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    i got .521 as pd across 25 resistor is that rite?
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    (Original post by mackin boi)
    i got .521 as pd across 25 resistor is that rite?
    i'm afraid not

    it was 47kΩ n 25Ω....not just 47+25Ω
    the final answer came out as about 8*10^-4v
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    Mackin boi, Why dont you read through the thread before posting?
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    (Original post by sequence123)
    Mackin boi, Why dont you read through the thread before posting?
    v good point :rolleyes:
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    what did u guys do for that bit in the passage question..
    where u had to calculate th p.d between the ionosphere n Earth for a given electric field

    i assumed it was a uniform field n jus used E=v/d...getting an answer of 1.44*10^7V

    rings any bells?
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    yeh i got that as well
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    (Original post by sequence123)
    yeh i got that as well
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    (Original post by RMIM)
    I have a copy of the passage here.

    "when the holes are aligned, A is Zero, and the induced charge is the effectively zero"

    But did it not what the position when induced charge was maximum? So that would mean when there not overlappping?
    yeh when they're not overlapping the charge is maximum the earth plate had holes top left, bottom right i think...the rotating plate when u draw it should have holes top right, bottom left...That shows the holes are not aligned.
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    i wonder if anybody couldnt do the radius question due to not having a ruler
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    (Original post by DmAsTeR)
    yeh when they're not overlapping the charge is maximum the earth plate had holes top left, bottom right i think...the rotating plate when u draw it should have holes top right, bottom left...That shows the holes are not aligned.
    I just drew a super imposed image.
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    I answered all the questions, but didn't feel confident in most of them, but after the exam and comparing with classmates, it seems ok, the confusing thing about the lead thingy is what happens to the KE?
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    (Original post by hajira)
    what did u guys do for that bit in the passage question..
    where u had to calculate th p.d between the ionosphere n Earth for a given electric field

    i assumed it was a uniform field n jus used E=v/d...getting an answer of 1.44*10^7V

    rings any bells?
    it was a uniform field as the previous diagram was a sketch of a uniform field of the earth's surce and the ionosphere.

    answer was

    1.44x10^7

    for potential divider question, haj was right.
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    (Original post by RMIM)
    I just drew a super imposed image.
    yeah me2
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    (Original post by Valerio)
    I answered all the questions, but didn't feel confident in most of them, but after the exam and comparing with classmates, it seems ok, the confusing thing about the lead thingy is what happens to the KE?
    Well that was the point of the question. The K.E is converted to (Internal energy) heat! - that why the temp goes up.

    What was confusing was the questions after.

    1. Do you expect the real temp rise to be greater or less than the calculated value (well that not it but it was on those lines).

    Well first I though not all the K.E will be turned to heat. Some will be turned into sound. So I thought real value would be less.

    But then I thought of all the ball rubbing against each other. Heat due to friction so I change my mind. (But did write about the sound too).

    2. What would you expect if water was used (again not the real quesrion, but its on those lines)

    Anyway the heat capacity of water is much higher. i would expect the temp rise to be much less. But the question was worth 3marks! what the -
    I said some rubbish about there being more molecules than ball bearings, no idea what that means though.

    Stupid questions!
    Can someone tell us what we should have wrote. I think it was 3marks + 3 marks for the 2 questions.
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    Anyone feel like typing up answers with the marks next to them?
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    (Original post by sequence123)
    Anyone feel like typing up answers with the marks next to them?
    Damn it I knew I forgot something, I left my photographic memory at home!
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    (Original post by hajira)
    i'm afraid not

    it was 47kΩ n 25Ω....not just 47+25Ω
    the final answer came out as about 8*10^-4v
    ahh man im loosing marks all ovr the place for stupid things...
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    what does the earths electric field look like and why is it caused??
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    (Original post by sequence123)
    i wonder if anybody couldnt do the radius question due to not having a ruler
    What was that tip with the white paper? Hold it behind the ruler or something.
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    How did you measure the current of the two discs then? In the first question using the resistor and voltmeter where you had to draw a diagram
 
 
 
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