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OCR Physics A - G485: Fields, Particles & Frontiers of Physics - June 2012

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    A Couple of questions:

    Am I right in thinking the that Universe cooled as it expanded due to the gain in gravitational potential energy as matter moved further apart?

    There was a question about why you can;t use the EMF induced between the wingtips of a flying aeroplane to power appliances, when the magnetic field perpendicular to the aeroplane is unoform then it'll be because the flux enclosed by a circuit on the aeroplane wouldn't change as it flies, but in reality the component perpendicular to the aeroplane would change, so would it be because the induced e.m.f. is very small?
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    What are the grade boundaries like for this module? I need a high C in this exam for an A. Not bothered about the A* as I need around 143/150.
    What mark (estimate) would I need in this module for a low B or high C? Cheers for the help in advance.
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    What are the grade boundaries like for this module? I need a high C in this exam for an A. Not bothered about the A* as I need around 143/150.
    What mark (estimate) would I need in this module for a low B or high C? Cheers for the help in advance.
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    (Original post by Toshiya)
    Yeah I'm relying on my G482 resit on Friday to give me a bit of slack in G485! I'm just struggling with it so badly!

    Don't worry, I think the grade boundaries were just unusually high in January! They're normally a little lower
    I got an A :O
    but it really doesn't count, cause we did a hour of the paper in the morning, and the rest later in the afternoon, so I revised everything I knew was on the paper that I couldn't do in between the sessions. :')

    Probably would've got an E maybe a D if it was one sitting
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    (Original post by balletlover)
    I got an A :O
    but it really doesn't count, cause we did a hour of the paper in the morning, and the rest later in the afternoon, so I revised everything I knew was on the paper that I couldn't do in between the sessions. :')

    Probably would've got an E maybe a D if it was one sitting
    They allowed that?! :O How come?
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    (Original post by Beth1234)
    They allowed that?! :O How come?
    It was only a mock we were doing in class :P
    I'd love it if that happened in the real exam like, haha!
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    (Original post by balletlover)
    It was only a mock we were doing in class :P
    I'd love it if that happened in the real exam like, haha!
    If we were allowed that in real life it would have been AMAZING

    I retook G482 today actually. No IDEA how it went... made a couple of daft mistakes I think, probably improved on my last score but not much!!!
    Time to crack on and really try and nail G485... /sigh :rolleyes:
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    Can finally catch up here now G482 is done and dusted. There's a big part of me that wants to feel more confident about this exam... not sure how possible that is though. Really worried that between this exam and G482 it could pull my average down to a C.

    Is there really as much universe crap to learn as it looks??? I got sick of reading medical and universe stuff. It;s so similar/ repetitive and I find it hard to differentiate between what's what
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    (Original post by Toshiya)
    If we were allowed that in real life it would have been AMAZING

    I retook G482 today actually. No IDEA how it went... made a couple of daft mistakes I think, probably improved on my last score but not much!!!
    Time to crack on and really try and nail G485... /sigh :rolleyes:
    Ohhh yeah my whole class except me resat that today :/ I resat it in January and did no revision for it, improved my D from year 12 to a C in G482, then got a U in the Newtonian World even though I like dedicated my life to revising it :') it was an awful paper though, hoping to improve loads. Hoping being the key word!
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    Has anyone made notes on Electromagnets?

    Describe a practical example of the field of a long solenoid?
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    S2 is out of the way now; I've started to focus on this exam just yesterday.

    I got 135/150 in G482 last summer, I'm aiming to better that in G485.
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    (Original post by Tripp)
    What are the grade boundaries like for this module? I need a high C in this exam for an A. Not bothered about the A* as I need around 143/150.
    What mark (estimate) would I need in this module for a low B or high C? Cheers for the help in advance.
    It's impossible to tell in advance. It depends on how hard the paper is judged to be. There was an Electrons, Waves and Photons paper a few years back that was so hard that 54% got you an A, whereas January's Newtonian World paper was so easy that you needed 60% for an E.

    Just try to do the best you can, and see what everyone else made of it afterwards to get a feeling for the boundaries.
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    (Original post by Z REFAN Z)
    Has anyone made notes on Electromagnets?

    Describe a practical example of the field of a long solenoid?
    The field inside the solenoid is largely uniform in strength and direction, and can be represented by straight lines of flux which extend outwards to form loops that go from the North to the South pole, and resemble that around a bar magnet.

    By practical example do you mean a real world device? If so a Helmholtz coil uses the combination of the fields from two coils to produce a uniform field between them, though the coils aren't called "solenoids" beacuse they aren't usually that long.
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    (Original post by XiaoXiao1)
    The field inside the solenoid is largely uniform in strength and direction, and can be represented by straight lines of flux which extend outwards to form loops that go from the North to the South pole, and resemble that around a bar magnet.

    By practical example do you mean a real world device? If so a Helmholtz coil uses the combination of the fields from two coils to produce a uniform field between them, though the coils aren't called "solenoids" beacuse they aren't usually that long.
    Thanks

    It was one of those outcomes on top of the pages but had no idea what to write down for it.
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    Can anybody quickly type out a basic few bullet points for the different stages of a MRI scanner please?

    Would be really appreciated
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    (Original post by OllyHV)
    Can anybody quickly type out a basic few bullet points for the different stages of a MRI scanner please?

    Would be really appreciated
    Taken from a mark scheme, question "describe MRI" or something along those lines.


    MRI
    • some nuclei behave as small magnets / certain nuclei possess a net spin / nuclei line up in the magnetic field (1)
    • Need for a strong magnetic field (1)
    • the frequency of precession is known as Lamor frequency (1)
    • Application of RF pulses (1)
    • produces resonance / flip energy states (1)
    • RF pulse turned off nuclei relax / flip back (and emit RF signal) (1)
    • RF detected (by coil receiver) and processed (1)
    • Use of non-uniform field / gradient field (1)
    • To locate position of nuclei in body (1)



    QWC mark: difference in the relaxation times for hydrogen in different tissues / materials
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    Would you still get marks if you wrote the answer how the mark scheme forms it? Rote learning I think the phrase is.
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    (Original post by Brap4k22DivideBy2)
    Would you still get marks if you wrote the answer how the mark scheme forms it? Rote learning I think the phrase is.
    Try and make it appear more natural but yeah you'd get the marks. If you're rushed for time bullet point.
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    (Original post by ebmaj7)
    Try and make it appear more natural but yeah you'd get the marks. If you're rushed for time bullet point.
    We've been told to bullet point all questions.
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    I'm quite looking forward to this exam, fields particles and the frontier of physics has my favourite topics

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