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Electricity homework

  1. Nov 3, 2008 #1
    1. The problem statement, all variables and given/known data
    Three questions in all. I am unable to find out HOW to get the answer with my text book.
    1. An insulator has a positive electric charge of 2.4 x 10^-17 C. How many electrons were added or removed? (^-17 means to the power of negative 17). The answer is 150 electrons removed. However, i am not sure how to get to this answer!

    2.If two protons are moved 3 times father apart, the electrical force between them is what factor of the original force? The answer is 1/9. Again, no idea how to get that.

    3.If two protons are moved 3 times closer together, the electrical force between them is what factor of the original force? Answer is 9 times greater... how? no idea.


    2. Relevant equations
    In my text book, i have the following info: which may be used to find the answer, but i dont know how.

    Electron------------Mass 9.11 x 10^-31kg-----------Charge -1.60 x 10^-19
    Proton-------------Mass 9.673 x 10V-27-------------Charge 1.60 x 10^-19


    3. The attempt at a solution

    I have tried dividing the charge by 3 and also divding by 3.. as the question suggests factor of 3.. but it obviously doesnt work.. im looking at some equations in the book.. some for current.. I=q/t.. but we have no "t" in these questions.. Pleae help!! I would greatly appreciate, as i have an exam tomorrow!! :)Thanks
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 3, 2008 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Re: Electricity

    Hi Jp_Garant! :smile:

    For 2 and 3, look up Coulomb's law
     
  4. Nov 3, 2008 #3
    Re: Electricity

    Thankyou Tim! I am now able to use this.. tho I needed help... simply because i didnt know how to apply the math. Thankyou :)
     
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