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Thread: charge

  1. #1 charge 
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    A positively charged strip is brought near a strip placed in a stirrup which is free to turn. There is a force of attraction. Which of the following could be true about the strip in the stirrup?

    i. it is uncharged
    ii. it has a negative charge
    iii. it has a positive charge


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  3. #2 Re: charge 
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by european SENS
    A positively charged strip is brought near a strip placed in a stirrup which is free to turn. There is a force of attraction. Which of the following could be true about the strip in the stirrup?

    i. it is uncharged
    ii. it has a negative charge
    iii. it has a positive charge

    I'd say i. and ii.


    Where did this question come from?


    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  4. #3  
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    A test I got back. Me and a teacher had a disagreement about the answer. I said it could be multiple and she informed me that there is only one correct answer. I wanted to get an oppinion before I went and argued with her though.
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  5. #4  
    Forum Masters Degree bit4bit's Avatar
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    ii.
    Chance favours the prepared mind.
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  6. #5  
    Forum Ph.D. william's Avatar
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    Oh.

    Well, maybe I'm not imagining the setup correctly, but answer ii. seems obvious. I also include i. if a local charge can be induced on the strip in question. This will happen if it is conductive.


    Cheers
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  7. #6  
    Forum Masters Degree thyristor's Avatar
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    I agree with william. And it's actually not so hard to induce a charge in a conductor. There's an electricty machine which I think is called Wilson's machine that uses this to create sparks of several feet.
    373 13231-mbm-13231 373
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  8. #7  
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    say im a junior in highshool, would such an explination that it is 1 and 2 be too advanced for me. im just in a normal physics class
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  9. #8  
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by european SENS
    say im a junior in highshool, would such an explination that it is 1 and 2 be too advanced for me. im just in a normal physics class

    Well, I assume the teacher says ii. is the answer and i. is in question.

    Does your teacher have a Van de Graaff generator?
    If so, take a small piece of tin foil, ball it up around some thread so you have a ball about 1 cm in diameter dangling from the thread.

    Hold the ball in your hand so as to ground it (make it neutral).

    Turn on the generator, and while holding the thread, bring the (neutral) ball of tin foil near the generator (but don't let the ball touch the generator).

    Watch what happens. (And keep in mind that the ball of tin foil is neutral, simulating part i. of this question.)


    You could propose this experiment to your teacher.


    Cheers
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  10. #9  
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    yes i believe we do have one of those. i will propose this experiment to my teacher. thank you mr william.
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  11. #10  
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by european SENS
    yes i believe we do have one of those. i will propose this experiment to my teacher. thank you mr william.

    You're very welcome.
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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