the net amount of electric charge produced in any process is zero

( aka if a postive charge is present then there is a negative charge nearby that is of equal magnitude)

 Structure of Atom

1.Nucleus :

protons & neurtrons

small

massive density

+ charge

2.Electron cloud

large

very low density

 - charge

 a molecule that is neutral overall,

but charge not evenly distributed

(e.g. water,

oxygen is more electronegative than hydrogen and excerts a stronger pull on the electrons).

leak off to water particles in the air b/c its polar.

(e.g. a neg charge off a ruler goes to the postive charge of the water particles in the air)

material in which the valence electrons can move freely within the material*

(note these e- can't leave easily)

(move quickly toward + objects, repel -  objects)

e.g. metals

Insulator def

Almost no charge flows

Most other materials

semiconductors def

1.start with a neutral metal rod

2.Bring a charged metal ball(ex it's +)close so that they touch

3. metal rod acquires that (+) charge

aka it acquires a charge b/c the objects are in contact

=

leaves both objects with SAME charge

Explain how Metal objects can be charged by

induction

1. start with a neutral metal rod

2.Now bring a (+) charged object close to the rod but NO touching.

3. The charges  within the rod are seperated (-)charges move to the end closest the (+) object and the other end (away from the object is now (+) charged.

the rod looks like:

(object) +©             ---           +++

* the charges in the rod have been seperated (no net charge created)

1.induction causes an object

2.conduction causes object

1. both objects to have opposite charges. Causes the neutral object to seperate its charges(0ne end is + the other is -)

Object is brought close but doesn't touch.

2. both objects to have the same charge by   physical contact.

 the electric force between 2 charges is :

proportional to (1)

inversely proportional to (1)

1. product of the charges

↑#, ↑Electric Force

2. distance between them.

↑distance, ↓Electric Force

(aka 2 far apart objects)

an equation gives the magnitude of the force.

F12 means

F21 means

 F12= the force felt by 1 caused by 2.

F21= the force felt by 2 caused by 1.

for multiple point charges,

the forces on each charge from every other charge can be calculated

and then added as vectors.

(aka the net force on a charge )

electric field def

give formula to help with definition

the electric field at any point in space is defined as the force, F, excerted on a tiny positive (+)   test charge placed at that point divided by the magnitude of that test charge.

E= F/q

true,

again the net electric field = sum of vectors

a small positive test charge is placed in the field, the direction is determined by how  the electric field behaves.

(electric fields radiates away from +

goes toward - charges)

 Start: with a positive charge (+)

End:on a negative (-) charge.

two equal charges, opposite in sign:

constant

(for ex a capacitor)

The magnitude of the field is proportional to the _______

(with respect to the field lines)

0

=

allows charges to move

The electric field is _____to the surface of a conductor, why? 

to the total number of field lines crossing the area

(proportional relationship)

↑field lines =↑ flux

what is Gauss’s Law?

The net number of field lines through the surface is proportional to:

1.the charge enclosed

2.flux

0

b/c cos (90)=0

increases

+ -

decreases

+-

(aka for visual purposes they will stick)

decreases

++

(by moving apart they are reducing repulsion energy)