CHAPTER 17 SECTION 1ELECTRIC CHARGE &

FORCEpp 585-592

•What are the different kinds of electric charge?

•How do materials become charged?

•What force is responsible for most everyday forces?

A. Charge and Force1. Electric charges ( ____ and ____) exert a

_________.

RULE OF CHARGES =

“_______________________________________________”

2. A force of ______________ exists between opposite charges ( ____ and ____ )…and a force of ____________ exists between particles/objects of the same charge.

3. Force depends on: CHARGE and DISTANCE

e- p+

FORCE

ATTRACTION e- p+

REPULSION

opposite charges attract…like charges repel

Opposite charges attract

Like charges

repel

B. Electric Fields:•Regions of force around charged particles/objects (+) or (-)

•Force is exerted on other charged particles/objects

•Force is strongest NEAR the charged particles/objects

•Field lines never cross one another

C. Static Electricity*The word static means: _______________

Static electricity:

•The movement of charges ( _________ ) from one object to another without further movement.

•A neutral object gets an electric charge when it either gains or loses __________

*Each atom gains/loses 1, 2, 3…electrons

-When the # of p+ > # of e- = _______________ (lost e-)

-When the # of p+ < # of e- = _______________ (gained e-)

not moving, stationary

electrons

electrons

POSITIVENEGATIVE

3 ways of charging an object

(becoming (+) or (-))

Illustration

Definition

Method

1. FRICTION:

e-

Two objects are rubbed together. One object loses e-, one object gains e-.

2. CONDUCTION:•Charging an object through direct contact (touching)

•e- move from one object to another

Conductors are materials which allow electrons to flow freely from atom to atom

(METALS, WATER)

Insulators are materials which DO NOT allow electrons to flow from atom to atom

(PLASTIC, RUBBER)

3. INDUCTION•NO CONTACT!

• electrons rearrange within a neutral object when a charged object approaches it.

• e- attract or repel (move within the neutral object)…

p+ do not move!!!

D. Materials used to study static electricity:

lose e- (become +) gain e- (become -)

Rabbit furGlass

Human hairSheep's woolHuman skin

PlasticsSilk

Rubber

ElectroscopeUsed to detect an

electric charge

•Leaves hang down when no charge

•Repel when have the same charge

•Electrons move into the leaves (-) or away from the leaves (+)

Electroscope Animations: Conduction vs. Induction

PITH BALL•Cork/foil, hangs from a string•Can be charged + or -, then moves freely and attracts or repels object

After drying cloths in the clothes dryer, you may notice they stick together. Explain this “static cling”. Will there be more “static cling” if all of the clothes in the dryer are of the same or different materials? Explain.