What does the kelvin (K) mean??

Submitted: Thursday, Feb 07, 2008 at 12:50
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To purchase a 12v compact fluoro globe for my camp light. Choice of 3000k or 5000k. Whats the difference?? What does the K indicate??
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Reply By: Robin Miller - Thursday, Feb 07, 2008 at 13:03

Thursday, Feb 07, 2008 at 13:03
Temperature above absolute zero - ice freezes at 273 degrees kelvin.

5000 kelvin means light is whiter than 3000 kelvin which is
also called warm white and is slightly yellow.
Robin Miller

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Follow Up By: Hopper51 - Thursday, Feb 07, 2008 at 13:09

Thursday, Feb 07, 2008 at 13:09
Ice doesn't freeze. Water freezes and that occurs at 273 degrees kelvin or 0 degrees centigrade.
Chris W
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Follow Up By: robak (QLD) - Thursday, Feb 07, 2008 at 14:29

Thursday, Feb 07, 2008 at 14:29
since we're being picky - I think the term is Celcius not centigrade.
;)

R
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Follow Up By: Hopper51 - Thursday, Feb 07, 2008 at 14:40

Thursday, Feb 07, 2008 at 14:40
Both units are correct. It depends when and where you went to school.
Chris W
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Follow Up By: Spider - Thursday, Feb 07, 2008 at 14:44

Thursday, Feb 07, 2008 at 14:44
Since we are being really picky now :

Used to be called Centigrade

Now called Celsius, not Celcius.

The bloke who invented the Celsius scale actually had the scale reveresed to what it is now. If left alone, water would boil at 0 degrees and water would freeze at 100 degrees. That would be quite confusing, particularly comparing with Kelvins or Farenheit.

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Follow Up By: robak (QLD) - Thursday, Feb 07, 2008 at 14:49

Thursday, Feb 07, 2008 at 14:49
well, there you go.
Learn a new thing everyday.
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Follow Up By: Member -Signman - Thursday, Feb 07, 2008 at 15:30

Thursday, Feb 07, 2008 at 15:30
Geez- I just need enough light to boil the billy...
Whether it's celcius/centigrade/ or whatever...but (seriously) what does temperature got to do with light output/colour ???
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Follow Up By: robak (QLD) - Thursday, Feb 07, 2008 at 15:34

Thursday, Feb 07, 2008 at 15:34
If you were to heat a piece of metal, the hotter it got the whiter its colour would be. The cooler it became the reder the colour.
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Follow Up By: Member -Signman - Thursday, Feb 07, 2008 at 15:43

Thursday, Feb 07, 2008 at 15:43
Thanks robak
That makes sense- kind of ....
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Follow Up By: Member No 1- Thursday, Feb 07, 2008 at 15:54

Thursday, Feb 07, 2008 at 15:54
its minus 273C (might be a decimal point in there but i rounded off if there is) = absolute zero...the theoretical temperature where no heat is available...me thinks the south/north poles in a blizzard or on a cold day must be like queensland when compared to -273
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Reply By: equinox - Thursday, Feb 07, 2008 at 13:05

Thursday, Feb 07, 2008 at 13:05
Kelvin is the numbers of degrees above absolute zero. (minus 273 degress celcius)

In regards to lamps it means the equivalent colour temperature.

Warm White - 2700k to 3000k
Cool white - 4000k

Dont know about 5000k, sounds non-standard - but must be close to true daylight.

Cheers

Looking for adventure.
In whatever comes our way.

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Reply By: Member - Ed. C. (QLD) - Thursday, Feb 07, 2008 at 13:12

Thursday, Feb 07, 2008 at 13:12
ThisKelvin should explain it... (Google is your friend;-))

In practical terms, a 3000K light will give a yellowish "soft" light.. generally referred to as "warm white", I believe, whereas a 5000K light is a very "white" light (commonly referred to as "cool white")....

Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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Follow Up By: Member - Ed. C. (QLD) - Thursday, Feb 07, 2008 at 13:16

Thursday, Feb 07, 2008 at 13:16
Hmmm..... looks like everybody spoke at the same time;-)))

looks like they're all sayin' pretty much the same thing, though:))

Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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Follow Up By: disco1942 - Thursday, Feb 07, 2008 at 21:32

Thursday, Feb 07, 2008 at 21:32
For those technically inclined there is a fuller explanation of colour temperature at http://en.wikipedia.org/wiki/Color_temperature

PeterD
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Reply By: Member - joc45 (WA) - Thursday, Feb 07, 2008 at 13:21

Thursday, Feb 07, 2008 at 13:21
My preference for camping is the 5000k CFL, as it seems to give more light than the 3000k (I have several of each in my kit).
At home, I prefer the softer 3000k, as the 5000k looks pretty harsh in the house.
Gerry
AnswerID: 286139

