rjvh

in my oppinion even the acoustic waves turn into heat energy cause they will vibrate the moluculs they hit and that transfer has a loss and if molecules vibrate harder they create heat
you can't lose energy you only can transfer it to an other form and till the day of today you can't do it without loss
but in the majority of all transformations the losses will be represented in thermal form

crashsite

Head on over to the kennel. The residents there wont ignore you. If fact, they are pretty much constantly chanting, "Roff, Roff, Roff".

Oznog

Yeah Nigel you're WAY off there. The lion's share of power goes into electronics and drives and stuff. There's a fraction of a watt in desired sound out of the speakers in typical use, seeing as usually the PC makes a sound <1% of the time it's actually much less total power.

Your monitor estimate is also way off. Well, if you've ever seen a 5W LED flashlight it really lights up the room and IIRC that's only about 1W of actual light energy. So I'd say a CRT actually puts out light on the order of 1W of light energy. Again, using a Kill-A-Watt- a big desktop with a 21" monitor can suck down 250W continuously easy.

I've been in computer rooms though where they spent a lot to make the air conditioning REAL cold for the servers to lower the MTBF.

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Nigel Goodwin

You're comparing a narrow beam torch with a large glass screen, while the screen isn't as concentrated, it provides a far more even light distribution - far more than one watt.

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Oznog

Not at all. A 5W LED flashlight shined on a white wall, pulled back so it illuminates roughly the same area as a monitor, will easily make a brighter area than the monitor.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

Hero999

That's what I meant but a small amound of sound will leave the room, through the floorboards and windows.

About 0.25W seems more reasonable to me.

I doubt that.

Did you read my post about a 100W light bulb?

A 100W light bulb only gives 2.6W of light and I don't know how many times brighter it is than TV with a white screen; given the eye's logarithmic response, I'd estimate it's ten times a bright, that's 260mW of light.

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rjvh

electricalpower consumption is measured in watt but light is measured in candela and the amount of light that is send (Reflected) in a certian angle is mesured in lumen

and yes a LED is far more efficient in producing light in the visible spectrum than a crt does
don't forget that a crt also emit x rays that is a spectrum we can not see but it it takes the energy for producing it

the output in the for human visible spectrum is just a part from the total spectrum it emits

Robert-Jan

crashsite

But, there is an equivalency between candles and watts since both represent power. It's just the units of measurement that are customarily used.

It is difficult to equate an LED to an incandescent bulb for the reasons you give but, the discussion is about power efficiency and thus, taking into account the "wasted" power (heat rather than light) is valid.

The CRT (and associated parts...circuitry, filament, grid power, sweeping, high voltage, beam resistance, shadow mask losses, phosphor efficiency, etc.) uses power and one of those is X-ray emmission. But, again, for purposes of the direction this discussion has gone, they all result in heat and virtually all that heat is sinked by the room (and eventually by the world and then the universe at large).

So, while the things you say are true, I'm not just sure of the point you are making about the heat load contributed by the aappliances in a home.

rjvh

straying off the subject is happend quit a few replies aggo when it shifted to the effect a LED has on what we can see and a CRT in the same set up

i agree and mentioned in an earlyer reply that the majority of energy transformations has losses in a thermal form and so warm up the envoirment (as big as that you will name it )

now i just wonder (and i agree this is straying off topic)
with an ever expanding universe doesn't that mean to keep the avarage temp the same we have to produce heat energy otherwise we freez to death at a certain time

crashsite

It is my opinion (though perhaps not generally agreed to by some or even most) that, after a topic has been explored, a thread should diverge. That's how we broaden our views on a topic.

Of course the universe will cool as it expands (and radiates away light-speed energy, which will never be recovered...at least that's my SWAG (silly, wild-ass guess)). I'm writing a paper on the universe and I think the 3 degree background radiation is a cool remnant of an earlier iteration of our universe. But, THAT's really getting off topic!

Oznog

That's a critically flawed way of measuring light. When the room is dark, the eyes adapt and can read in light thousands, even millions, of times fainter than "normal" light. This highly advantageous adaptation makes it impossible to gauge the intensity of light sources.

I can read by an LED flashlight at from quite a ways away, with it illuminating a pretty decent area, a few sq feet. Usually those should be around 4V @ 20mA, 10% efficient could be 8mW of light.

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