Find the electric field at the origin

  • #1
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Homework Statement


Given two charged particles:

1) 5x10^-9 C, (-.03 m, 0 m)
2) -20x10^-9 C (.04 m, .02 m)

find the electric field at the origin.


Homework Equations


F = (kQq)/r^2
E = (kQ)/r^2

The Attempt at a Solution



So I know since 1)'s charge is plus, its field vector is

[itex] ( (8.99x10^{-9}) (Q) ) / (.03)^2 [/itex] i hat, meaning its going to the right

I use arctan to find the angle between the origin and 2), it is 26.57 deg, and pathagorean theorem to find the distance r to be .045m

since 2) is - charged, its electric field is going away from the origin at 26.57 degrees.

[itex] ( (8.99x10^{-9}) (Q) ) / (.045)^2 [/itex]

Now I can break it down in to components, but how am I suppose to find Q, the charge of the origin?

If they gave me a value for the electric force between the origin and one of the particles I can find Q, but with this information I dont see any way I can find it?
 
Last edited:

Answers and Replies

  • #2
TSny
Homework Helper
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There is no charge at the origin. In the formula E = kQ/r2, Q is the charge that is producing the electric field. Each of the two charges that are given in the problem is producing electric field at the origin.
 
  • #3
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20
There is no charge at the origin. In the formula E = kQ/r2, Q is the charge that is producing the electric field. Each of the two charges that are given in the problem is producing electric field at the origin.
Thank you sir. I was wasting my time on this question for 2 hours already.. now my answer matches my books answer. TY.
 
  • #4
TSny
Homework Helper
Gold Member
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OK, good work.
 

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