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Old 18th Apr 2021, 11:39 pm   #9
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 4,451
Default Re: Crompton 60W bulb

I don't have any vacuum lamps to try myself, but an old school physics book describes an experiment with two bulbs of the same wattage, one vacuum and one gas-filled, where the glass of the vacuum lamp was said to remain cold to the touch in operation. It was said that, for the vacuum bulb, radiant heat would pass through glass without appreciable absorbtion, whereas the gas-filled bulb's glass would get heated by convection. I believe this was why bare vacuum bulbs could be used outdoors without their glass being damaged by falling rain.

Last edited by emeritus; 18th Apr 2021 at 11:40 pm. Reason: typo
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