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OCR Physics A G485 - Frontiers of Physics - 18th June 2015

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edit: nevermind, question solved ^_^
(edited 9 years ago)
Reply 61
Could someone explain to me in a simple yet effective way the function of each part of a nuclear reactor or give some materials that explain it well.
Original post by L'Evil Fish
Here we go! We can discuss exam questions or general content if you need help.

I won't be revising for a while but if I can help, I'll try, means less revision for me in the summer if I help people earlier on (or if people explain to me!)

We haven't started yet! Going to start Cosmology when back. Will update OP with resources whenever.

G484 Thread


Why do you think the Grade boundaries for this paper are generally about 10 marks higher than G482?
Original post by ForgottenApple
Why do you think the Grade boundaries for this paper are generally about 10 marks higher than G482?


Haven't made it harder yet, but I think this year we will see a drop

G485 is a lot more written than G482 as well, which means people can rote learn
Original post by L'Evil Fish
Haven't made it harder yet, but I think this year we will see a drop

G485 is a lot more written than G482 as well, which means people can rote learn

Oh is there typically more written? We've still got to do medical and cosmology so im guessing it's there?
Original post by ForgottenApple
Oh is there typically more written? We've still got to do medical and cosmology so im guessing it's there?


Medical is a bunch of 6-8 markers...
Astronomy has a bit of maths but again 5-7 markers
Original post by L'Evil Fish
Medical is a bunch of 6-8 markers...
Astronomy has a bit of maths but again 5-7 markers

Have you finished it yet? What do you reckon are the hardest topics?
Original post by ForgottenApple
Have you finished it yet? What do you reckon are the hardest topics?


Not finished so I can't say tbh, it's just a lot of words I think
Original post by L'Evil Fish
Not finished so I can't say tbh, it's just a lot of words I think

what you doing for revision atm?
Original post by ForgottenApple
what you doing for revision atm?


Did a G484 past paper!

Didn't have to revise because it's all just mechanics/common sense it seems

Not done anything for G485
I'm doing all physics units cos I need an A overall. In G481 and 2 I'm getting good A's. In G484 I'm just about getting A's. I find G485 pretty straightforward apart from Electric and magnetic fields as well as capacitors. I can do the basic definition and calculation but I sort of stumble on sort of the harder questions. I've been doing a lot of past paper questions and regardless of looking at the mark scheme and seeing how its done, I occasionally get around 80% in those topics? Any advice?

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Original post by L'Evil Fish
Did a G484 past paper!

Didn't have to revise because it's all just mechanics/common sense it seems

Not done anything for G485


What content have you got left?

I have got half of the nuclear physics and the cosmology left.
Original post by Damien_Dalgaard
What content have you got left?

I have got half of the nuclear physics and the cosmology left.


Most of medical
And rest of the electromagnetic stuff
Original post by L'Evil Fish
Most of medical
And rest of the electromagnetic stuff


Just look at past mark schemes for medical and ingrain the medical physics answers i.e. MRI, CAT scans etc.

Do you have links to the 2014 papers pls?
Original post by Damien_Dalgaard
Just look at past mark schemes for medical and ingrain the medical physics answers i.e. MRI, CAT scans etc.

Do you have links to the 2014 papers pls?


I'm trying to look for them too! I'll let you know if I get them

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Original post by lollipopsftw
I'm trying to look for them too! I'll let you know if I get them

Posted from TSR Mobile


likewise :smile:
Reply 76
Original post by lollipopsftw
I'm trying to look for them too! I'll let you know if I get them

Posted from TSR Mobile


Original post by Damien_Dalgaard
likewise :smile:


Did you guys find these papers?
Can someone explain the process of a loop wire going into a magnetic field and refer to Faradays Law, my notes are completely messy thus wrong :L

Heres what I conclude so far

o As wire goes in, the area in t
he magnetic field increases so theres a change in magnetic flux linkage (NBA) thus emf is induced but in opposite direction (?) hence it is negative

o but when it is fully in the magnetic field, theres no change in magnetic flux linkage because N,B,A is all constant

o as it leaves the magnetic field, the area within the magnetic field decreases instead thus ...idk then something emf positive
Original post by Makashima
Can someone explain the process of a loop wire going into a magnetic field and refer to Faradays Law, my notes are completely messy thus wrong :L

Heres what I conclude so far

o As wire goes in, the area in t
he magnetic field increases so theres a change in magnetic flux linkage (NBA) thus emf is induced but in opposite direction (?) hence it is negative

o but when it is fully in the magnetic field, theres no change in magnetic flux linkage because N,B,A is all constant

o as it leaves the magnetic field, the area within the magnetic field decreases instead thus ...idk then something emf positive


Faradays Law:

The induced emf is directly proportional to the rate of change of flux linkage.

Lenzs' Law:

The direction of an induced emf/current is always in a direction as to oppose the change that caused/produced the induced emf/current.

So:

Bringing North end of magnet into a solenoid...

--> emf induced in coil because there has been a change in the magnetic flux through the coil.
--> in order to oppose the change, the side of the solenoid closest to the magnet must be North.
--> for this to occur, the current is anticlockwise when viewed from the face of the magnet

Removing North end of magnet

--> emf induced in coil because there has been a change in the magnetic flux through the coil.
--> in order to oppose the change, the side of the solenoid closest to the magnet must be South
--> for this to occur, the current in clockwise when viewed from the face of the magnet.

I hope this helps.

I think what I'm saying is correct but does anyone have anything to add or change?




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Original post by Hilton184
Faradays Law:

The induced emf is directly proportional to the rate of change of flux linkage.

Lenzs' Law:

The direction of an induced emf/current is always in a direction as to oppose the change that caused/produced the induced emf/current.

So:

Bringing North end of magnet into a solenoid...

--> emf induced in coil because there has been a change in the magnetic flux through the coil.
--> in order to oppose the change, the side of the solenoid closest to the magnet must be North.
--> for this to occur, the current is anticlockwise when viewed from the face of the magnet

Removing North end of magnet

--> emf induced in coil because there has been a change in the magnetic flux through the coil.
--> in order to oppose the change, the side of the solenoid closest to the magnet must be South
--> for this to occur, the current in clockwise when viewed from the face of the magnet.

I hope this helps.

I think what I'm saying is correct but does anyone have anything to add or change?




Posted from TSR Mobile


I wasnt referring to the solenoid N/S poles but just a constant magnetic field and a loop of wire, but thanks anyway

For solenoid I suppose you refer to magnetic flux because the magnet is at 90 degree thus no need to talk about magnetic flux linkage

Sorry shouldve been cleaaar

But I suppose the answer is different for both the N/S solenoid and constant field+wire?

Because for the constant B field, I would use flux linkage instead of flux, because the area is changing? Is this correct Hmmm

Hmmm Idk, sorry

Btw thanks for explaining the solenoid, I finally understand it...I actually gave up to understand the concept yet you helped to understand much better than my teacher lmao

So what should I refer to linkage or flux only


the reason why im saying linkage instead of flux because as a the loop of wire goes in , the amount area of wire goes in is increasing so there is a change in magnetic linkage

idk

halp meh pls
(edited 8 years ago)

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