JEE Advanced 2016 Physics question
An incandescent bulb has a thin filament of tungsten 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 locations 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?
Solution
Non-uniform evaporation makes some sections thinner than others. A thinner section has larger resistance per unit length () and, carrying the same current, dissipates more power in less material, so it becomes hotter: the temperature is not uniform (A false) and the resistance of small sections
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