Electrostatics: parallel plates

[Bond03]

This is probably very basic to ask but it's something that's been bothering me.

If you have two parallel plates and the one on top is + and the one on the bottom is - then I understand that the electric field will point south (from the positive plate to the negative plate) but WHY would it point in that direction?

And also lets say a problem states that a charge is put inbetween these two parallel plates but the problem dosn't state if the charge is an electron or proton. How would you determine which direction the F is in? (F= Eq )

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[aevea]

Electric field lines pointing from positive to negative is just a convention...they'll always point in the direction that the electrostatic force would push a positive test charge.

If a problem doesn't tell you whether the charge is positive or negative, there's no direct way to know which way the force would push it.

 

[FutureScaresMe]

This is probably very basic to ask but it's something that's been bothering me.

If you have two parallel plates and the one on top is + and the one on the bottom is - then I understand that the electric field will point south (from the positive plate to the negative plate) but WHY would it point in that direction?

It's just standard to draw the force due to an E field in the direction a psitive point charge would feel.

And also lets say a problem states that a charge is put inbetween these two parallel plates but the problem dosn't state if the charge is an electron or proton. How would you determine which direction the F is in? (F= Eq )

You would only be able to calculate magnitude, unless you were given more information describing the path of the point charge's movement

Edit: beaten! Takes too long writing these on an iPhone