On Fri, 4 Jul 2008 01:23:49 +0100 "Arfa Daily"
wrote:
I have noticed that these new smaller bulbs run a whole quantum leap hotter
than the older larger size, and they hot up the shade on the bench light
until it is unbearably hot to touch.
Lost in this conversation is the fact that you claim that both the old
and new bulbs have been 60 Watts. Now, if that's true, then there's no
more power available from the new 60 W lamps than there was from the
old 60 W lamps.
Halogen lamps, while they DO have much hotter envelopes, convert
electrical power into visible lighte somewhat more efficiently, so
that should make the shade run slightly cooler, if anything. I would
expect this effect to be small.
Certainly a smaller 60 W bulb will run at a higher glass envelope
temperature, but that envelope will be farther from the shade,
assuming that they both got mounted on the same centers. The end
result is that there will be no difference in the radiant heating of
the shade.
The confusion here seems to be the common one between temperature and
heat. Cram the same amount of heat into a smaller amount of material
and you'll get a higher temperature, but in this case, the shade has
remained the same, so the amount of heat energy collected should be
the same, and the resulting temperature should also be the same.
It may help to think of heat and temperature as having electrical
analogs in charge and voltage.
Really, there are only 2 possible conclusions: Either the new bulb is
actually higher wattage than the old one, or the perception of a
hotter shade is mistaken.
Separate from this is heat conduction thru the base of the bulb. If
the bulb is shorter and hotter, then it will likely conduct more heat
into the socket. Halogen sockets are generally ceramic or some rather
special high temp plastic in order to deal with this, so putting a
halogen bulb in a standard socket will always result in a destroyed
socket.
-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------