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Homework Help: Electrical Conductors and Insulators, help

  1. Nov 10, 2008 #1
    1. The problem statement, all variables and given/known data
    A balloon, initially neutral, is rubbed with fur until it acquires a net charge of -0.60nC. (a) Assuming that only electrons are transferred, were electrons removed from the balloon or added to it? (b) how many electrons were transferred?

    Net Charge = Q = -0.60 nC

    2. Relevant equations
    Electron Charge = qe = -1.602 x 10^-19 C
    *meaning the Charge in 1 Electron = qe

    1 nC = 10^-9 C

    3. The attempt at a solution
    (a) HELP I'm confused in problem a. My book says it is added but it doesn't have any explanation. :( I want to know when electrons are removed or added.

    (b) I tried this but I'm not sure if it is correct.
    - I converted nC to C for the given net charge:
    Q = (-0.60 nC)(10^-9C / 1 nC) = -6 x 10^-10 C or -6 EXP -10 C

    -I get the numbers of transferred electrons through this:
    No. of Electrons = (Q)(1 electron/qe)
    = (-6 EXP -10 C)(1 electron/-1.602 x 10^-19 C)​
    *cancel C unit​
    =3.75 x 10^9 electron or 3.75 EXP 9 electron

    is this correct? i'm confused because my classmates' answer is different compare to me.

    and by the way, this one doesn't have any relation with this problem, what does this mean:
    what is -g? It's not a variable. It is just given as it is. It also belong in the topic of Electrical Conductors and Insulators.

    Please help.
  2. jcsd
  3. Nov 10, 2008 #2
    To answer a) Initially the ballon was neutral. That means the net charge was 0 C. Then, after charging it, the balloon acquired a NEGATIVE charge. That means electrons were added. Reason ? Well, electrons have negative charge. It's as simple as that

  4. Nov 10, 2008 #3
    b) looks ok to me

    1.0-g, can you tell me more about where you read this ? What question in your book ? What example ?

  5. Nov 10, 2008 #4
    thanks for explaining problem a. I didn't figure it out. :)

    regarding 1.0-g:
    Suppose a 1.0-g nugget of pure gold has zero net charge. What would be its net charge after it has 1.0% of its electrons removed?

    In my understanding, that is in grams, but I wonder why it has negative sign..
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