# June 2011 G485-Fields, Particles and Frontiers of PhysicsWatch

7 years ago
#761
(Original post by Oh my Ms. Coffey)
Unit 1, well they had some unit 1 projectiles in the first mock paper for electric fields so I dont think so maybe some density. Unit 2 is much more likely.
capacitors? i love capacsss
1
7 years ago
#762
(Original post by Oh my Ms. Coffey)
(8piGp/3)^-0.5 = Age I think.

p = Density
G = Newtons gravitational constant
That's using the formula for the critical density of the universe, not the actual density of it. We can only give the possible fates using that.

Edit: Actually, that gives us the average density, the critical density is the density required for it to be flat..my mistake!
0
7 years ago
#763
(Original post by XST)
That's using the formula for the critical density of the universe, not the actual density of it. We can only give the possible fates using that.

Not sure how you would answer the question..
Current estimates of the density of the universe are close to the critical density though.
0
7 years ago
#764
0
7 years ago
#765
Let's all have a Physics conservation.
0
7 years ago
#766
Bed time for me
1
7 years ago
#767
Oh my days I'm such a nerd, I just memorized the whole of the evolution of the universe, the exact times, temperatures and everything.

Oh my days such a nerd...
0
7 years ago
#768

Could you give me a model answer to the above question please

okay basically the picture wont work but its the one about MRI scanner june 2010 Q5
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7 years ago
#769
(Original post by MRHellen)

Could you give me a model answer to the above question please

okay basically the picture wont work but its the one about MRI scanner june 2010 Q5

1. Protons possess a property known as spin
2. In a strong magnetic field, the protons line up and all precess around their axis at the same frequency (Larmor Frequency)
3. A radiofrequency is applied at the Larmor frequency causing the protons to become excited and flip on their axis.
4. Depending on the protons' environment, they will relax at different times and emit an identical radio frequency to the one absorbed.
5. Relaxtion time allows you to know the material in which the proton exists.
6. Small magnets can be placed to create a gradient in the magnetic field.
7. This changes the Larmor frequency at specific points, and a specific radio frequency can be applied to those points.
8. This allows the computer to know in 3D where the proton is in the body and the type of material it is in.
0
7 years ago
#770
How many marks is it?
0
7 years ago
#771
(Original post by Oh my Ms. Coffey)
Bed time for me
Jesus, I could never sleep this early.
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7 years ago
#772
(Original post by Oh my Ms. Coffey)
Bed time for me
Me too me thinks.

A long day that began with C4 and another early start tomorrow for Physics and General Studies... .. May read me book for an hour first though
0
7 years ago
#773
(Original post by XST)
1. Protons possess a property known as spin
2. In a strong magnetic field, the protons line up and all precess around their axis at the same frequency (Larmor Frequency)
3. A radiofrequency is applied at the Larmor frequency causing the protons to become excited and flip on their axis.
4. Depending on the protons' environment, they will relax at different times and emit an identical radio frequency to the one absorbed.
5. Relaxtion time allows you to know the material in which the proton exists.
6. Small magnets can be placed to create a gradient in the magnetic field.
7. This changes the Larmor frequency at specific points, and a specific radio frequency can be applied to those points.
8. This allows the computer to know in 3D where the proton is in the body and the type of material it is in.
Cheers rob
0
7 years ago
#774
Why does fusion produce more energy than fission?
0
7 years ago
#775
all nighter for me just had 4 hours sleep
0
7 years ago
#776
who is with me?
0
7 years ago
#777
When they ask us to define the Farad or Weber, can you just quote the equation with units? Or do you actually have to learn the definition?
0
7 years ago
#778
(Original post by CoffeeStinks)
Why does fusion produce more energy than fission?
fusion reaction binds to nuclei with a small binding energy per nucleon into a nuclei with a very higher binding energy per nucleon.

in a fission reaction the binding energy per nucleon does increase, but not by a lot
0
7 years ago
#779
(Original post by CoffeeStinks)
Why does fusion produce more energy than fission?
the difference between the binding energy per nucleon is greater in fusion
0
7 years ago
#780
Am I the only one doing all nighter!
1
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