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

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    (Original post by CD223)
    

\dfrac{8}{2} = \dfrac{x^2}{(60-x)^2}

    Where x is the distance to the 8nC charge.

    

\therefore 4 = \dfrac{x^2}{(60-x)^2}

    

\therefore 2 = \dfrac{x}{(60-x)}

    

\therefore 2(60-x) = x

    

\therefore 120 - 2x = x

    

\therefore 120 = 3x

    

\therefore 40 = x

    Does that help?


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    Thanks, get everything, how did you go about doing the first step, where you have 8/2.....?


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    (Original post by TeddyKC)
    Thank you!
    But I still don't quite understand, why are they roughly in phase if the frequency of the driver is much less than they natural frequency and vice versa for (iii) ?


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    No problem!

    Regarding your question: It's from Barton's Pendulum experiment.
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    Thank you very much. I don't know why I keep struggling with these questions.
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    predictions for the 6 marker??
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    can someone upload the esq's only for chapters 3 and 5 of unit 4 thanks
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    (Original post by Ilovemaths96)
    Big 6 mark questions of unit 4 paper

    i think last year was a designing a capacitor related expt

    june 13 - comparison between grav and electric fields
    jan 13 - satellites
    jun 12 - grav fields
    jan 12 - magnetic levitation (em induction)
    june 11 - principles of high voltage transmission systems and why is ac preferred (odd question imo)
    jan 11 - describe experiment to measure acceleration of havy cylinder, capacitor discharge circuit invovled
    jun 10 - dicussing conservation of energy and momentum when applied to explosion
    jan 10 - energy losses in a transformer

    June 2015? Maybe something shm related or electric field related?
    6 marker
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    (Original post by Jimmy20002012)
    Thanks, get everything, how did you go about doing the first step, where you have 8/2.....?


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    That's the ratio of the two charges


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    (Original post by Disney0702)
    Thank you very much. I don't know why I keep struggling with these questions.
    No worries!


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    Came across these questions over the weekend, anyone want to have a go at them? (Mehrdad and CCD, if these have come up already, can you let me know the page?) The paper is PHYA4 January 2013

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    The mark scheme for 2 a) (ii). for this question, don't need numerical advice, just a description of the thought process and the method taken to calculate the answer.
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    Can someone help me with following question please?

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    I thought the answer was A because the electron is parallel to the magnetic field but the answer is C and I do not understand why.

    Thank you in advance.
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    I have another question.

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    I do not understand how the answer is C.
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    (Original post by Disney0702)
    I have another question.

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    I do not understand how the answer is C.
    I had to look up myself but there u go

    http://www.thestudentroom.co.uk/show....php?t=2184551

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    Sorry quoted wrong

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    (Original post by Disney0702)
    I have another question.

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    I do not understand how the answer is C.
    Emf is rate of chanfe of flux.
    If u look at the grap above the gradient for flux linkage graph represents the emf induces. So steeper gradient higher induced emf. And vice versa

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    Thank you for that. But I'm afraid I still do not understand.

    Does it mean for a charged particle to move parallel to a magnrtic field it has be going in the same direction as the magnetic field?

    So in this question should the electron be moving parallel to the uniform magnetic field it'd have to be travelling south, right?
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    (Original post by Disney0702)
    Can someone help me with following question please?

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    I thought the answer was A because the electron is parallel to the magnetic field but the answer is C and I do not understand why.

    Thank you in advance.
    R u sure answer isnt A

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    (Original post by a.a.k)
    Emf is rate of chanfe of flux.
    If u look at the grap above the gradient for flux linkage graph represents the emf induces. So steeper gradient higher induced emf. And vice versa

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    Oh wow! Penny drop moment! Thank you very much.
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    (Original post by Disney0702)
    Can someone help me with following question please?

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    I thought the answer was A because the electron is parallel to the magnetic field but the answer is C and I do not understand why.

    Thank you in advance.
    The answer is A. Have you read the MS slightly wrong? Essentially the electron is parallel to the field lines so no magnetic force is experienced. Could you double check? Because I'm 95% sure it's A haha.


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    (Original post by CD223)
    The answer is A. Have you read the MS slightly wrong? Essentially the electron is parallel to the field lines so no magnetic force is experienced. Could you double check? Because I'm 95% sure it's A haha.


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    That is what i was thinkinf

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    (Original post by a.a.k)
    R u sure answer isnt A

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    Uh this is slightly embarassing but yes you're right.
    The answer is indeed A.

    I looked at the wrong part of the mark scheme.

    Im clearly having a bad day!

    Sorry to have wasted your time
 
 
 
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