Posted by
**Sandra** on
.

Given a square of sidelength a = 4 cm. We place a charged particle at each corner, three of them carry + 2 nC of charge and one carries the same amount of negative charge.

What is the magnitude of the electric field at the center of the square?

I read a previous post for a similar question, and tried to solve this question using the method that was given in response to that post.

I don't understand one thing, and I'm really confused about it.

When we're solving for the electric field at the center of the square, do we assume that there is a point charge located there? i.e. use Coulomb's law for the point charge and one of the charges at the corner? then mutiply the field found by that by 2.

Or would we find the electrostatic force acting on one charge, then use this charge to also find the electric field and mutilply this by 2?

Which is the correct way?