# Light bulbs, Wattage meaning? [closed]

Light bulbs, Wattage meaning?

Two incandescent bulbs (120 V, 25 Watt) and (120 V, 500 Watt) connected to the same batteries.

Which one shines brighter? And why?

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What determines how brightly a bulb shines is the amount of power it emits. Since the Watt is a measure of power... But there's one catch, this works only if the two bulbs are identical. Some bulbs are made to consume less energy but output more light. I looked for a reference and found this (scroll down a bit for a table). –  Jerry Apr 25 '13 at 18:00
Might be you need to clarify that you are talking about Incandescent light bulbs –  Val Apr 25 '13 at 18:02
@Jerry, thanks, Does that mean it is not the resistance that determines the brightness? –  richard Apr 25 '13 at 18:11
I disagree. The reason to close is absolute nonsense. The question is utterly abstract and "a must" for all. It is a scorn to say that it is narrow and useless for the others. –  Val Apr 25 '13 at 18:41
@Jerry. Wrong. Greater resistance => less current => less power => less temperature. Remember, I = U/R or P = U^2/R. R stands for resistance. You divide by it, not multiply. –  Val Apr 25 '13 at 19:02
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## closed as too localized by Waffle's Crazy Peanut, John Rennie, Qmechanic♦Apr 25 '13 at 18:37

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The bulb rated 500 W is doing more work per unit time, which implies that it is either emitting more light or just using up the energy to generate more heat. If both the bulbs have the same efficiency then it follows that the higher wattage bulb shines brighter.

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If question is wattage -> luminocity function then I think that there will be two components. One is that every watt is converted into a lumen (683 lm/W, to be exact according to Wikipedia). It is like $E=mc^2$: more mass = more energy. They are equivalent. So more power <=> more light. 500 is 20 times more than 25, which translates into 20x brighter.