Why did a 240V 500W bulb stop burning in a 230V 300W lamp?

  • Level: Undergrad 
  • Thread starter Thread starter fawk3s
  • Start date Start date
  • Tags Tags
    Lightbulb
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
1 reply · 2K views
fawk3s
Messages
341
Reaction score
1
I recently ran into the situation where one of my lamps lightbulb burned out. So I changed the bulb. I left home for a second and when I came back, the bulb wasnt burning anymore. So I started to investigate it.
Turns out the new bulb didnt burn out. Everything seems to be ok with it, but then I noticed the sign on the bulb which said "240V; 500W". So I immediately checked the lamps aswell. That one said "MAX: 230V; 300W".
Calculating by the formula N=UI, we get that the maximum current for the lamp/the old bulb could be approximately 1,3A. For the new bulb it could be about 2,1A.

I haven't bought a new bulb for the lamp yet, but I am interested what actually happened there.
What happened that caused the bulb not to burn anymore, even though it burned at first?
Did the bulb "demand" too much out of the lamp and damaged it somehow?
Or did something happen to the bulb?

I haven't tried the lamp with a new bulb, and I have examined the bulb carefully. It seems to be fine looking outside.

Thanks in advance,
fawk3s
 
Physics news on Phys.org
The lamp socket could have failed from oxidation or overheating. Contact springs will relax when overheated. Some light fixtures have a "thermal fuse". Different types will temporarily or permanently open if the fixture overheats.

Failure of the fixture was probably not the current directly. Tungsten lamps will draw many times their operating current when voltage is first applied.