Follow Up By: Member -Signman - Thursday, Feb 07, 2008 at 13:27

Thursday, Feb 07, 2008 at 13:27
Thanks all for the details...
and to joc45- that's kinda what I needed to know..
Cheers to all
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Reply By: ben_gv3 - Thursday, Feb 07, 2008 at 13:56

Thursday, Feb 07, 2008 at 13:56
Think of 3000k as being close to the colour of a normal incandescent light whereas the 5000k is close to the normal fluro light.
I personally prefer a 3000k light as it's not as harsh as a 5000k light.
AnswerID: 286143

Reply By: Gronk - Thursday, Feb 07, 2008 at 14:14

Thursday, Feb 07, 2008 at 14:14
And just to confuse things in the case of HID lights.....the higher the Kelvin the less Lumens they put out.......ie; a 4000K HID throws out more light than a 8000K one !!!

The higher the K the whiter the light.....8 - 10000K ones will be blueish
AnswerID: 286145

Follow Up By: Member - joc45 (WA) - Thursday, Feb 07, 2008 at 16:11

Thursday, Feb 07, 2008 at 16:11
Interesting!
As per my post above, I found that the 5000k CFL gave better light than an equivalent wattage 3000k cfl.
Might be something to do with HIDs performing differently to CFLs, or the particular design of the 5000k units I use.
Gerry
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Reply By: mfewster - Thursday, Feb 07, 2008 at 18:14

Thursday, Feb 07, 2008 at 18:14
What a fun thread. And to be really really picky, water only boils at 100 Degress C at sea level, although this varies very slightly with atmospheric pressure at any given moment.
AnswerID: 286176

Follow Up By: F4Phantom - Thursday, Feb 07, 2008 at 22:26

Thursday, Feb 07, 2008 at 22:26
yes and water boils at 18 deg c on the tippy top of everest
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Follow Up By: Member - Olcoolone (S.A) - Friday, Feb 08, 2008 at 13:31

Friday, Feb 08, 2008 at 13:31
Water will only boil in a container that has a rough surface?

Put water in a 100% smooth container and it will not boil but it will super heat.
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Follow Up By: mfewster - Friday, Feb 08, 2008 at 14:03

Friday, Feb 08, 2008 at 14:03
Olcoolone. That's interesting. Do you mean it won't bubble, or do you mean that it won't start to change into a gas? Either way, I would have thought the temperature of the boiling point would still remain the same?? Dunno. Tell me more please.
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Follow Up By: Member - Oldbaz. NSW. - Friday, Feb 08, 2008 at 14:18

Friday, Feb 08, 2008 at 14:18
I boiled the billy the other day & had to chuck it out..water went
all lumpy......oldbaz.
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Follow Up By: mfewster - Friday, Feb 08, 2008 at 16:07

Friday, Feb 08, 2008 at 16:07
Old baz, yer a silly old sod. After all this time in the bush you should have known that it has to be stirred all the time to stop that happening and spoiling your cuppa.
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Follow Up By: Mike Harding - Friday, Feb 08, 2008 at 16:52

Friday, Feb 08, 2008 at 16:52
Superheating is well established:

Careful with that microwave

Mike Harding
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Follow Up By: mfewster - Friday, Feb 08, 2008 at 23:10

Friday, Feb 08, 2008 at 23:10
Thank you Mike H. I was not aware of that condition. One lives and learns
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Follow Up By: Member - Oldbaz. NSW. - Saturday, Feb 09, 2008 at 18:04

Saturday, Feb 09, 2008 at 18:04
Thanks for the advice Mike, you would, of coarse, not use a straight stick to do the stirring. :))).
That little anecdote came from an old fishing mate, sadly departed now, who would take great delight in gathering the kids around the billy & putting on a great act about having to chuck the water out. One of those things I'll never forget....like whatzisname !!!
cheers...oldbaz.
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Reply By: Mike Harding - Thursday, Feb 07, 2008 at 18:27

Thursday, Feb 07, 2008 at 18:27
Is there a physicist in the house? :)

Can anyone explain to me why there _is_ a minimum temperature of 0K?

Mike Harding
AnswerID: 286181

Follow Up By: Mike Harding - Thursday, Feb 07, 2008 at 18:27

Thursday, Feb 07, 2008 at 18:27
PS. That's "zero K" not OK :)
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Follow Up By: equinox - Thursday, Feb 07, 2008 at 18:36

Thursday, Feb 07, 2008 at 18:36
I'm not a physicist,

But there has to be a temperature of which no more heat can be extracted out - and that is 0 K.

You can't get colder than the coldest temperature possible - or you can't take heat out of something that already has all its heat taken out.

I can understand it perfectly, perhaps just can't describe it adequately.
Looking for adventure.
In whatever comes our way.

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Follow Up By: Member - Mike DID - Thursday, Feb 07, 2008 at 18:54

Thursday, Feb 07, 2008 at 18:54
Heat is an aspect of the atoms in a material being in motion.

