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A filament bulb that is heated to high temperature by passing electric current.The not filament emit black body radiation the filament is observed to break up due to evaporation of tungsten.If bulb is powered at constant voltage the which of the following is (are) true?

Option: 1

The resisitance over small section decrease with time


Option: 2

The filament emits more light at higher band of frequency before it breaks up.


Option: 3

The temperature distribution oer filament is uniform.


Option: 4

The filament consumes less electrical power towards end of life of bulb.


Answers (1)

best_answer

Because of evaporation, there is different cross section area as evaporation rate is higher cross section area reduces faster that breakup cross section area.
Resistance of whole wire increases with time and hence pover decreases.
At break area, temperature is higher and hence light of highest frepneng evils.

Posted by

Sanket Gandhi

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