 |
Electric
current goes through the filament and heats it till its
white hot and it emits light |
|
When
something is hot, it means its atoms are moving a lot.
The filament’s atoms move so much, that they tear loose
from the other atoms and leave the surface of the metal
= Tungsten evaporates.
You’ve seen this happen elsewhere:
When you heat water , the water atoms move so quickly,
that they evaporate |
|
The
tungsten that has evaporated deposits itself on the "cool"
glass of the bulb |
|
The
tungsten leaving the filament, makes it thinner and more
fragile |
|
At
one point in time the filament is too thin and breaks
= End of lamp’s normal life |
