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

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    (Original post by CD223)
    I remember being stuck on that horrid question!


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    They can throw in some really nasty ones, I usually screw up on the electric/magnetic field ones (like that question). I remember one where you had to find a point P which was surrounded by 4 charges. and you had to use Pythagoras before using the right formula as 2 of them cancelled out.

    Which part do you tend to gain/lose the most marks in?
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    (Original post by TheRAG)
    They can throw in some really nasty ones, I usually screw up on the electric/magnetic field ones (like that question). I remember one where you had to find a point P which was surrounded by 4 charges. and you had to use Pythagoras before using the right formula as 2 of them cancelled out.

    Which part do you tend to gain/lose the most marks in?
    Ugh magnetic fields is also the bane of my life. I've yet to encounter that delightful sounding question :P


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    (Original post by CD223)
    Ugh magnetic fields is also the bane of my life. I've yet to encounter that delightful sounding question :P


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    It was June 2010 Q14
    Have fun when you get round to it
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    (Original post by TheRAG)
    It was June 2010 Q14
    Have fun when you get round to it
    Do you have tips for the electric/magnetic fields MC questions?


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    (Original post by CD223)
    I personally can see it being an SHM pendulum or mass spring experiment.


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    I have my doubts as the ISA is SHM heavy.
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    I've been going through the text book recently, been through all the topics but electric fields so far. The one concept I really can't understand is Back EMF and I don't really understand Lenz's law, although I've learnt it and am just hoping I am not asked to explain it haha.

    If anyone could shed some light on back EMF or lenz's law I'd appreciate it. Thanks.
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    (Original post by TheRAG)
    -224g because the wire is lifted off the scale (you have to assume that the scale only records a change in mass and not the actual mass) and the fact that when I doubles F doubles (hope this helps)
    pretty stupid question imo
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    (Original post by JJBinn)
    I've been going through the text book recently, been through all the topics but electric fields so far. The one concept I really can't understand is Back EMF and I don't really understand Lenz's law, although I've learnt it and am just hoping I am not asked to explain it haha.

    If anyone could shed some light on back EMF or lenz's law I'd appreciate it. Thanks.
    I will give it a go to see how well I understand it myself:
    If a wire (as part of a complete circuit) is moved in a magnetic field, its electrons experience a force.

    Lenz's law states that the induced emf will be in the direction as to oppose the change that caused it. This plays into the idea of conservation of energy.

    The energy used to move the conducting wire through the magnetic field which resists it is what produces the current. Since energy cannot be created or destroyed, the emf will be in a direction as to oppose the change that caused it.
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    (Original post by JaySP)
    I will give it a go to see how well I understand it myself:
    If a wire (as part of a complete circuit) is moved in a magnetic field, its electrons experience a force.

    Lenz's law states that the induced emf will be in the direction as to oppose the change that caused it. This plays into the idea of conservation of energy.

    The energy used to move the conducting wire through the magnetic field which resists it is what produces the current. Since energy cannot be created or destroyed, the emf will be in a direction as to oppose the change that caused it.
    Okay, you're getting at the conservation of energy. My understanding would be that work is done to move a conductor through a magnetic field and this must be equal to electrical energy created (so as to conserve energy)? (PD is work done per unit charge so the PD created may be proportional to the work done). If this is correct, you've prompted me to understand lenz's law because I assume that the current then must act in the opposite direction to the work being done? I don't really know still, just making random guesses based on what makes sense to me
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    (Original post by JaySP)
    I have my doubts as the ISA is SHM heavy.
    I would say it is more likely to be about transformers or magnetic fields personally.


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    (Original post by TheRAG)
    I don't have a copy as of yet, but will do soon hopefully. How are you finding A4 so far? What are your revision techniques/strategies etc?
    What it really boils down to is your puzzle solving abilities in all honesty. Practise well and stay calm during the paper. Maintain a clean thought process and really just think about what you're doing during the passed papers.

    Physicsandmathstutor (just google it) has some excellent resources on questions per topic to practise with. Just get hold of as many questions as you can and you get something wrong make sure you note down why even if it was a poor mistake (eg putting in the wrong value into an equation.)

    Happy practising!
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    (Original post by Kennethm)
    What it really boils down to is your puzzle solving abilities in all honesty. Practise well and stay calm during the paper. Maintain a clean thought process and really just think about what you're doing during the passed papers.

    Physicsandmathstutor (just google it) has some excellent resources on questions per topic to practise with. Just get hold of as many questions as you can and you get something wrong make sure you note down why even if it was a poor mistake (eg putting in the wrong value into an equation.)

    Happy practising!
    Thanks for the tips - very useful


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    (Original post by CD223)
    Thanks for the tips - very useful


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    http://www.physicsandmathstutor.com/...on/aqa-unit-4/

    Could you put this on the resources list?
    These were the questions I was referring to.

    And NP
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    (Original post by Kennethm)
    http://www.physicsandmathstutor.com/...on/aqa-unit-4/

    Could you put this on the resources list?
    These were the questions I was referring to.

    And NP
    Yeah will add them to the first post in a second good idea!


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    (Original post by CD223)
    AAA as well! Good luck


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    Thank you. Good luck to you too

    What other subjects do you do?
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    (Original post by Kennethm)
    http://www.physicsandmathstutor.com/...on/aqa-unit-4/

    Could you put this on the resources list?
    These were the questions I was referring to.

    And NP
    Added to the PHYA4 and PHYA5 threads


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    (Original post by Disney0702)
    Thank you. Good luck to you too

    What other subjects do you do?
    Thanks! I'll need it

    As well as physics, I do maths, computing and history. You?


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    Does anyone have any of their own revision notes for this unit they would be happy to contribute to the thread?

    I'm in the process of finalising mine before I upload them onto here and the PHYA5 thread! Just trying to gather as many resources as I can for the benefit of everyone here.


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    (Original post by CD223)
    Thanks! I'll need it

    As well as physics, I do maths, computing and history. You?


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    Ah don't worry you'll be fine

    As well as Physics, I do Maths and Chemistry.

    I did English Literature last year, I loved it, but I knew I wouldn't have been able to invest much time into it as I would always prioritise Maths and Science. So I dropped it.
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    (Original post by Disney0702)
    Ah don't worry you'll be fine

    As well as Physics, I do Maths and Chemistry.

    I did English Literature last year, I loved it, but I knew I wouldn't have been able to invest much time into it as I would always prioritise Maths and Science. So I dropped it.
    Ah I hope you're right!

    Oh nice! Yeah essays for history are too much tbh - should have dropped it!
 
 
 
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