They don't have a clue...

[watercooled]

Just read the answers the the guy's question: http://answers.yahoo.com/question/in...4222442AAwo6yf
Really, why did they bother answering?

Also, for added enjoyment: http://answers.yahoo.com/question/in...2013222AAZUT96

[Whiternoise]

I'm guessing the 100W bulb has a lower resistance? Seems silly to assume that both are drawing the same current - which is how they get their results. If they did then as P = IV, they'd both consume the same amount of power - the wall outlet should be providing a uniform 240V or whatever!

It's an honest mistake though.

Explanation for anyone who's confused: http://forum.audiogon.com/cgi-bin/fr...2&openflup&7&4

[watercooled]

I'm just surprised at how many people got it completely wrong!
The facts (I'll spare you the maths as much as possible): the 100W bulb draws more power (obviously) so therefore more current because they are both at the same voltage. More current=LOWER resistance (what they are saying is higher resistance=more current which is wrong, think of it this way - a true short circuit has no resistance and draws tons of power until something melts).
They also say that the thicker filament has more resistance - wrong again, for a given conductor, a thicker sample has a LOWER resistance.
I just feel sorry for the guy who asked the question - he's more confused now than he was to start with!

[peterb]

Power =(v^2)/R

R=(v^2)/P

Assuming the same voltage for both, then higher the power, the lower the resistance. (Intuitive really.

Wait until they start asking about impedance!

[watercooled]

Power =(v^2)/R

R=(v^2)/P

Assuming the same voltage for both, then higher the power, the lower the resistance. (Intuitive really.

Wait until they start asking about impedance!

Should be fun

I've just worked it out roughly - the 100w bulb has a resistance of roughly 530ohms, 60w = roughly 880 ohms (hot resistance that is ie when the bulb is on). Forgive me if I'm missing something but 880 looks bigger than 530 to me...
I'm pretty sure we covered that even in GCSE!!

[Whiternoise]

Voltage from the outlet is 240V, we want a power of 100W, so P = IV, a current of 0.41A. P = I^2 R, so the resistance needed is: 560Ohm. Doing the same for the 60W, gives a resistance of 960Ohm.

I'm assuming an outlet voltage of 240.

I don't see a problem there (or was that sarcasm!)

EDIT: Right that was sarcasm, my bad

[peterb]

Should be fun

I've just worked it out roughly - the 100w bulb has a resistance of roughly 530ohms, 60w = roughly 880 ohms (hot resistance that is ie when the bulb is on). Forgive me if I'm missing something but 880 looks bigger than 530 to me...
I'm pretty sure we covered that even in GCSE!!

No you aren't that is correct Actual value depends on the voltage you took, but right ballpark)

[Steve]

What if the filament has a resonant frequency of 50Hz?

[watercooled]

I took voltage as 230v and rounded the numbers to 2SF. And yes, it was sarcasm

[peterb]

What if the filament has a resonant frequency of 50Hz?

The main component will be resistive, so the Q factor will be so small that electrical resonance wouldn't be an (and would depend on whether it was parallel resonant or series resonant.

However mechanical resonance would be a factor, with the interaction withthe earth's magnetic field causing it to vibrate, and so if it was mechanically resonant, it could vibrate itself to bits!

HTH

[Steve]

http://www.youtube.com/watch?v=13eDfrMgFQM#t=32

My filament is more selective than your filament

[Brucelles]

I wonder why people aren't taught the old hosepipe analogy for resistance. A thick (wide) hosepipe allows more water through = Less resistence, a narrow hosepipe, like a thin wire offeres more resistance. Simple.

But really, yes. If you know that you don't know, why answer?

[watercooled]

I wonder why people aren't taught the old hosepipe analogy for resistance. A thick (wide) hosepipe allows more water through = Less resistence, a narrow hosepipe, like a thin wire offeres more resistance. Simple.

But really, yes. If you know that you don't know, why answer?

That's pretty much how I was originally taught, and how I would explain it to someone who doesn't understand properly. The funny thing is they seem so sure about what they are saying.

[mmh]

That's pretty much how I was originally taught, and how I would explain it to someone who doesn't understand properly. The funny thing is they seem so sure about what they are saying.

thats because theyre on the internet, and on the internet the person posting is ALWAYS right

[0iD]

How Many Computer Geeks on a Forum Does it Take to Change a Light Bulb?
1 to change the light bulb and to post that the light bulb has been changed.

14 to share similar experiences of changing light bulbs and how the light bulb could have been changed differently.

7 to caution about the dangers of changing light bulbs.

6 to argue over whether it's "lightbulb" or "light bulb"

Another 6 to condemn those 6 as stupid.

2 industry professionals to inform the group that the proper term is "lamp".

15 know-it-alls who claim they were in the industry, and that "light bulb" is perfectly correct.

19 to post that this forum is not about light bulbs and to please take this discussion to a light bulb forum.

11 to defend the posting to this forum saying that we all use light bulbs and therefore the posts are relevant to this forum.

36 to debate which method of changing light bulbs is superior, where to buy the best light bulbs, what brand of light bulbs work best for this technique and what brands are faulty.

5 People to post pics of their own light bulbs.

7 to post URL's where one can see examples of different light bulbs.

4 to post that the URL's were posted incorrectly and then post the corrected URL's.

13 to link all posts to date, quote them in their entirety including all headers and signatures, and add "Me too".

5 to post to the group that they will no longer post because they cannot handle the light bulb controversy.

4 to say "didn't we go through this already a short time ago?"

13 to say "do a search on light bulbs before posting questions about light bulbs".

1 to bring politics into the discussion by adding that George W. isn't the brightest bulb.

4 more to get into personal attacks over their political views.

1 forum lurker to respond to the original post 6 months from now and start it all over again

4 to post that it is their constitutional right to change a light bulb.

3 to argue that all light bulbs should be banned

1 moderator to lock the light bulb thread.

[peterb]

Unless it's a Microsoft engineer - in which case it takes none as darkness will be defined as a new standard.