p6 3.1

“Electric” comes from the Greek word __ (amber)

elektron

Around __, Greeks found that rubbing amber with wool made it attract light objects

600 BC

electrostatics

charges that stay still. One object becomes positive, the other becomes negative.

Benjamin Franklin

named the two charges.

Conductors

let charges move easily. Contain free electrons that flow inside. Examples: Metals, salty water.

Insulators

do not let charges move easily. Electrons are tightly bound to atoms. Examples: Glass, rubber, plastic

Charging by induction

▪ Charging without contact.

▪ A charged object brought near causes charge separation.

▪ One side becomes positive, the other negative.

▪ Separating the objects keeps each with opposite charge.

▪ No charge is lost from the charged rod.

Charging by contact

▪ A charged object touches a neutral one.

▪ Example: Positively charged glass rod touches an electroscope.

▪ Electroscope becomes positive; leaves spread apart.

polarization

▪ Happens when charges inside a neutral object shift slightly.

▪ One side becomes slightly positive, the other slightly negative

Coulomb’s law

▪ Describes the electrostatic force between two charged objects.

▪ The force gets weaker as the distance increases

Developed Coulomb’s Law

Charles-Agustin de Coulomb (1736–1806)

value of k

8.988x10⁹ Nm²/C²

value of electrons and protons

1.6x10⁻¹⁹ C

1μC

1×10⁻⁶

1mC

1×10⁻³

1nC

1×10⁻⁹

Social Science

Politics, Economics, History, Human Behavior

Applied Science

Medicine, Engineering, Architecture

Natural Science

Zoology, Botany, Microbiology, Physics, Chemistry, Astronomy

fusis or physikos

physics came from the greek word meaning natural

Classical Physics

Traditional topics before beginning of the 20th century. Matter and energy under normal conditions.

Mechanics optics acoustics thermodynamics electromagnetism

Modern physics

Concerned with the behavior of matter and energy under extreme conditions atomic or nuclear, relativistic, plasma ,quantum, solid state

Electric field

Charges can attract or repel without touching, this force works over a distance. The space around a charged object. Acharge object creates this which can influence other charges nearby.

Charges naturally move from

high to low potential

positive

glass rubbed with silk becomes

negative

plastic rubbed with fur becomes