"Is it really valid to assume the current in a light globe is the same
for
50Hz as 100kHz? I would suspect that the "coiled coil" tungsten
filament
may alter this. It might be interesting to compare this to another
method
of current readings such as with a high speed bridge rectifier feeding a
capacitor and a DC ammeter.
Peter"
Almost certainly, because the Q of the filament is so low that the
reactance probably doesn't count below 1 MHz or so. There are tubes
specifically made for power measurement which consist of two identical
straight filaments mounted in an evacuated envelope. The power to be
measured is fed to one filament and the current in the other adjusted
from a separate source to give equal brightness (the eye is very
sensitive to small brightness differences), at which point the two
powers can be considered equal. I've used a similar method to measure
powers at frequencies as high as 1200 MHz and the accuracy, compared to
a VHF wattmeter, seemed to be within 10% or better.
Ed