Ch 17/18 Electricity & Magnetism

Electric Charge:

Electric charge – a property of matter that creates electric and magnetic forces and interactions.

- can have a negative charge (-)- can have a positive charge (+)- can no charge (neutral)

Electric Charge:

- Like charges repel

- Opposite charges attract

Imbalance of protons and electrons

electric charge depends on an imbalance of protons and electrons.objects that lose electrons become

positively charged.

objects that gain electrons become negatively charged.

Chlorine gains an electron to become negatively

charged

Transfer of electric charge

when different materials are brought together electrons can be moved from one object to the other.

Flow of electronsConductor – something that

allows the flow of electronsEx.

Insulator – something that normally doesn’t allow the flow of electrons

Ex.

Charging objects:

Can charge an object by gaining or losing electrons

Charging objects:Ways for charging to happen:

1. Friction – Rubbing two materials against each other.- one becomes negatively charged and one becomes positively charged.

Charging by Friction

Charging objects:

Ways for charging to happen:

2. Contact – electrons move when you touch something

Inducing a ChargeWhen a neutral object is forced to

show a charge.when a charged object comes near a

neutral object it can cause the particles to arrange themselves so that the negative charges are arranged to be near the charged object, resulting in one part of the object having a positive charge and one part with a negative charge.

Charging an Electroscope by Induction

Electric Force

attraction or repulsion between charged objects

Electric Force

1. Amount of charge- strong charge = strong force

2 variables affect the amount of electric force.

2. Distance- closer the items = stronger force

Electric Field

area around a charged object where another object experiences the electric field

Electric Field

Can draw electric field lines to show the direction of an electric field and the strength of the charged object

Electric Currents

Electric Potential Energy

the PE of a charged particle due to its position in an electric field.

High PE when electrons are close

Low PE when electrons spread out

Voltage (volts)

Measurement of potential difference.

- the change in electric PE of a charged particle divided by its charge.

Currentthe rate that the electric charges move

through a given point (ex. a wire)

SI unit for current is ampere (A) 1 A = 1C/s

- 1C = 6.25 x 1018 electrons

Sources of electric current –

device that is a source of electric current because of the potential difference between terminals.

- ex.

2 types of electric current1. DC current

direct current- moves in one direction

- ex.

2 types of electric current2. AC current alternating current

- moves back and forth- ex.

Resistance

ratio of the voltage across a conductor to the current it carries.

R = voltage/current V/I SI unit = ohms (_______)

€

Ω

Resistance

occurs because of friction between the electrons in the current and the material in the conductor.

this friction causes heat and slowing the electrons

Resistance

amount of resistance is based on three variables

a. temperature- colder = low resistance- hot = high resistance

Resistance

amount of resistance is based on three variables

b. Length- shorter = low resistance- longer = high resistance

Resistance

amount of resistance is based on three variables

c. thickness- thicker = low resistance- thinner = high resistance

Circuitselectric circuit

- a device that creates a path for electric current to pass through.need a complete circuit for

electrons to pass through

http://phet.colorado.edu/en/simulation/circuit-construction-kit-ac-virtual-lab

Circuitsclosed circuit (no gap) = electricity

- open circuit ( a gap in circuit) = no electricity

- switch = device to open or close a circuit

- fuse = a device that prevents an overload of current

Closed vs. Open Circuit• Closed circuit oOpen circuit

CircuitsTwo types of circuits

1. series circuit- everything lined up on one circuit

2. parallel circuit- items lined up on parallel circuits