resistance, first it becomes very hot and then glows to emit light. Electric bulbs such as filament lamp (also called incandescent lamp) and fluorescent lamp are the important application of lighting effect of electric current.
a)emitting light as a result of being heated.
b)An electric bulb, particularly the incandescent bulb, is evacuated to prevent the reaction of air with the tungsten filament in the bulb which would appreciably shorten its lifespan. If the filament were exposed to air, there would be rapid oxidation of the filament.
c)The main reason that bulbs are filled with an inert gas is to reduce evaporation of the filament and prevent its oxidation. The most popularly used filling in electric bulbs is a mixture of Argon and Nitrogen. However, due to the lesser amount of Nitrogen (around 7 %), it is known as Argon fills.
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