I am working out the wattage of some of my spare 118mm linear halogen bulbs. I have access to only a regular meter.
So I have measured the resistence of the bulb when cold.
(Q1) Is the resistence likely to change significantly from my cold reading compared to when the bulb is at operating temperature? Is there a rule-of-thumb multiplier for such bulbs.
(Q2) Is the filament material used likely to vary from manufacturer to manufacturer in a way that noticeably affects the relationship between the cold resistence and hot resistence of a bulb? (If you see what I mean.)
FWIW I am in the UK with 230 volt mains and my cold resistence readings are 12.1 ohms, 13.5 ohms, and 8.1 ohms. Presumably the first two are 300W bulbs and the third is 500W.