Calculate charge on a body(in Coulombs)

  1. All right i have a simple problem but i just want to verify my results, so any help would be greatly appreciated. The problem is as follows:

    7.1* 10^12 electrons are added to a body that already has a negative charge of 0.2uC(the u is micro 10^-6). Calculate the final charge on this body.

    Now i have
    (7.1* 10^12)(1.602* 10^-19) + (0.2* 10^-6)

    which gave me 1.337 uC

    is this correct?
  2. jcsd
  3. whoops, i think it should have been:

    (7.1* 10^12)(- 1.602* 10^-19) + (0.2* 10^-6)

    which gave me 0.937 uC

    now im lost...please help.
  4. new info, 1C is equal to 6.24* 10^18 electrons
  5. ok, formula should be:

    (7.1* 10^12)/(6.24* 10^18) + (0.2*10^-6)

    = 1.337 uC which is the same as the first result i got...... 0_o
    i am going to go with this one.

    is this correct?
  6. enigma

    enigma 1,809
    Staff Emeritus
    Science Advisor
    Gold Member

    Check all of your negative signs. The problem states that the body already has a negative charge,

    Your magnitude looks right, but the sign is wrong.

    [mod hat]
    Moving the thread to homework help.
    [/mod hat]
  7. Thanks you were right about the sign, it was supposed to be -1.337 uC

    Also, sorry about the location of my topic i only put it there because the course i am taking is electrical engineering and there was a section that matched exactly. I just joined the forum and i already know i will be here every day to read up on the info i need. Thanks again for the help, i will keep all homework related problems here.
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