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

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    I'm thinking they have to scrap the 3 marks for the graph of the 300 Kohm question
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    (Original post by k9000)
    The last multiple choice question, did people put allows current to go to low resistivity sheath or structural reinforcement
    Structural reinforcement!

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    But it was oscillating left to right not spring oscillation so mass doesn't affect
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    (Original post by jf1994)
    Anyone else get 131 degrees for question 5a?
    yes
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    Did anyone else find that a fair few of those questions were from old spec/past papers
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    (Original post by emmalem2406)
    What did you put for the last MC question about the steel core?
    C but not sure
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    How did you guys calculate the electric potential energy?
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    (Original post by MSB47)
    I did a less steep graph because I thought with greater time constant it would discharge at a slower rate :/
    From what i've been told it's less steep
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    (Original post by Cmog)
    Did anyone else find that a fair few of those questions were from old spec/past papers
    Yep I was surprised
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    The question where we had to prove the capacotor was 30nC or something...can;t remember, just know I managed to get something like 28. something and it worked out to be 30nC to 1sf
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    anyone get 3400 vm-1 for one of the questions
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    (Original post by fruity97)
    But it wasn't a mass spring system was it?! I put that reason but crossed it out as I realised it's for a simple pendulum so mass doesn't even matter as it's just T=2pi root l/g
    Yeah, never mind, your answer's correct.
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    (Original post by MSB47)
    I did a less steep graph because I thought with greater time constant it would discharge at a slower rate :/
    I did a less steep graph with double the time consant at starting from the same current. Is that correct?
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    27.8 or 28nC so approx 30nc for q after graph in Electric fields q?
    Then for the next I did 1/0.2 and 1/0.5 and looked at the graph for change in V then multiplied by given 60nC to find work done.
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    (Original post by fruity97)
    Yes!! You have no idea how great it feels when even one person gets the same answer as you, I had no clue what I was doing just kept plugging numbers in! Did you get 2 revolutions per second as well?
    My heart dropped when I couldn't figure out how to convert to degrees! And yeah I did, if you're on about the breaking tension question? Great minds think alike
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    (Original post by annierox1863)
    rate of change of momentum is m(v-u)/t units are ms-1/s which makes ms-2 so acceleration surely
    Rate of change of momentum is force so unit is Newtons (kg Ms-2) you missed the KgTherefore it was D. weight
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    (Original post by Fvthoms)
    You might lose the mark for significant figures. Has to be 130 exactly.
    But they didn't state "to correct sf" like they did for the height of 1.4m one? Surely 131 degrees is allowed? !
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    (Original post by annierox1863)
    my answers i can remember
    forced vibration made by driving force and are in phase, amplitude smaller than at resonance
    resonance is at natural frequency and 90 out of phase amplitude large
    ring did affect the pendulum THIS IS WRONG THOUGH :-(
    RING DOESNT AFFECT DAMPING I DONT THINK
    coulombs law: force of two point charges is inversely proportional to the square of distance and proptional to the product of its charges
    3300 electric field strength
    no. of rotations 0.3 ?
    degress angle 2.2
    tension 12.34
    graph half the current at start then levels out to the same point as other curve
    6 mark
    Quote three laws, mention centripetal force and acceleration, velocity changes
    Not horizontal due to gravitaion force
    unit wb (flux linkage) 0.0608 ? not sure
    4.48v somthing for emf
    You put 2.2 for the degrees when it was 2.2 radians. You had to convert it to degrees i think i got 130 or something
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    (Original post by imyimy)
    27.8 or 28nC so approx 30nc for q after graph in Electric fields q?
    Then for the next I did 1/0.2 and 1/0.5 and looked at the graph for change in V then multiplied by given 60nC to find work done.
    I think I did this too, but did you get minus 27.8 for the charge? And then just discounted because it asks for magnitude?

    I think I got 4.5x10^-3 or something for work done by same method you used, and then 1xxx (19xx?) for electrical field strength, can't remember exactly.
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    (Original post by fruity97)
    But they didn't state "to correct sf" like they did for the height of 1.4m one? Surely 131 degrees is allowed? !
    Yeah allowed. Don't worry 3sf is acceptable.

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