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Homework Help: Polarized Atom - Charges (q?)

  1. Oct 12, 2009 #1
    Okay, since this is just a very small portion of my homework question, I'm not going to use the format provided. I hope this doesn't get deleted!

    At first, I thought i could just use q in the final answer since I don't know what q is, but what I have is:

    A polarized molecule with electrons on the left and protons on the left. It has an effective charge separation of 5nm, and the net force on the molecule is 0.

    How do I find the q (charge) for this problem? What do I need to know/how do I do it???

    Any help would be appreciated...

  2. jcsd
  3. Oct 12, 2009 #2


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    Staff: Mentor

    Welcome to the PF. Could you please state the problem as it is given to you? There is not enough information in your post to understand what the problem is asking. Also, there is a left-left typo in your post; you probably meant left-right separation, correct?
  4. Oct 12, 2009 #3
    Ok, here is the problem in its entirety (it's long): The article we read discusses the use of electric fields in treating cancer. Because cancer cells split apart fast than other cells, electric fields are able to apply that field to the cells and reduce the time it takes for them to split. That's the summary...
    it can be found at this link http://www.rife.de/files/electric_fields_as_cancer_treatment.pdf

    My question is stated:

    The article discusses the use of alternating 1-2 V/cm electric fields as a cancer treatment. Consider a constant, uniform electric field of 2 V/cm inside a cell. Imagine a polarized molecule with effective charge separation 5nm. You should note that the net force on the molecule is 0, although the molecule is under tension. Find the tension (force) in Newtons that acts to stretch the molecule. Note that a volt, V, is Nm/C)​

    The diagram shows the electrons on the left, and protons on the right (sorry if I messed that up earleir).

    What I did so far:

    for the LHS:
    qE - (kq2/r2)

    for RHS:
    (kq2/r2) - qE

    2*(qE - (kq2/r2)

    and I have all information except q.

    Any ideas?
  5. Oct 12, 2009 #4


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    Staff: Mentor

    Hmm. The article talks about forces up to 60pN, but I'm with you so far -- not sure how to come up with a value for q.
  6. Oct 12, 2009 #5
    When I asked my professor, all he said was:

    "A polarized molecule has an effective charge equal to an electron on one end and a proton on the other."

    But he made it sound in class like it would not just be the normal value for q.
    I AM LOST!
  7. Oct 12, 2009 #6


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    Staff: Mentor

    Hmm. Well, it's at least worth a try using just a single electron/proton charge value. If you use that, how close to the 60pN number do you get?
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