Since the filament of an incandescent light bulb gets as hot as it
does, the thermal coefficient of the tungsten is a factor to be considered.
If you figure out what the resistance of a 100 Watt bulb must be to draw
the correct current for your local mains power and then read a cold bulb
with your Ohm meter, you will see that the resistance is very low and nowhere
close to what your calculation said it should be.  This means that the
resistance of the bulb will drop as it dims which will increase the current
over what one would expect with a fixed resistor of some kind.  This also
means that there is a serge of current when power is applied and
the filament is not yet hot.  This is why switching circuits for
incandescent lamps are rated for higher amperages than if those same switches
are used for other types of loads.  The bulb can act as a sort of poor man's
constant current source if one isn't too picky about accuracy.

Martin McCormick WB5AGZ  Stillwater, OK 36.7N97.4W
OSU Center for Computing and Information Services Data Communications Group