Electric Charges and Fields

Chapter Outline

Electric Charge
Conductors, Insulators, and Charging by Induction
Coulomb’s Law
Electric Field
Calculating Electric Fields of Charge Distributions
Electric Field Lines
Electric Dipoles
Chapter 1 Review

Figure 1.0.1. Electric charges exist all around us. They can cause objects to be repelled from each other or to be attracted to each other. (credit: modification of work by Sean McGrath)

Normally it is through the study of Newton’s laws, which govern the motions of everyday objects, that we first introduce students to the mathematical concept of force. Several physical phenomena can be identified as forces based on the effect they have on a physical object: Specifically, they cause objects to accelerate, to change their momentum. Thus, a force is recognised by the effect that it has on an object.

Gravitation, for example, is a phenomenon that is identified as a force that acts on all objects with mass. In this chapter, we begin the study of the electric force, which acts on all objects with a property called charge. The electric force is much stronger than gravity (in most systems where both appear), but it can be a force of attraction or a force of repulsion, which leads to very different effects on objects. The electric force helps bind atoms together, so it is of fundamental importance in matter. But it also governs most everyday interactions we deal with, from chemical interactions to biological processes.