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Math Help - calculate the net charge.

  1. #1
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    calculate the net charge.

    A metal sphere has a charge of +7.0 C. What is the net charge after 8.00 1013 electrons have been placed on it?
    in C

    anyone able to help me with this one please.
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  2. #2
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    Quote Originally Posted by rcmango View Post
    A metal sphere has a charge of +7.0 C. What is the net charge after 8.00 1013 electrons have been placed on it?
    in C

    anyone able to help me with this one please.
    You mean 8.00 x 10^13 electrons?

    Well the charge of a single electron is -1.6 x 10^-19 C. So 8 x 10^13 electrons has a charge of...

    -Dan
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  3. #3
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    Quote Originally Posted by rcmango View Post
    A metal sphere has a charge of +7.0 C. What is the net charge after 8.00 1013 electrons have been placed on it?
    in C

    anyone able to help me with this one please.
    Well here's a start: How many coulomb is 8.00 1013 electrons? (You might need to refer to your class notes for the conversion). This NEGATIVE charge is added to +7.0 C.
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  4. #4
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    Quote Originally Posted by topsquark View Post
    You mean 8.00 x 10^13 electrons?

    Well the charge of a single electron is -1.6 x 10^-19 C. So 8 x 10^13 electrons has a charge of...

    -Dan

    So couldn't be just -1.6 x 1^-19 C * 8 x 10^13?

    then add that to 7uC?

    i'm getting confused from sig figs i think.
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  5. #5
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    Quote Originally Posted by rcmango View Post
    So couldn't be just -1.6 x 1^-19 C * 8 x 10^13? Mr F says: Yes.

    then add that to 7uC? Mr F says: Yes.

    i'm getting confused from sig figs i think. Mr F says: You wouldn't be the first.
    ..
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  6. #6
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    thanks got it, -5.72 uC
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  7. #7
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    Still need helpI'm working on the same problem

    Except I have
    A metal sphere has a charge of +8.0 C. What is the net charge after 8.00 x 10^13 electrons have been placed on it

    Everytime I try doing

    (-1.6x10^-19) x (8.00x10^13) + 8 = 7.9999872

    But thats not the correct answer.

    Why is that not working???
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