Things can't get any colder than when all atomic motion stops - i.e -273 degC. Absolute Zero.
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Follow Up By: Mike Harding - Thursday, Feb 07, 2008 at 18:59

Thursday, Feb 07, 2008 at 18:59
Hi Mike

That was my understanding too but why does it occur at that particular temperature and why does it occur to all atomic structures?

Mike Harding
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Follow Up By: Member - Mike DID - Friday, Feb 08, 2008 at 19:12

Friday, Feb 08, 2008 at 19:12
You will have to ask Professor Julius Sumner Miller "why is it so".
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Reply By: MEMBER - Darian (SA) - Thursday, Feb 07, 2008 at 18:39

Thursday, Feb 07, 2008 at 18:39
Dave - "how ya goin ?"....... as I recall from Trade School (a wise old ex London Uni graduate) ..... and as others have said to a point.........and in "bushman's terms" :-o) .....1. Zero degs Kelvin is as cold as anything can get ! Really cold ... in fact no plurry heat at all...nothing.... about -275 degs C I think. 2. Incandescent materials give off light when they are hot. 3. All incandescent materials give off the SAME colour of light, at the same temperature. 4. Different types of light sources rated at the same K should give light of the same colour (even if they aren't incandescent sources - its just a rating system in those cases). Hell - the foregoing could even be true !
AnswerID: 286186

Reply By: BoldJack ( Penrith NSW) - Thursday, Feb 07, 2008 at 20:04

Thursday, Feb 07, 2008 at 20:04
G'Day Signman.
It doesn't really matter what you use ,as long as YOU don't use a gas bottle. LOL :-)
Cheers Bert.
AnswerID: 286201

Follow Up By: Member -Signman - Friday, Feb 08, 2008 at 09:24

Friday, Feb 08, 2008 at 09:24
Yea- Thanks Bert. I'll remember that !!
Hi to the family.
Keep Michelle away from the garage & give Emm a cuddle from Luke.
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Reply By: Footloose - Thursday, Feb 07, 2008 at 20:35

Thursday, Feb 07, 2008 at 20:35
As long as you lot are being picky....only water without impurities boils at 100C. Which is why your peas in water need to be slightly hotter :) And only water without impurities freezes at 0C.
AnswerID: 286209

Follow Up By: disco1942 - Thursday, Feb 07, 2008 at 21:29

Thursday, Feb 07, 2008 at 21:29
To continue the picking - water with something dissolved in it is no longer water - it's an aqueous solution.

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Follow Up By: Footloose - Thursday, Feb 07, 2008 at 21:34

Thursday, Feb 07, 2008 at 21:34
Is that when its partly or only fully dissolved :))
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Follow Up By: Footloose - Thursday, Feb 07, 2008 at 21:43

Thursday, Feb 07, 2008 at 21:43
I would guess as long as it doesn't change the water into something else.
For example H2SO45H2O isn't exactly water...but is it an aqueous solution ?
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Reply By: Member - Vincent A M (NSW) - Thursday, Feb 07, 2008 at 22:38

Thursday, Feb 07, 2008 at 22:38
did the fluoro's not fit that i gave you or are you after a different size
AnswerID: 286244

Follow Up By: Member -Signman - Friday, Feb 08, 2008 at 09:30

Friday, Feb 08, 2008 at 09:30
G'day Vince
Yup- the tubes fitted the 'hand lantern' just fine thanks.!!!
Have a good weekend sailing.
We got a win on the Sunday heat after the race was postponed for 1 1/2 hours with no wind. (I think a 5th on Saturday).
Catch ya next time- and thanks again..
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Reply By: crusher - Friday, Feb 08, 2008 at 02:50

Friday, Feb 08, 2008 at 02:50
Member Signman
If you have to ask that questing what you need to decide is do I want 300 or 5000 moths and bugs per hour,that's reality.
Good luck
Crusher
AnswerID: 286268

Follow Up By: Member -Signman - Friday, Feb 08, 2008 at 09:32

Friday, Feb 08, 2008 at 09:32
Hi crusher
Please explain ??
Which one would attract the bugs??
Cheers
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Follow Up By: Hughd - Friday, Feb 08, 2008 at 17:45

Friday, Feb 08, 2008 at 17:45
Glad to see the bug index raised. My experience is that cool white (higher temperature) attracts more bugs than warm white (lower temperature - there's a conundrum). I have even experimented with wrapping yellow cellophane around the fluoro to warm up the whiteness to pale yellow,
Cheers
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Reply By: PajeroTD - Saturday, Feb 09, 2008 at 02:18

Saturday, Feb 09, 2008 at 02:18
this website explains it pretty well. http://www.schorsch.com/kbase/glossary/cct.html

It's one of the first things you learn about in photography/video production, which effects white balancing.
AnswerID: 286481

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