In article ,
"Trevor Smith" writes:
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?

"Brighter" could mean many things (gives off more light,
illuminates the target object better, illuminates the room
better, has a higher intensity beam centre, etc). You
weren't specific.

A 12V filament lamp of that power is significantly more efficient
than a 240V filament of that power. If you want to design the
most efficient filament to operate at 100W, it turns out to be
one designed to run on about 55V. (It's not going to be very
different for 50W.) 12V is nearer to this peak efficiency than
240V. That's also the reason a US 100W 120V lamp gives off more
light than a UK 100W 240V lamp.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]