Chapter 6 – Electricity

6.1 Electric ChargePositive and Negative Charges• Matter is composed of _______• Atoms are composed of protons, neutrons and

electrons• The amount of positive charge on a proton is _____

to the amount of negative charge on an electron• Atoms have _______________ (electrically neutral)• Amount of electric charge is measured in ________

(C)6,250 million billion protons in 1 C of electric charge6,250 million billion electrons in -1 C of electric charge

Coulomb's Law: Like charges _____ and opposite charges _______.

Atoms

equal

no electric chargecoulombs

repelattract

• The difference between the # of protons and the # of electrons determines an object’s ___________; therefore(-) charged obj. have ______ electrons.(+) charged obj. have ______electrons.Obj. are charged by the _______of

electrons.

electric charge

morefewer

transfer

Transferring Charge• Electrons are

_______________ to some atoms and molecules than others

• Some atoms can _______electrons more easily than others

• Leads to an buildup of electrons on other substances (excess negative charge) _____________

bound more tightly

transfer

Static electricity

STAT

IC E

LECT

RICI

TY

Law of Conservation of Charge

Charge can be _________ from object to object, but it _______ be _______or _________

transferredcannot created destroyed

Charges Exert ForceThe force between electric charges depends on• ________between charges• ________of charge• _____

DistanceAmountMass

_______________ have similar properties.On this scale gravity dominates!

Gravitational Forces

Comparing Electric Forces and Gravitational Forces• Force of gravity is much ______ than

electric force– Electric force between a proton and an

electron in a hydrogen atom is about a thousand trillion trillion trillion times larger (1039 X) than the gravitational force between the same particles.

• Chemical bonds in molecules are due to _______ forces between atoms–Much larger than the ___________ forces

between the atoms

weaker

electricalgravitational

On this scale ___________ dominates!electrical force

Electric Fields• Surround every electric charge and exerts the

force that causes other electric charges to be _________ or ________.

• Do not need to be ________ to exert force on each other

• Any charge that is placed in an electric field will be ______ or _______ by the field

Electric Field Near Negative Charge Electric Field Near Negative Charge

attractedrepelled

touching

pushed pulled

Conductors and Insulators

Conductor• Material through which ____________________• Best electrical conductors are ________• Conductors have _____ resistance?

Insulator• Material in which electrons are ____________________• Electrons are held ______________ that make up

insulators• Best insulators are _____ , ______ , ______ and

________.• Insulators have a _____ resistance

electrons move easilymetals

low

not able to move easilytightly to atoms

glassplasticrubberceramic

high

Conductors and Insulators

Types of ChargingCharging by Contact

The process of transferring charge by _________ or ________.• Also called charging

by ___________

Charging by Induction

The _______________ of electrons on a _________ object caused by a _______ object

touchingrubbing

conduction

rearrangementneutral

nearby

Lightning

6.1 Summary• 2 types of electric charges are (+) & (-).

• Like charges repel, unlike charges attract.

• On molecular level, electric force is stronger than gravitational force

• Electric force acts through electric fields.

• Electric fields surround charged objects. Any charged object that enters a region with an electric field experiences an electric force.

• Electrons move easily through conductors

• Electrons do not move easily through insulators

6.2 Electric CurrentCurrent and Voltage Difference• ________________: the net movement of electric

charges in a single direction• Measured in _________ (A)• 1 ampere = __________________________ • A voltage causes charges to move, which in turn

produces a _______.• A circuit must be ______ for a current to be produced.

Electric current

amperes1 Coulomb of electric charge

currentclosed

A charged object has electric PE due to its position in an electric field.

Potential difference or ________ is the difference in electrical PE per unit charge.– SI unit for pot. diff.

(V) = volts = 1Joule/coulomb

– Ex. 12V vs. 9V

voltage

• Electric current is from _____ voltage to _____voltage

• Voltage difference is related to the _____________________________

• Voltage difference is measured in _____ (V)

_ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ __ _ _ _

_ _ _ _ _ _ _ _ _ _ _ _

Charge Flow

Current

Low Voltage High Voltage

higher

lower

force that causes electric charges to flow

volts

• ___________: a closed path that electric current follows

Electric circuit

Current and Flow DirectionThe _______ of the electric current is always from a _____ voltage to a _____ voltage, but …• The _______ in a _____actually flow from

a _____ voltage to a _____ voltage

direction

higher lower

electrons circuitlower higher

Batterieshttps://www.youtube.com/watch?v=CX84l5ZZHVgDry – Cell

Batteries• Consist of ___________

surrounded by a material called an ___________

• Electrolyte enables ________ to move from one electrode to another

• _________________ occurs when the 2 terminals are connected in a ________.

• ________ difference between these 2 terminals causes a current through a ____________.

• Example: _______________

Wet – Cell Batteries• Contains

_________________ made of different _______ or _________ compounds in an ___________

• The electrolyte is a ____________________

• Example: __________

2 electrodes

electrolytecharges

Chemical reaction

circuitVoltage

Closed ciruitFlashlight battery

2 Connected platesmetals

metallicelectrolyte

conducting liquid solution

Car battery

Dry - Cell Wet - Cell

Anode (negative)Cathode (positive )

Resistance• ___________: the tendency for a material

to resist the flow of electrons and to convert electrical energy into other forms of energy–Measured in ohms ( )

• Caused by _____________ which slows the movement of ____________________________

• Resistor: ______________ _______________________ ______________________

Resistance

internal frictioncharges through conducting materialA special type of conductor used to control current.

Superconductor• Certain metals and compounds that

have _____ resistance when their temp. falls below a certain temp called ______ __________.

zerocritical

temperature

Semiconductor• Semiconductors in _________ are

________.• However, as atoms/impurities are

added, or become compounds, these materials begin to be able to ___________________.

pure state insulators

conduct electric charge

Schematic• Diagram or drawing used to build a

_______.• There are two types of circuits.– ________: one path for electrons, if one

bulb goes out they all do– _________: more than one path for

electrons, if one bulb goes out the rest can still shine

circuit

Series

Parallel

Schematic Symbols-Draw symbols on the right side margin of notes

Series Circuit

Parallel Circuit

Open vs Closed Circuit• ______circuit allows electron to flow,

lights on• ______ circuit does not, lights off

ClosedOpen

Circuit Breakers and Fuses• Too many appliances on at the

same time in a home cause the overall resistance of the circuit to be lowered.– Result is a circuit carrying more

electrical current than is safe it is ___________ . Fires can result when this happens.

– _______________ act as a switch and open the circuit.

overloaded

Circuit breakers

Formulas• SI unit for electric charge

– _________ is the quantity of the electricity transported in one second by the current of one ampere. Symbol:

• Potential difference, voltage (V)– 1Joule/coulomb (1J/C)

• Unit for Current (I) = Ampere (amp-A)• Unit for Resistance (R) = Ohm Ω– Formula : Resistance = Volts/Current– Formula with symbols: Ω = V / I

• Unit for Electric Power (P) = Watts (Watts) --- Formula: Power = Volts x Current --- Formula with symbols: P= V x I

Amps vs volts: https://www.youtube.com/watch?v=9iKD7vuq-rY

Coulomb(C)