Static Electricity Chapter 20. Electric Force Section 20.1.

Static ElectricityChapter 20

Electric ForceSection 20.1

ElectrostaticsElectric Statics that can be

collected and held in one place.

Charged ObjectsObject that exhibits

electric interaction after rubbing is said to be charged◦Like charges: Repel

each other◦Opposite charges:

Attract each other◦Types of charge:

Matter contains both charges

A Microscopic View of ChargeAll objects contain

light, negatively charged particles◦Neutral object: positive

charge of nucleus equals the negative charge of surrounding electrons

◦Separation of charge: Occurs when two objects are rubbed together

Conductors and InsulatorsElectric

Conductor◦ Material that

allows charges to move easily

◦ Metals (ie: copper, iron, silver, gold)

Electric Insulator◦ Material through

which charge will not move easily

◦ Glass, dry wood, plastics, rubber, cloth, and dry air

Electric ForceSection 20.2

Forces on Charged Bodies There are two kinds of charges:

◦ Positive and Negative Charges exert forces on other charges at a

distance. The force is stronger when the charges are closer Like charges repel; opposite charges attract.

ElectroscopeDevice used to

determine charge.◦ Metal knob

connected by a metal stem to two thin, lightweight pieces of metal foil.

Charging by Conduction

Charging a neutral body by touching it with a charged body◦ Leaves spread apart it electroscope is

positive

Separation of Charge on Neutral Objects

Neutral object will have charges separate. ◦ Neutral object will be attracted to

the charged object.

Charging by InductionCharging an object without

touching ◦ Single object can be charged by

induction through grounding

Coulomb’s LawForce depends on

distance◦ F = 1/r2

Force depends on charge

◦ F= qAqB

Coulomb’s Law

◦ F= qAqB/ r2

Elementary Charge◦ Magnitude on electron:

1.60 X 10 -19 C◦ 1 C = 6.24 X 1018

electrons

Coulomb’s Law

Force in Newtons (N)

Coulomb’s constant: 9.0 X 109 Nm2/C2

Distance between ChargesIn Meters (m)

Charge in Coulombs (C) of object 1

Charge in Coulombs (C) of object 2

The End!