"John Rumm" wrote in message
et...
Richard Head wrote:

"BigWallop" wrote in message
om...
"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my
kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.



********

Ah, a charm school graduate I see...

I expect by "colour value" BW probably meant CRI, which is indeed higher
for a 12V halogen, and the light is certainly whiter. Many 12V lamps also
have dichroic reflectors that also enhances the whiteness of the light by
allowing some of the redder end of the spectra to escape out of the back
of the bulb...

So I don't think you can really say "********" unless it was of course a
prelude to what you were about to follow it with.

Its all to do with the filament size. On a 12V lamp the filament guage is
much lower and the filament winding diameter is larger, and there are
fewer turns so:-

1) More exposed surface area so more light can escape from the confines
of the filament and

Not that convincing really, also missing the more relevant point that the
more robust filament can be run at a higher temperature which yields the
aforementioned whiter light, and an increase in efficiency (i.e. more
lumens per watt) which is why it not only appears brighter for the same
power consumption, but in reality *is* brighter.

2) A 12V filament is far more robust and will last longer

true, but not relevant to the question

--
Cheers,

John.

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Thankyou for the replies, I didn't think the dichrioc reflector had much to
do with it as both lamps have them but when you look at the capsual the 12v
one is a lot brighter. I just done a bit of quick maths and the 12v 50w lamp
draws 4.16 amps and the 240v 50w lamp draws 0.208 amps so I gather more amps
= more light.