June 2011 G485-Fields, Particles and Frontiers of Physics Watch

muffingg
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In a simple photographic flashgun a 0.20F capacitor is charged by a 9.0V battery. It is then discharged in a flash of duration 0.01s. Calculate the approximate resistance of the bulb.

How do you do that?

Answer in spoiler.

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0.025 Ohm


Edit- I'm not trying to test anyone or anything. I'm just confused how to get to that answer because my book says this is the answer to the question. I keep getting a different value than that.
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MarieLyon
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do we need to know the properties of charm, botom and top? And also do we need to know what makes up the pi and phi meson thing?
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MarieLyon
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#503
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(Original post by muffingg)
In a simple photographic flashgun a 0.20F capacitor is charged by a 9.0V battery. It is then discharged in a flash of duration 0.01s. Calculate the approximate resistance of the bulb.

How do you do that?

Answer in spoiler.

Spoiler:
Show
0.025 Ohm
please show how you got that answer
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apo1324
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#504
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(Original post by muffingg)
In a simple photographic flashgun a 0.20F capacitor is charged by a 9.0V battery. It is then discharged in a flash of duration 0.01s. Calculate the approximate resistance of the bulb.

How do you do that?

Answer in spoiler.

Spoiler:
Show
0.025 Ohm
I get 0.05Ohm. :L Damn.
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M_I
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#505
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(Original post by MarieLyon)
there's an equation for it isn't there? And that isn't ultrasounds its x-rays. isn't it?
Yes your right, but is that all we need 2 know, the equation??
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twistedinsanity
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#506
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(Original post by susan23)
Attachment 106628
ok what answer do you get for this for the total capacitance...show ur working.
I reckon 2. 3+3 is 6 for the parallel bit. Then 1/3 + 1/6 = 1/6+2/6=3/6=1/2. So take the reciprocal to get C, which is 2/1, ie 2 farads
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MarieLyon
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(Original post by M_I)
Yes your right, but is that all we need 2 know, the equation??
In the spec it just says about the thickness and the intial values.
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muffingg
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(Original post by MarieLyon)
please show how you got that answer

(Original post by apo1324)
I get 0.05Ohm. :L Damn.
I also got 0.05 Ohm as well. If someone else can confirm that 0.05 is the right answer it would mean my book is wrong. My book says 0.025. That's why I'm asking. :confused:
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susan23
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(Original post by twistedinsanity)
I reckon 2. 3+3 is 6 for the parallel bit. Then 1/3 + 1/6 = 1/6+2/6=3/6=1/2. So take the reciprocal to get C, which is 2/1, ie 2 microfarads or whatever the unit is.
Well done lol
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M_I
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#510
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(Original post by apo1324)
I get 0.05Ohm. :L Damn.
Working out?
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susan23
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(Original post by muffingg)
I also got 0.05 Ohm as well. If someone else can confirm that 0.05 is the right answer it would mean my book is wrong. My book says 0.025. That's why I'm asking. :confused:
I got 0.05 too but I think its wrong because...I found out initial Q from CV=Q and then found out current using Q=It and then used V=IR with V=9 but 9 is not the voltage across the resistor? is this how you did it?

I was thinking to use the exponential equation of Q=Q(initial)e^t/RC but we don't know Q?
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twistedinsanity
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(Original post by susan23)
Well done lol
Oh I though you were asking for help! haha ok my turn to post a q:

Explain how the nuclear fission reaction is able to produce energy. 2 marks
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sulexk
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#513
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(Original post by M_I)
Making more sense everytime I read something about it.....i hate Ultrasound.
I could be very wrong:

So far they have asked BIG| MARK questions on ultrasound and MRI. With that said, they also asked a mini question in jan on ultrasound. So its possible they could throw it in again- or not at all. I cannot find a paper from 2001 physics to g485, on PET, its new stuff, so they gotta test it at some point. They have done MRI and ultrasound already, so perhaps this time its PET's turn. They have asked about formation of a star and I believe olbers paradox in june 2010 - so it is possible that they could put a BIG MARKER in there on formaton of the universe.

