文档介绍：PP UZZLERUZZLER
Soft contact lenses fortable to
wear because they attract the proteins in
the wearer’s tears, incorporating the
complex molecules right into the lenses.
They e, in a sense, part of the
wearer. Some types of makeup exploit
this same attractive force to adhere to
the skin. What is the nature of this force?
(Charles D. Winters)
chapter
Electric Fields
Chapter Outline
Properties of Electric Charges Electric Field of a Continuous
Insulators and Conductors Charge Distribution
Coulomb’s Law Electric Field Lines
The Electric Field Motion of Charged Particles in a
Uniform Electric Field
708
Properties of Electric Charges 709
he ic force between charged particles is one of the fundamen-
tal forces of nature. We begin this chapter by describing some of the basic
Tproperties of electric forces. We then discuss Coulomb’s law, which is the fun-
damental law governing the force between any two charged particles. Next, we in-
troduce the concept of an electric field associated with a charge distribution and
describe its effect on other charged particles. We then show how to use
Coulomb’s law to calculate the electric field for a given charge distribution. We
conclude the chapter with a discussion of the motion of a charged particle in a
uniform electric field.
PROPERTIES OF ELECTRIC CHARGES
A number of simple experiments demonstrate the existence of electric forces and
charges. For example, after running b through your hair on a dry day, you
will find that b attracts bits of paper. The attractive force is often strong
enough to suspend the paper. The same effect occurs when materials such as glass
or rubber are rubbed with silk or fur.
Another simple experiment is to rub an inflated balloon with wool. The bal-
loon then adheres to a wall, often for hours. When materials behave in this way,
they are said to be electrified, or to have e electrically charged. You ca