Test Tommorrow, Electric Fields

[Earn Success]

Homework Statement

Find the electric field for a point in the center of a square, +45microC on one corner and -27microC on the other 3

Homework Equations

E = (kQ1)/r²

The Attempt at a Solution

I know how to do the Electric field equations in a straight line, but for a square I'm not sure how to set it up. Also is the electric field always negative? Apparently it is in the direction of the force, but to find the force one must understand that the field repels negative charges and attracts positive, so I'm assuming it is negative.

 

[Sethric]

Field lines point away from positive charges, towards negative ones. So the field here will have a direction. When you were working with two charges on a straight line, you called it positive or negative and defined it as towards or away from something. Now it is a vector. Try drawing your square and drawing line segments from the center to the corners. How long are those line segments?

 

[NeedsHelp1212]

the test charge is assumed to be positive so its actually attracted to negative charges and repelled from positive charges. At least that is what my book says and what I learned. And do you have the length for one side of the square or I guess you can just make up a value? Because to find the distance from the center to one of the corners you can find the diagonal of the square and than divide by 2. Then find the electric field created by each point with the equation. Break everything down into components, combine, then use Pythagorean theorem to find the resultant electric field strength vector. That's the most I remember

 

[Earn Success]

.525

 

[NeedsHelp1212]

So the distance from the center to each corner is .371. I found the diagonal then divided by 2.

***Please help with my mutual inductance question!

 

[Earn Success]

So I found the electrical field for each of the four corners:

2.94 x 10⁶C for the 45microC charge and then

1.77 x 10⁶C for the 27microC charges

Now what do I do... I don't understand what the hell and electric field even is so I'm not sure what the directions are. And the answer is supposed to be 4.7x10⁶C, so I'm not going to get that no matter what I do with those answers. /Frustration

 

[NeedsHelp1212]

what corner has the 45 micro charge.

 

[Earn Success]

Wait actually the answer is correct if I just take the 2.94 and the 1.77 and add them together, then the other two diagonals cancel because they are of the same magnitude. Thanks for the help peoples, I live to fight another day of honors physics...