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

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    (Original post by Mehrdad jafari)
    I think the current flowed from Y to C2 even though the electron flow was in the reverse direction.


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    Lol I'm now more confused than I was in the exam. I'm pretty sure I'm wrong. It's an equal split of opinion amongst my friends and classmates.

    Once you have the MS it will be interesting to see how it turns out. I can't make my mind up which I believe - I certainly don't think what I put was correct reasoning, even if I did tick the right box by fluke.


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    (Original post by CD223)
    All three options make sense to me. I don't dismiss any of them because all arguments have convincingly "correct" supporting evidence.

    I wasn't sure if it meant the instant that V2 was at a max or just after.


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    I definitely agree with you, all of then can be justified as the correct answers


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    (Original post by CD223)
    Lol I'm now more confused than I was in the exam. I'm pretty sure I'm wrong. It's an equal split of opinion amongst my friends and classmates.

    Once you have the MS it will be interesting to see how it turns out. I can't make my mind up which I believe - I certainly don't think what I put was correct reasoning, even if I did tick the right box by fluke.


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    Yeah, even I didn't know what i was doing during the exam and i realised it just a while ago


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    (Original post by Mehrdad jafari)
    Yeah, even I didn't know what i was doing during the exam and i realised it just a while ago


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    Haha. How come you have access to you MS by the way - do your teachers let you?

    Wish mine did


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    (Original post by Lau14)
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    Merci!


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    (Original post by CD223)
    Haha. How come you have access to you MS by the way - do your teachers let you?

    Wish mine did


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    No, a friend of mine has access to them and so he gives me


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    (Original post by Mehrdad jafari)
    I can understand you. In such a case the answer is already suggested to you, you only need to explain that. Which part of the first question did you have difficulty with?


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    It was this part!!
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    (Original post by Mehrdad jafari)
    No, a friend of mine has access to them and so he gives me


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    That's cool - it'd be interesting to see what the answers to the obscure questions were. Like how a thinner match stick would change the graph haha.


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    (Original post by CD223)
    

E =\dfrac{1}{2} CV^2

    As the capacitor stores half the energy supplied by the battery.

    

P =\dfrac{\Delta E}{\Delta t}

    

\Rightarrow P=\dfrac{CV^2}{2 \Delta t}
    Hmm that definitely makes sense, but then what is wrong with my derivation of P=CV^2/t?
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    (Original post by CD223)
    That's cool - it'd be interesting to see what the answers to the obscure questions were. Like how a thinner match stick would change the graph haha.


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    Yeah true. I think there was a similar question to that in EMPA june 14. I wrote the gradient is unaffected and only the Y intercept increases. And you?


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    (Original post by Somniare)
    Hmm that definitely makes sense, but then what is wrong with my derivation of P=CV^2/t?
    The capacitor stores half the energy of the supply. Your derivation assumes all the energy from the supply is stored by the capacitor, which isn't the case.


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    (Original post by Mehrdad jafari)
    Yeah true. I think there was a similar question to that in EMPA june 14. I wrote the gradient is unaffected and only the Y intercept increases. And you?


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    Again, not confident in my answer. I said the gradient of y against \frac{1}{x} would increase.

    That paper didn't go well in my opinion, although there's not much I can do now.


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    (Original post by CD223)
    The capacitor stores half the energy of the supply. Your derivation assumes all the energy from the supply is stored by the capacitor, which isn't the case.
    Ah of course, thank you!
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    (Original post by CD223)
    Again, not confident in my answer. I said the gradient of y against \frac{1}{x} would increase.

    That paper didn't go well in my opinion, although there's not much I can do now.


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    Neither am i. What was x again, sorry?


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    What did everyone put for the last question on the EMPA?
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    (Original post by Somniare)
    Ah of course, thank you!
    No problem! How's your revision going?


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    (Original post by Mehrdad jafari)
    Neither am i. What was x again, sorry?


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    It was a glass film of water of height y and width x.


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    (Original post by sam_97)
    What did everyone put for the last question on the EMPA?
    I did a very careless mistake when i had to divide sum of the uncertainties by the total of the values of R if it was, and then work out the half of that percentage uncertainty


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    (Original post by sam_97)
    What did everyone put for the last question on the EMPA?
    Is that the one with the water rising in a very thin tube?

    I calculated:

    The internal radius:
    r = 1.36 \times 10^{-3}m

    The % uncertainty in internal radius r = 2.97%

    You?
 
 
 
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