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Electric Fields problem: Can someone please check my work?

  1. Jun 10, 2015 #1
    "a +4nC charge is 6/0 cm along a horizontal line toward the right of a -3nC charged object. Determine the E field at a point 4.0 cm to the left of the negative charge."

    From what I understand, it goes Point ___ 4cm ____ (-3nC) _____ 6cm ____ (+4nC)

    Using that, I got the answer to be -14.75 nC but I'm very unsure of myself. Can someone check?
     
  2. jcsd
  3. Jun 10, 2015 #2

    SammyS

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    Hello goooogle. Welcome to PF !

    You have the layout correct.

    Can you explain how you got that answer?

    For sure, the units are not correct.
     
  4. Jun 10, 2015 #3
    Well, I did

    ((K)(-3 x10^-9))/(.04^2) + ((K)(4x10^-9)/(.1^2) which gets me -13275. From there, I did -13725 = ((K)(X))/(.1^2) which comes out to -14.75 nano coloumbs.

    Is that right? Is .1 the right distance for the second part?
     
  5. Jun 10, 2015 #4

    SammyS

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    For the first part: What is the direction of the E-field due to the negative charge? What is the direction of the E-field due to the positive charge?

    What are the units of the number -13275 ?


    What second part. You didn't mention a second part in the question.
     
  6. Jun 10, 2015 #5
    The direction for the E-field because of the negative charge would be to the right, so +? In that case, it'd be 16875 - 3600, which is +13275. So I understand that, I think. The units are N/C. The second part was just desperation, trying to find a step I missed.

    So I take it +13275 N/C is my final answer?
     
  7. Jun 10, 2015 #6

    gneill

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    Your result looks okay for magnitude, units, and direction. Be sure to round any result that is to be presented as a final answer to the correct number of significant figures.
     
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