physics help
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anyone pls?
http://img353.imageshack.us/my.php?image=ccf1105200800000rw0.jpg
http://img353.imageshack.us/my.php?image=ccf1105200800001ht7.jpg
setImgWidth();
Edit: Help display images
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thick means less resistance.
long mean more resistance.
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i know but
half the diameter is 4 times the resistance rite?
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yah
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Originally posted by ZedNg:
i know but
half the diameter is 4 times the resistance rite?
Because resistance is indirectly proportional to area
and area is proportional to the square of the diameter
You should know the formula
R = pl/A
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oh i saw it now
that question is area not diameter
but then the light bulb one leh?
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Larger resistance will have brighter light because power used is more.
From here, you should be able to find that ans is either A or D.
Filament X is thicker (lesser resistance) and shorter (also lesser resistance), hence Y has higher resistance
Thus, answer is D.
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but ur case is only if the bulb are connected in series,which is not stated(only say connected to mains)
but the bulbs are connected separately i.e diff circuit since they say connect to mains
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Originally posted by ZedNg:
oh i saw it now
that question is area not diameter
but then the light bulb one leh?
Obvious A and C are out.
Connected to mains, means same voltage. So it's easier to use P=V^2/R to determine brightness.
So the one with the smaller R is brighter.
Answer: B
EDIT: I assume different circuit. I went through this question in Victoria School Prelim Paper before.
If it's same circuit, then V will be different. But current in a series circuit is same throughout. So use P=I^2xR
Answer: D (if same circuit in series)
If parallel, then it's B. Can figure?
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my teacher say the ans is b but my teacher tend to give diff answer from the answer key. he like almost never agree with the tys ans key
EDIT: my teacher have the same explaination as garrick but my question is u should assume that is the circuit is separated?
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Ambiguous question. Pity we can't shade both.
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this question also appear on last yrs paper
in the exact same way
so i dunno man
i am ****ing confused
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If everything else is the same,
smaller resistance ==> brighter bulb, since E = I^2Rt
solve accordingly
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btw thx eagle for helping me with the pic
not too sure how to operate the functions
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Garrick is right in his explanations
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so assume or not assume?
that is the question
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here's what i think.
set up a series connection. insert bulb 1. note the brightness.
remove bulb 1. insert bulb 2. note the brightness.
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Originally posted by skythewood:
here's what i think.
set up a series connection. insert bulb 1. note the brightness.
remove bulb 1. insert bulb 2. note the brightness.
In physics, we don't do qualitative reading. It is too debatable. We do quantitative reading.
By the way the only way to measure light intensity is data logger, so bo bian do qualitative reading lor...
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Originally posted by Garrick_3658:
In physics, we don't do qualitative reading. It is too debatable. We do quantitative reading.
By the way the only way to measure light intensity is data logger, so bo bian do qualitative reading lor...
what the hell is qualitative reading, and what has it got to do with the question?
is what i described wrong or fundamentally flawed? so the correct setup is to connect both bulbs at the same time?
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Originally posted by skythewood:
what the hell is qualitative reading, and what has it got to do with the question?
is what i described wrong or fundamentally flawed? so the correct setup is to connect both bulbs at the same time?
Qualitative reading is just to use your senses and ASSUME a result.
For example: Which is heavier, a stone or a feather?
If you say feather STRAIGHT AWAY, then it's qualitative reading. Prove? Hold and see which one heavier.
If you use an electronic balance and weigh them, THEN say it's feather, that's quantitative reading. Prove? The stone is 100g while the feather is 0.1g.
Back to question: Assume they are connected in DIFFERENT circuits, separately. For me, that is. Ask eagle to confirm maybe. He's the senior around here.
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I think we should assume that it is connected to different circuits.
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so final verdict is assume?
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Originally posted by Garrick_3658:
Qualitative reading is just to use your senses and ASSUME a result.
For example: Which is heavier, a stone or a feather?
If you say feather STRAIGHT AWAY, then it's qualitative reading. Prove? Hold and see which one heavier.
If you use an electronic balance and weigh them, THEN say it's feather, that's quantitative reading. Prove? The stone is 100g while the feather is 0.1g.
Back to question: Assume they are connected in DIFFERENT circuits, separately. For me, that is. Ask eagle to confirm maybe. He's the senior around here.
i see, so what has that got to do with the question? is noting the brightness of the circuit a hard thing to do, and something that needs to be assumed? can't you just look at the bulb and say hey, it's less bright than that one?
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Originally posted by eagle:
I think we should assume that it is connected to different circuits.
agreed, different circuits, similar set ups.
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Take it as either different circuits, or parallel circuits.
Either way, the power will be V²/R because it is easier to determine the voltage, which means that the answer is B
If it is the bulbs are connected to the mains and are for usuage, it doesn't really make much sense to connect light bulbs in series. If one bulb fused, the other bulb wouldn't light up. This is the reason why electrical applicances in our home are connected in parallel.
