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

ChoYunEL
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(Original post by FristyKino)
Lol'd at this so hard at 6am in the morning - probably not the best thing to do at this time lol
Glad I made you laugh
I was up at 5:30am and I have an exam at 9 >.>


I haven't looked at Nuclear Physics yet...
I'm more worried about medical though

Electrical field, Magnetic field, Capacitors, Fundamentals of atoms, Nuclear Physics, radiation, X-rays, Medical (Gamma Cam..), Ultrasounds, Space - formation of stars etc, Life of Space.
To the A2 book, EMI, Capacitors, Nuclear Physics, Medical, Space
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FristyKino
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(Original post by ChoYunEL)
Glad I made you laugh
I was up at 5:30am and I have an exam at 9 >.>


I haven't looked at Nuclear Physics yet...
I'm more worried about medical though

Electrical field, Magnetic field, Capacitors, Fundamentals of atoms, Nuclear Physics, radiation, X-rays, Medical (Gamma Cam..), Ultrasounds, Space - formation of stars etc, Life of Space.
To the A2 book, EMI, Capacitors, Nuclear Physics, Medical, Space
Well you have a day so you can go through nuclear physics - its not THAT bad.
I really struggle with magnetic fields and electromagnetic induction - for which reason i will be off ot college in 2 hours and lock my physics teacher in the classroom and only let him out till he has successfully taught me all there is to know about the two topics
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ChoYunEL
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(Original post by FristyKino)
Well you have a day so you can go through nuclear physics - its not THAT bad.
I really struggle with magnetic fields and electromagnetic induction - for which reason i will be off ot college in 2 hours and lock my physics teacher in the classroom and only let him out till he has successfully taught me all there is to know about the two topics
After my exam of course. And FP2 is rather bad so afterwards I would probably play games till I cheer up. Hopefully that will be before the physics exam

EMI was my favourite section... It's the medical bit cus it's all essay! I can't write what they want on the mark scheme - ever xD
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Ralphus J
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Can someone help with mass spectrometry please, thanks
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ChoYunEL
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(Original post by Ralphus J)
Can someone help with mass spectrometry please, thanks
Have a question you want to look at?

(Original post by ChoYunEL)
A Mass Spectrometry uses the principle of f = (m*v^2)/r
The Spectrometer will project/accelerate a substance of unknown material/substances through a magnetic and/or Electric field.
Force/Velocity^squared = Mass/Radius

Since you cannot change the mass of an material, a detector/collector picks up where the material is using the radius it has traveled through the magnetic field.

There are two types of mass spectrometer as far as I understand..
One which only allow one particular substance through a gap (using electric fields to stop additional ions)
And ones which has several detectors, without an electric field, which collects certain irons.
You asked this before
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Ralphus J
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Thanks Choy i dont think anyone answered lol :'(
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scotzbhoy
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(Original post by sulexk)
Larmor frequency and precession frequency are related, however the larmor frequency is the angular frequency of precession W=yB

where y=gyromagnetic ratio - depends on nucleus
B= magnetic flux density- of external magnetic field

Precession frequency = Larmor frequency / 2pi

I know, it seems complicated.

But to not complicate things, if they ask for precession frequency use that formula, if they ask for larmor frequency just workout W=yB

Think about it like this - how do you workout frequency x/2pi, where x is number of radians covered per second. when you divide this by 2pi you get the number of circles traversed per second. So you can see that the larmour frequency is the "angular frequency of precession".

Hope that helps- please donot hesitate to reply.

Thank you
We don't need to know that. We need to know what the Larmor frequency is, but not how to calculate it.
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LBenjamin93
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What are some SCIENTIFIC non-political advantages and disadvantages of using fusion and fission as ways to produce electrical power? my textbook is kind of useless and doesnt give enough, and the internet is just full of political answers(which aren't allowed) like how expensive it is. :confused:
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jam.wa
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(Original post by LBenjamin93)
What are some SCIENTIFIC non-political advantages and disadvantages of using fusion and fission as ways to produce electrical power? my textbook is kind of useless and doesnt give enough, and the internet is just full of political answers(which aren't allowed) like how expensive it is. :confused:
Fission
Advantages:
-Large amounts of energy produced for small amount of fuel
-No CO2 pollution

Disadvantages
-Energy must be used as it is generated
-Radioactive waste produced and must be stored
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M_I
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(Original post by magdaplaysbass)
dividing 18 by 0.15 will give you 1% of the power - which is 120
so you need to multiply it by 100 to get 100% of the power (12,000)
Thanks.

Any idea what's going to come up?
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muffingg
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In a bicycle dynamo, is the emf induced because of the rotation of the magnet in the coil of wire?

Does that mean that not just putting the magnet in and out of the coil produces an imf but also rotating the magnet in a coil?

