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AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] Watch

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    Hello guys, I know the unit for Flux Linkage is Wb Turns, but I missed of the turns and wondering if they have any lenience to this, for some reason I think it's come up before.
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    Does anyone agree with this:
    Over the past 5 years, the unit 4 paper difficulty has varied only slightly. June 2014 was hard (I thought) yet the grade boundaries were high. The grade boundaries, for 120 ums at least, have only increased.
    69,67,63,63,62,62,61
    These are the raw marks for 120 ums going from most recent.
    The june 2015 paper wasn't hard but it wasn't easy- so the grade boundaries should be average. Does anyone have any estimations for A*? last year was 61, so i think it may be higher
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    (Original post by oonic0rn)
    ahhaah i need closure!!
    aha you say that now :P
    any chance you remember how many marks the electric field, work done and emf questions were worth?
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    (Original post by RemainSilent)
    For P and Q what would you think I would get to :

    (i) Current flowing through (which has magnetic flux) this with less resistance initally hence the reading on ammeter would be high (mentioned about flux cutting too)

    (ii) There is resistance so accoring to R= 1/CUrrent, if resitance is high current would e low hence the reading on ammeter would be less than in (i)

    Would this gain few marks?
    In (i) there's a sudden change in flux through Q so a current flows in Q. After that, the flux through Q is no longer changing to there is no current in Q. Result is that the ammeter deflects and then returns back to reading zero.

    (ii) There's a sudden decrease in current through P, so a sudden decrease in flux through Q so a current is induced in Q in the opposite direction to when the switch was closed (before, there was an increase in flux). Then afterwards the flux through Q is constant so no current in Q. Result is that the ammeter deflects in the opposite direction to before and then returns to zero.

    There was nothing to suggest that the current in Q in (ii) should be less than that in part (i).
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    look, hard paper or not, its all relative. Wev all found those wordy questions difficult and it was easy to lose marks on the rest of Section B today. that being said it wasn't a particularly challenging section A althought 4 or 5 where kinda discriminating. what im saying is they could have given us the easiest paper ever, but if WE AS A NATION did awful then the boundaries would be low. Today, if people are saying its easy then the boundaries may not fully reflect this as its all about how we actually did
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    Unofficial Mark Scheme

    Start posting everything you can remember about the questions/answers here and I'll update the first post as we go along.
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    (Original post by JizzaStanger)
    In (i) there's a sudden change in flux through Q so a current flows in Q. After that, the flux through Q is no longer changing to there is no current in Q. Result is that the ammeter deflects and then returns back to reading zero.

    (ii) There's a sudden decrease in current through P, so a sudden decrease in flux through Q so a current is induced in Q in the opposite direction to when the switch was closed (before, there was an increase in flux). Then afterwards the flux through Q is constant so no current in Q. Result is that the ammeter deflects in the opposite direction to before and then returns to zero.

    There was nothing to suggest that the current in Q in (ii) should be less than that in part (i).
    wouldnt the resistor affect it tho ?
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    (Original post by ShutUpLegs)
    Unofficial Mark Scheme

    Start posting everything you can remember about the questions/answers here and I'll update the first post as we go along.
    Shall I do this in the first post? It would be best for everyone to PM me as much as they can remember!


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    (Original post by DomRauba)
    Hello guys, I know the unit for Flux Linkage is Wb Turns, but I missed of the turns and wondering if they have any lenience to this, for some reason I think it's come up before.
    I'm pretty sure just Wb is fine
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    (Original post by CD223)
    Shall I do this in the first post? It would be best for everyone to PM me as much as they can remember!


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    Good idea to put the answers there when agreed upon but I think it's good to have a dedicated place to discuss/argue about questions without general chatter
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    (Original post by Jed-Singh)
    look, hard paper or not, its all relative. Wev all found those wordy questions difficult and it was easy to lose marks on the rest of Section B today. that being said it wasn't a particularly challenging section A althought 4 or 5 where kinda discriminating. what im saying is they could have given us the easiest paper ever, but if WE AS A NATION did awful then the boundaries would be low. Today, if people are saying its easy then the boundaries may not fully reflect this as its all about how we actually did
    There is SOME truth to that, but you need to consider that AQA have their own beliefs such as 'this question wasn't that hard so we wont drop the boundaries that much due to how many students got this incorrect'

    Also AQA know we are bad at physics exams - its the truth as an average they just know. A good example is for the passed 5 years they figured the average for MC was 16.5/25. and the boundary is still 19 for an A. I really think an A* will remain at around 58/60 ish.

    I was thinking this morning on the way to the exam that in other exams like Maths, its more like its us Vs the rest of the country's students that sit that exam. But with physics its such a big deal that they make this harder so they just set the grade boundaries accordingly.
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    (Original post by ShutUpLegs)
    Good idea to put the answers there when agreed upon but I think it's good to have a dedicated place to discuss/argue about questions without general chatter
    Sure. Can someone find Merhdad's answers to the MC? So we can debate them?


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    (Original post by RemainSilent)
    wouldnt the resistor affect it tho ?
    Yes but it's the rate of change of flux that counts. If the current through P changed more quickly when the resistance was changed than when S was closed (unlikely but not impossible, the converse wasn't implied), then the current in Q in (ii) would be greater than in (i).
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    (Original post by CD223)
    Sure. Can someone find Merhdad's answers to the MC? So we can debate them?


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    hey dude, how did you feel about the paper?
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    (Original post by Kennethm)
    hey dude, how did you feel about the paper?
    Not too bad to be honest. It was a fair paper, I just made a few silly errors. Only thing that angers me is the typo.


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    (Original post by JizzaStanger)
    Yes but it's the rate of change of flux that counts. If the current through P changed more quickly when the resistance was changed than when S was closed (unlikely but not impossible, the converse wasn't implied), then the current in Q in (ii) would be greater than in (i).
    The change in resistance wouldn't make the current go to 0 though, so it's likely the change in flux is less than in i.
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    (Original post by CD223)
    Not too bad to be honest. It was a fair paper, I just made a few silly errors. Only thing that angers me is the typo.


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    how did you answer the typo question?

    Yeah it was fair I guess, really annoyed at how i did in terms of the damping Q and the magnetic field qualitive. and I didnt do the 6 marker - must have taken like 1/2 marks from it maybe.
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    (Original post by CD223)
    Sure. Can someone find Merhdad's answers to the MC? So we can debate them?


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    Is that the exact username? I can't find the account to search the post history..
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    As I wrote lots of different marks to get the marks in some questions, some of my answers were not written on the dotted lines coz i didnt have enough space.
    Will the answers which are not on the dotted line be still marked ?
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    I really dont think so because wb is the unit for flux, not flux density
 
 
 
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