Apoorva Arora
Last Activity: 10 Years ago
When it is switched on, its resistance is less than a tenth of its usual working level so an initial current more than 10 times the rated value surges into the filament, heating it very rapidly and creating thermal stress.
If any part of that filament is slightly thinner than the rest, this area will heat up more quickly. Its resistance per millimetre will be higher than that of the rest of the filament, so more heat will be generated along this stretch than in the adjacent parts of the filament, amplifying the thermal stress.
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Apoorva Arora
IIT Roorkee
askIITians Faculty