In short: If you rotate a magnet inside a coil, does that produce an induced emf?

Thanks.
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M_I
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How does the cosmic background raditaion being linked with 3K prove the big bang model?
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sulexk
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(Original post by muffingg)
In a bicycle dynamo, is the emf induced because of the rotation of the magnet in the coil of wire?

Does that mean that not just putting the magnet in and out of the coil produces an imf but also rotating the magnet in a coil?

In short: If you rotate a magnet inside a coil, does that produce an induced emf?

Thanks.
Hello,

For a bicycle dynamo, the permanent magnet is rotated inside a coil of wire - this induces a current in the circuit and the light turns on.

So by rotating the magnet, the magnetic flux linkage is changing, and so if it is changing then it must have a rate of change, if the rate of change happens to be constant then you have steady induced EMF.

Hope that helps!
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jam.wa
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(Original post by M_I)
How does the cosmic background raditaion being linked with 3K prove the big bang model?
It's the fact that it is uniform at 3K which suggests when the universe was smaller, it was alot hotter, suggesting a big bang type thingy.
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sulexk
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(Original post by M_I)
How does the cosmic background raditaion being linked with 3K prove the big bang model?
The standard model predicts that the universe has an average temperature of about 2.7K.
It so happens that the radiation that has the same intensity everywhere(which was present during the big bang and stretched as it pervarded through space, due to cooling), also has a temperature of about 2.7k. How do we know it is 2.7k. It is because this radiation happens to be extremely intense in the microwave region, which corresponds to a temperature of 2.7K

Hope that helps!
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muffingg
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(Original post by sulexk)
Right hand rule or left hand rule.

Let us unravel this problem with an example. Suppose an aircraft is flying east to west, its wings are an electrical conductor cutting across the earth's magnetic flux. In the northen hemisphere, which wingtip will become positively charged?

This seems like a very challenging question at first, but really all we need to do is to find the direction of the force between the wingtips- telling us which direction the positive charge will be flowing. So we use flemings left hand rule for direction of force:

NOTE- northern hemisphere- so magnetic field into the paper, positive charge has a velocity east to west, since the positive charge is between the wings and so we have a current in the direction the plane is moving in, and now you can use flemings left hand rule to workout the direction of the force. So positive moving east to west, direction of magnetic field into the page, and it should give thumb going down the page. We can use the right hand rule to check if this is correct.
Using Right hand rule
magnetic field into the page, thumb east to west, what direction is induced current?

down the page(not into the page, down the page)

I hope this helps!
Thanks, but I don't quite understand what you mean. We use the left hand rule for this, right? And there isn't any emf induced or is there?

And which way would the magnetic fields be going if you are sitting inside the plane? I think they would be going from right to left since the North Pole would be on the right and the South pole on the left? (MFL go from North to south don't they?)
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superpope99
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Gaaah, I've got to revise most of Medical Physics and the Universe stuff. Any tips on doing this?
The one thing I'm finding at the moment is I'm struggling to differentiate between what we need to know, and the stuff in the textbook that's just sort of extra "did you know?" type stuff.
I have the revision guide, but it seems like that has too little of the stuff in. I don't really know how to go about this :/
I also have the ExamQuest software, have people found this useful in the past?
The sort of questions I struggle with are the ones where it says "Explain the principles of x-ray" for like 8 marks, and it's all there in my head, and I write down loads of correct information, but then the mark scheme means that I only get like 4/8, even though I know what I'm talking about, just not what they're asking. Does anyone else find this, and if so, how do you overcome it?

I know this is all pretty rambling, but AQA core 4 didn't go very well, which I needed for my A*, nor did Salter Chemistry F335, which I need an A in. Physics should be my redeemer, if I can get an A* in it, I'm just freaking out atm
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sulexk
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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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sulexk
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(Original post by muffingg)
Thanks, but I don't quite understand what you mean. We use the left hand rule for this, right? And there isn't any emf induced or is there?

And which way would the magnetic fields be going if you are sitting inside the plane? I think they would be going from right to left since the North Pole would be on the right and the South pole on the left? (MFL go from North to south don't they?)
If you are travelling in the northern hemisphere, then the magnetic field is going down(since the earth's north pole- is like a south pole-field lines going into). since the plane is travelling east to west- think about the positive charge between the wingtips(two ends of the wings)- they too have a velocity in the direction east to west so our current if we use the left hand rule is east to west, and we are trying to understand the direction of the force on this positive charge, which is moving between the wingtips. So magnetic field into the page, current east to west, and gives a force acting downwards(not into the page, but downwards).This tells us that the positive charge will moves towards the left wingtip making it positive.

I hope that helps, I can make it even more simpler if you want, but let me know if you have any questions please

This is a case of induced EMF(between the wingtips)
Thank you!
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M_I
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Is 2x10^10 = 20 billion?
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