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Homework Help: Units of Coulomb, trouble understanding the question

  1. Jul 23, 2011 #1
    1. The problem statement, all variables and given/known data
    Two charges, q1 = 4.9 e C and q2 = -3.6 e C are located 105nm apart, what is the size of the force between the two charges?


    2. Relevant equations

    F=kqq/r^2

    3. The attempt at a solution

    I did it according to the formula and I got the answer wrong, so I checked it using an online force calculator between charges, and it gave the same answer I initially got. I looked up what e C is, thinking maybe it's indicating something smaller than 1 C, and couldn't really find a graduation for that, what am I doing wrong? Is it meant to be multiplied by 1.6 x 10^-19?
     
  2. jcsd
  3. Jul 23, 2011 #2
    Actually [itex]q_1 = 4.9 e C[/itex] is somewhat incorrect. [itex]e = 1.6\times10^{-19}C[/itex] is the elementary charge and already contain the unit Coulomb. So it is as if [itex]q_1[/itex] has unit Coulomb-Coulomb.
     
  4. Jul 23, 2011 #3
    So does this mean that I have to multiply 4.9 by 1.6x10^-19?
     
  5. Jul 23, 2011 #4
    Nvm, problem(s) solved.
     
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