An incandesecent bulb has a thin filament of tungstgen that is heated to high temperature by
passing an electric current. The hot filament emits black - body radiation. The filament is
observed to break up at random location after a sufficiently long time of operation due to
non - uniform evaporation of tungsten from the filament. If the bulb is powered at constant
voltage, Which of the following statement(s) is(are) true?
Select ALL correct options:
A
The temperature distribution over the filament is uniform
B
The resistance over small sections of the filament decreases with time
C
The filament emits more light at higher band of frequencies before it breaks up
D
The filament consumes less electrical power towards the ends of the life of the bulb
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
⚠ Partially correct. Some answers are missing.
Solution
As the temperature increases, $\lambda_{\mathrm{m}}$m
decreases. So frequency of radiation increases with increase in
temperature and resistance increases. So current decreases and hence power consumed (P = Vi)
decreases (V is constant given)
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