Chapter 6 – Electricity. 6.1 Electric Charge Positive and Negative Charges Matter is composed of...
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Transcript of Chapter 6 – Electricity. 6.1 Electric Charge Positive and Negative Charges Matter is composed of...
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
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
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
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
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
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
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
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
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)