In an earlier contribution to this discussion,
R D S wrote:

I use 6v bulbs, 15 Watt.

I struggle to get hold of them locally, could I use a 12v bulb? And
if so what wattage would be best?

My understanding of bulbs is that electricity passes through the
filament, it gets hot and glows, so there would surely be
interchangeability, is this about right?

Cheers,
Rick

At a very rough approximation, if you feed a 60w 12v bulb with 6v it will
consume about 15 watts.

However, this is pretty crude because the filament will not get as hot as
it's supposed to - and its resistance changes quite a lot with temperature -
so God knows what you'll *actually* get.

In any case, the chances of getting much useful light out of it are slim
because, at a lower temperature, most of the output will be in the form of
infra-red rather than visible light.
--
Cheers,
Roger
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