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Homework Help: Y-component of Electrostatic Force

  1. Feb 12, 2007 #1
    1. The problem statement, all variables and given/known data
    Calculate the X, Y, and magnitude force between the two charges. Compare to the computer simulation results.

    2. Relevant Equations
    Do not forget that this is a 2-D problem. Use the 2-D Coulomb’s law for line charges.

    3. The attempt at a solution
    Basically we used a software called MAXWELL to plot 2 charges, 1 source and 1 probe charge. The source had a charge of 1 x 10^-12 C and probe -1 x 10^-13 C. The source charge had a radius of 5mm, while the probe had a radius of 0.5mm and the distance between them (Centre to centre) is 10mm. Both charges lie on the x-axis.

    The software gave the following results,
    Fx = -1.8E-13
    Fy= 3.1E-16
    Fmag =1.8E-13

    I do know how to calculate the x-component, however I am confused on the y component. If both charges lie on the x-axis, wouldnt there only be an x-component of Force? How would I go about calculating it?

  2. jcsd
  3. Feb 12, 2007 #2
    Tired and probably wrong...

    Well, I'm very tired at the moment (late night doing EE homework!!) but offhand I would say you are correct, if both charges lie on the x-axis, the y component should be zero. It is possible that the result from your computer simulation is a "virtual" zero, i.e. errors in the calculation introduced from using a finite number of bits in base 2 means that the answer is not EXACTLY zero, but is extremely close... remember that your y-component that you found is 1/1000th of the X component (approx.) You can see this in matlab quite often as well, when an answer of say 1E-60 is considered a 0 in many situations. Sorry if I am totally off base here!

    Tristan Jones
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