Electric Fields

The Electric Field

We can describe the electric force on a charge q as the result of an electric field, E,

F = E q

Consider the force on a small "test charge" in the neighborhood of a positive charge Q.

Move the small "test charge" q around and investigate the force F that it experiences at different places near Q.

We will find an electric field originating on a positive charge.

Likewise, we will find an electric field terminating on a negative charge.

Electric Field Due to a Point Charge

Remember that the electric force is given by Coulomb's Law,

This electric force F can also be described in terms of the electric field E,


The electric field E due to a point charge Q is given by

Remember, the electric field E is still a vector!

What is the electric field a distance of 1 m from a positive charge of 1 C?

Numerical Example


Coulomb's Law

E-Field of Continuous Charge Distributions

Return to Ch23 ToC

(c) Doug Davis, 2002; all rights reserved