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Homework Help: Electric Force and Field

  1. Sep 27, 2004 #1
    I was just doing my homework and i am stuck on this question. Can you please help me with this?

    a) Caluculate the electric field strength E, at a point located 3.0 cm due east from a point charge q=+1.0 microcoulomb.

    I know i have to use the formulas:
    E = F/q

    And Coulomb's law. But to use Coulomb's law you need to two charges and this question only has one. Please help on this, Thankyou.

  2. jcsd
  3. Sep 27, 2004 #2


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    If the force on q due to Q is
    [tex]\vec F = qQ \frac {\vec r}{r^3}[/tex]
    then the electric field due to Q is
    [tex]\vec E = Q \frac {\vec r}{r^3}[/tex]
  4. Sep 27, 2004 #3
    Am i right in saying:
    E = (k*Qsource) / (r^2)

    E=[(9*10^9)*(1.0*10^-6)] / (0.03)^2
    E= 1.0*10^7
  5. Sep 27, 2004 #4
    [tex]\vec E = Q \frac {\vec r}{r^3}[/tex]

    What is the vector r equal to and is the Q the point charge 1.0 microcoulomb that is given in the problem?
    I'm sorry i don't understand the equation completly, im still in year 11.
  6. Sep 27, 2004 #5


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    [itex]\vec r[/itex] is the displacement vector from charge Q to charge q.
  7. Oct 6, 2004 #6
    Thank you for your help!
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