Charged rods

  1. tony873004

    tony873004 1,555
    Science Advisor
    Gold Member

    A negatively charged rod is brought near a suspended object, which is repelled by the rod.
    The suspended object then must be :

    a) positively charged
    b) negatively charged
    c) uncharged
    d) not enough info

    negativly charged is correct


    A negatively charged rod is brought near a suspended object, which is attracted to the rod.
    The suspended object then must be

    A) positively charged
    B) negatively charged
    C) uncharged
    D) not enough info

    Seems to me it should be A. But A and C are wrong.

    Could it be B? If it was negatively charged, they'd repel rather than attract.

    Could it be D? Not enough info? What else would I need to know?
     
  2. jcsd
  3. Astronuc

    Staff: Mentor

    Opposite charges attract, so a negatively charged rod would 'attract' a positive charge.

    Why did you say A (positively charged) is wrong?
     
  4. nazzard

    nazzard 100
    Gold Member

    Hello tony,

    maybe the question is meant to be a bit picky and they'd say it would be attracted due to gravitational force alone as well.:confused: Just a thought.

    Regards,

    nazzard
     
  5. tony873004

    tony873004 1,555
    Science Advisor
    Gold Member

    The online grading system said it was wrong. A was my first guess for the reasons you stated. Did the online grading system get it wrong? (wouldn't be the first time), or am I missing something?
     
  6. I suspect it would be D, not enough info. The answer could be either A or C... A because opposites attract and C because if the suspended object carried no nett charge then bringing a charged object near would induce a charge so the side of the object near your negative rod would be positive while the far side would be negative.
     
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