physics question

[wlee43]

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Three equal and positive charges q are located equidistant from the origin
as shown in Figure 17.14. Is the direction of the electric fi eld at the origin
(a) along +x, (b) along -x, (c) along +y, or (d) along -y?

answer is D but why?

the picture is : on this site: concept check 17.4

http://books.google.com/books?id=Bw...ectric fi eld at the origin (a) along&f=false

 

[milski]

Three equal and positive charges q are located equidistant from the origin
as shown in Figure 17.14. Is the direction of the electric fi eld at the origin
(a) along x, (b) along x, (c) along y, or (d) along y?

answer is D but why?

Well, without the figure there is not much to be said.

 

[Ssina]

mm where is the picture?! is this TBR question?!

 

[milski]

The ones to the left and to the right are canceling each other's field at the origin - same distance, opposite direction. The one above it is positively charge, so the field is pointed away from it, which make it pointed downwards at the origin -> answer d.

 

[wlee43]

why do the EF on the X-axis cancel each other out? what if one is positive and the other is negative on the x-axis?

 

[milski]

That's exactly it - the one from the charge on the left is pointed to the right and is positive. The one from the charge on the right is pointed left and is negative. Since the charge and the distance are the same, the magnitudes are the same. So it becomes E + (-E) = 0

 

[wlee43]

And Im not assuming the origin isn't another positive charge correct? and its just a point in space

 

[Pisiform]

And Im not assuming the origin isn't another positive charge correct? and its just a point in space

no there is not.

 

[milski]

And Im not assuming the origin isn't another positive charge correct? and its just a point in space

Well, they say three charges - the origin does not have a charge on it.