Electricity……EEElectricity

Electricity Chp 20

Electrostatics, the study of electric charges

The evidence of electricity has been noted since 2700 BC

Lets review some basics: Like charges repel Opposite charges attract An insulator is an object that a charge or

energy can not move easily through A conductor is an object that a charge or

energy can move easily through.

More Basics

The Atom Composed of Protons (+), Electrons (-) and

Neutrons Protons are found in the nucleus, along with

Neutrons. Electrons orbit the nucleus. In a neutral atom, the number of electrons

equals the number of protons Electric charges exert a force on other charges

at a distance This force is stronger when the charges are

closer together

Even More Basic Stuff

The charge possessed by a single electron and proton are equal at 1.60 x 10-19 C.

The magnitude of the charge on an electron is called the elementary charge

C = 1 Coulomb the SI unit for charge 1 Coulomb of charge is equal to 6.24 x

1018 electrons. A typical lightning bolt has 5 – 25 C A nickel can have up to 106 C of charge

balanced by positively charge protons.

Static Electricity

More Static Eelctricity

How?

Typically two non conductive or neutral objects in contact with each other will result in the transfer of electrons.

Air is non conductive but lightning and sparks fly across it. If the unbalance of electrons or protons is large enough, almost anything can become a conductor. In the case of air electrons are forced to move across it creating a plasma of charged atoms and freely moving electrons we see as lightning.

More charges

Electric charges can be move through induction or conduction.

Induced charges are charges brought on without physical contact. If a source of electrons or negative charge is brought next to two objects in contact the electrons will move from one to the other creating a positively charged object and a negatively charged one

More

Charging by conduction is where charges are brought by physical contact. A source of negative charge brought in contact with another object will transfer those excess electrons.

Charges will separate based on their polarity.

Electrostatic forces can be useful and destructive.

Charges?! We don’t need no stinking Charges.

As stated earlier. Force depends on distance and is the inverse square of the distance

F = 1/r2

Force depends on charge F = qa qb where q represents charge and (a) and (b) are charge if two objects

Coulombs Law

Coulomb was a French physicist around 1785 and established these relationships which are summarized in the following equation: F = K qaqb/ r2

Which states the force (F) between two objects (q) is equal to coulombs constant (K) times the product of the two charges (q) in Coulombs, divided by the square of the distance between them (r) in meters

K = 9.0 x 109 N – m2/C2

Remember this electric forces are vector quantities with magnitude and direction, sorry, more trig.

Lastly

We will play with Coulombs law tomorrow and the next day and the next day……