light bulb pressure

[Fred_Also]

[quote billb]no vacumn

Halogens of course are filled with halogen gas.

Fluorescents are filled with fluorine gas?


Fred Also

[Craig]

I can't tell you the exact internal pressure, but the bulbs are left at a slight vacuum compared to atmospheric pressure. There are 2 reasons for this. As the bulb heats, the gas inside will expand according to the ideal gas law. When the gas is fully expanded the bulb will still be at a slight vacuum since if it breaks, you would want the glass shards to implode instead of explode.

If you wanted to estimate the pressure you would need to know P1V1T2 = P2V2T1

we know V1=V2 --> P1T2 = P2T1 --> P1 = (P2*T2)/T1 --> P1 = ATM * (T2/T1)
assume the gas is ideal
assume the pressure while the light is on is approximately atmospheric

Therefore you only need to know the operating temperature of the lit bulb to estimate the internal pressure of the bulb when it is un-lit.


Craig

[pbarra1]

That makes perfect sense Craig. And will explain the results of the demonstrations I saw today. Thanks.

[Mike V]

[quote lafinfil][quote Filliam H. Muffman] Hot glass shards spraying around a room could ruin your day.
True that !

I was photographing at an event and the videographer working next to me had a 250 watt quartz bulb blow.
It was in a Lowell Tote-a-Light and the idiot didn't have a safety cage on a bare bulb.

The hot glass shards started a small fire on the carpet and a chair.

Seen this happen so many times.

It's a pain to change the bubble when you have the screen fitted, but given enough use you will burn some flooring (or worse) eventually.