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EDEXCEL A2 Physics EXAM Unit 4 Physics On The Move 20th June 2016 (NOT I-A-L) Watch

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    (Original post by [email protected]$$)
    **** i got 83% for percentage decrease in charge
    take that from 100= 16.7 you lost one mark
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    (Original post by Mustafa347)
    i changed the multiple choice sphere charge question at the last second. I circled double both charges because i remember doing a past paper question where one of the charges was halved but angle of point charge remained the same. Therefore had no effect on the force. Had to be both
    nope its definitely halve just one man
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    (Original post by Freddielow)
    nope its definitely halve just one man
    Surely it did, if you halved the charge on both the force would be F/4 not F/2

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    For multiple choice was it 0.37 or 0.63? I think I may have misread question.
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    (Original post by Salty carpet)
    I put higher value...
    Its lower as V=angular velocity x radius and not fully inflater tyre means radius is smaller
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    (Original post by target21859)
    For multiple choice was it 0.37 or 0.63? I think I may have misread question.
    it was 0.37
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    (Original post by Freddielow)
    it was 0.37
    Yay that's what I got . And is it 17% or 33%? There is so much confusion.
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    (Original post by target21859)
    Yay that's what I got . And is it 17% or 33%? There is so much confusion.
    Personally i got 16.7, but not too confident
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    (Original post by target21859)
    For multiple choice was it 0.37 or 0.63? I think I may have misread question.
    0.37, it said "remaining charge".
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    For the question about the magnetic accelerating upwards away from the coil. When the questionasked you why the magnitude of current changes. Did you say it increased because rate of change of flux linkage increases since speed is increasing. Or it decreased as B decreases since the magnet is moving away


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    (Original post by oShahpo)
    0.37, it said "remaining charge".
    An good thought it said the opposite. Was 0.024 an answer as well?
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    (Original post by target21859)
    An good thought it said the opposite. Was 0.024 an answer as well?
    I got 0.024 as one of the multiple choice answers
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    (Original post by crimson1234)
    For the question about the magnetic accelerating upwards away from the coil. When the questionasked you why the magnitude of current changes. Did you say it increased because rate of change of flux linkage increases since speed is increasing. Or it decreased as B decreases since the magnet is moving away


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    I talked about the rate of change of flux linkage increasing as it was accelerating upwards, so Faraday's law states the induced emf increases and so does the current -- is that similar to what you wrote?
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    I think it's time for me to stop worrying about unit 4 and concentrate on S2/FP3/Unit 5 just two more days of exams
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    (Original post by crimson1234)
    For the question about the magnetic accelerating upwards away from the coil. When the questionasked you why the magnitude of current changes. Did you say it increased because rate of change of flux linkage increases since speed is increasing. Or it decreased as B decreases since the magnet is moving away


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    I said it decreased as the flux linkage decreases as the magnet moves away from the coil
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    (Original post by funkyfig)
    I talked about the rate of change of flux linkage increasing as it was accelerating upwards, so Faraday's law states the induced emf increases and so does the current -- is that similar to what you wrote?
    Yeah that's what I wrote but a few people in my class said flux density decreases as the magnet moves away so flux linkage decreases and so current decreases


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    (Original post by target21859)
    I think it's time for me to stop worrying about unit 4 and concentrate on S2/FP3/Unit 5 just two more days of exams
    Unit 5 is in one week, not two more days
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    (Original post by Qcomber)
    Unit 5 is in one week, not two more days
    I know I meant have 2 days left in which I have exams a week from now.
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    (Original post by crimson1234)
    Yeah that's what I wrote but a few people in my class said flux density decreases as the magnet moves away so flux linkage decreases and so current decreases


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    The actual magnitude of flux density is irrelevant, it's its rate of change that induces the EMF. Your answer is correct, although I missed the word accelerate, I said the velocity varies, bloody keywords.
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    (Original post by tkjoption)
    You are correct if the question implicitly says starting from the initial position
    but the question as I remembered, was
    it says it can be the allowed difference of silicon from its position is 0.7 mm
    meaning +/- 0.7 mm from the position is all possible i.e Maximum possible d is 3.5+0.7 minimum possible d is 3.5-0.7
    hence Dmax=4.2 mm
    Dmin=2.8 mm
    Question ask the maximum possible allowed percentage decrease
    so as maximum possible d is 4.2
    minimum possible d is 2.8
    the maximum possible allowed decrease is from 4.2 mm
    to 2.8 mm as
    it could be at 4.2 but is at 2.8
    hence max percentage decrease is 33.3%

    nevertheless I actually do understand your point , it is valid and logical from your prospective but

    but this does not mean that you start from 3.5
    Yeah I was 100% convinced it was 17% but now I'm not so sure, there's no denying that if you're at 2.8mm you could go to 4.2 which would be a 33% decrease like you say. Hopefully Edexcel will accept either because of the ambiguity of the question. I did all the working for 33% then crossed it out and did it for 17%
 
 
 
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