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Homework Help: Electric charge please help quickly

  1. Nov 20, 2007 #1
    1. A system of 1525 particles, all of which are electrons or protons, has a net charge of -5.456 x 10^-17. a) how many electrons are in the system? b) what is the mass of the system

    2. mass of electrons is 9.11 x 10^-31.
    charge of electron is 1.60 x 10^-19

    3. i have no clue, can someone help
  2. jcsd
  3. Nov 20, 2007 #2


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    Since there is a net negative charge, there must be excess electrons. Use the magnitude of the excess charge to determine how many excess electrons there are. Now the remainder of the particles must be equally split between electrons and proton. You know how many of each. Simple arithmetic from there.
  4. Nov 20, 2007 #3
    so do i divide the excess by the charge of an electon?
  5. Nov 20, 2007 #4
    anybody help please
  6. Nov 20, 2007 #5
    if they are equally split then that means the net force is zero.. which i don't think it is
  7. Nov 21, 2007 #6
    ok, found that there are 341 extra electrons which makes the total electrons to be 933. now how do u find the mass?
  8. Nov 21, 2007 #7


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    Find the number of protons. Then total mass = no. of protons*Mp + no.of electrons*Me
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