The electric field equation is shown below. Before we get to it, ask yourself this question, " What is an electric field ? "
Therefore, many people may ask themselves this question, " How does the charged object know that the test charge is in the neighborhood ? "
We answer this question by saying that there is a force field, more specifically, an electric field in the space surrounding the charged object.
The electric field is however a vector field with more than one vector.
Use one vector for each charge around the charged object
An electric field will look like the graph you see below.
The electric field equation measures the force exerted on just 1 small test charge placed in the field.
Important observation about the first illustration above.
Nonetheless, when we thing about it deep enough, we will see that action at a distance can happen with iron filings and a magnet.
It is also happening with objects placed near the earth in space.
These objects will be in a gravitational field as they each experience the force of gravity.
The gravitational field around the earth is what keep a satellite in its orbit near the earth.
We can find another equation for the electric field by combining the following 2 equations.
F / q1
F = k
|q||q1| / d2