In which I have put up a post already but here it is again:


A simple history of the universe, possible question:

Big bang
quarks and leptons existed freely ( at a temperature of around 10^14 K)
Quarks combined to form hadrons, such as protons (at a temperature of around 10^12 K)
atomic nuclei began to form by fusion ( at a temperature of 10^7K)
After 300,000 years atoms started to form as protons and helium nuclei grabbed electrons(temperature 10^4K). Note when the atoms formed there was more space for the radiation to move around in, so that the photons of radiation could pervade through space without being absorbed or deflected(this is what is meant by "the universe became transparent").

Then matter began to clump together(gravity became the dominant force) and stars, galaxies, gas clouds and dust began to form. It mentions in the book the temperature range for this occurence(10^3 K to 2.7K) - and that the universe is saturated with electromagnetic radiation with a characteristic temperature of 2.7K
Then we have |TODAY|

I hope this was not too much, any questions, please ask.

Thank you!
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M_I
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#514
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(Original post by MarieLyon)
In the spec it just says about the thickness and the intial values.
Ok....I'll have a look at the spec.
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muffingg
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#515
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(Original post by susan23)
I got 0.05 too but I think its wrong because...I found out initial Q from CV=Q and then found out current using Q=It and then used V=IR with V=9 but 9 is not the voltage across the resistor? is this how you did it?

I was thinking to use the exponential equation of Q=Q(initial)e^t/RC but we don't know Q?
That's how I did it too. I think my book might well be wrong !?
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TobeTheHero
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#516
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G485 is not that hard really it is all theory which is good and there is less calculations too!
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M_I
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(Original post by sulexk)
I could be very wrong:

So far they have asked BIG| MARK questions on ultrasound and MRI. With that said, they also asked a mini question in jan on ultrasound. So its possible they could throw it in again- or not at all. I cannot find a paper from 2001 physics to g485, on PET, its new stuff, so they gotta test it at some point. They have done MRI and ultrasound already, so perhaps this time its PET's turn. They have asked about formation of a star and I believe olbers paradox in june 2010 - so it is possible that they could put a BIG MARKER in there on formaton of the universe.

In which I have put up a post already but here it is again:


A simple history of the universe, possible question:

Big bang
quarks and leptons existed freely ( at a temperature of around 10^14 K)
Quarks combined to form hadrons, such as protons (at a temperature of around 10^12 K)
atomic nuclei began to form by fusion ( at a temperature of 10^7K)
After 300,000 years atoms started to form as protons and helium nuclei grabbed electrons(temperature 10^4K). Note when the atoms formed there was more space for the radiation to move around in, so that the photons of radiation could pervade through space without being absorbed or deflected(this is what is meant by "the universe became transparent&quot.

Then matter began to clump together(gravity became the dominant force) and stars, galaxies, gas clouds and dust began to form. It mentions in the book the temperature range for this occurence(10^3 K to 2.7K) - and that the universe is saturated with electromagnetic radiation with a characteristic temperature of 2.7K
Then we have |TODAY|

I hope this was not too much, any questions, please ask.

Thank you!
Thanks so much....no rep left 2 give.
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MarieLyon
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#518
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(Original post by muffingg)
That's how I did it too. I think my book might well be wrong !?
i used the three equations too. you cant use the expentional one because you dont have suffiecnt information
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Oh my Ms. Coffey
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Can anyone tell me about EMF produced by a AC. Generator.

Is this right?

EMF is Max when coil is parallel to the magnetic fields, EMF is 0 when it is perpendicular.
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susan23
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#520
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(Original post by muffingg)
That's how I did it too. I think my book might well be wrong !?
yaaa probs is!!

Guys, what do you think is most likley to come up in this exam??????????????????????
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