# Square array (electric field question)

## Homework Statement

Four charges q1 = q3 = -q and q2 = q4 = +q, where q = 6 µC, are fixed at the corners of a square with sides a = 1.3 m. (see attached .gif)

Calculate the x- and y-components of the net electric field at the midpoint M of the bottom side of the square.

## Homework Equations

Why dont the charges cancel in the field??
The distances and angles, are all equal
The charges are opposite.

SO how can there be a net electric field at that point (M)?

## Homework Statement

havent calc'd anything cause i dont get why field shouldnt be zero

## Homework Equations

im totally stuck
thanks for any help sum1.

## The Attempt at a Solution

#### Attachments

• showme2.gif
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If you were asked to find the field in the middle of the square, then you'd be correct: The field would be zero.

But not at point M. Note that on one side of M there's a +q and on the other side there's a -q. They don't cancel! (If M were in between two similar charges, then you could say that their field cancels.)

robphy