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Physical Science Chapter 17
Electricity Physical Science Chapter 17 Physical Science chapter 17
Physical Science chapter 17
Electric charge Neutral Equal positive and negative charges
Positive Fewer negative charges (lost electrons) Negative More
negative charges (gained electrons) Physical Science chapter 17
Physical Science chapter 17
Static electricity The accumulation of electric charges on an
object. Physical Science chapter 17 Physical Science chapter
17
Charges Like charges repel Opposite charges attract Physical
Science chapter 17 Physical Science chapter 17
Charging by contact A charged object touching an uncharged object
causes electrons move around until they are evenly spread
throughout both objects. When the charged object is removed, the
other object has a charge See page 589 Physical Science chapter 17
Physical Science chapter 17
Charging by induction A charged object causes the electrons on a
neutral object to rearrange themselves. The charged object and the
neutral object are then attracted to each other. See page 588
Physical Science chapter 17 Physical Science chapter 17
Conductor Material that allows electrons to move easily through it
metals Physical Science chapter 17 Physical Science chapter
17
Insulator A material that doesnt allow electrons to move through it
easily Plastic Wood Rubber Glass Physical Science chapter 17
Physical Science chapter 17
Discuss What is static electricity? What is the difference between
a conductor and an insulator? Physical Science chapter 17 Physical
Science chapter 17
Electric force Push (repulsion) or pull (attraction) experienced by
charged particles. Depends on charge and distance Larger charges
make larger forces Smaller distances make larger forces Physical
Science chapter 17 Physical Science chapter 17
Electric field How a charged particle exerts a force on other
particles. The field is strongest closest to the particle. Field
lines point in the direction of the force ona positive charge.
Field lines never cross Physical Science chapter 17 Physical
Science chapter 17
discuss What is an electric field? Physical Science chapter 17
Electrical Potential Energy
Energy an electric charge has based on its position in an electric
field Physical Science chapter 17 Physical Science chapter 17
Moving electrons Electrons move from areas of high potential energy
to areas of low potential energy When the potential energies are
equal, the electrons stop Physical Science chapter 17 Physical
Science chapter 17
Potential Difference Potential energy change divided by charge
Measured in volts (V) Often called voltage Physical Science chapter
17 Physical Science chapter 17
Electric Current The flow of electrons through a conductor Amount
of current depends on number of electrons passing a point in a
given time. Measured in amperes or amps (A) 1 ampere is 1 coulomb
of charge per second 1 coulomb is the charge of 6.24 x 1018
electrons Physical Science chapter 17 Physical Science chapter
17
Batteries Made of electrochemical cells Have a potential difference
between the positive and negative terminals Electrons are released
in a chemical reaction As long as the reaction occurs, the battery
works. Dry cell batteries contain a pastelike electrolyte Wet cell
batteries contain a liquid electrolyte Physical Science chapter 17
Physical Science chapter 17
Resistance The tendency of a material to resist electron flow
Measured in ohms (W) Conductors have low resistance. Insulators
have high resistance. Physical Science chapter 17 Physical Science
chapter 17
Ohms Law The current in a circuit depends on both voltage and
resistance Physical Science chapter 17 Physical Science chapter
17
Example Find the current flowing through a wire if its resistance
is 20 W and it is connected to a 12-V battery. Physical Science
chapter 17 Physical Science chapter 17
You try Find the current flowing through a wire if its resistance
is 20 W and it is connected to a 6-V battery. Physical Science
chapter 17 Physical Science chapter 17
Semiconductors Conduct electricity under certain conditions In pure
state insulators With carefully added impurities conductors Used in
electronics Physical Science chapter 17 Physical Science chapter
17
Discuss What is current? What is resistance? What three quantities
are related by Ohms law? Physical Science chapter 17 Physical
Science chapter 17
Circuit A closed path for electrons Electrons continue to flow as
long as there is a potential difference Common source is a battery
Physical Science chapter 17 Physical Science chapter 17
Schematic diagrams Used to show the construction of a circuit
Symbols used shown on page 602 Physical Science chapter 17 Physical
Science chapter 17
Series circuits The current only has one possible path. The current
is the same everywhere. If one part goes out, the circuit is broken
and it wont work. Physical Science chapter 17 Physical Science
chapter 17
Parallel Circuits Contain separate branches for current to move
through. The current is different in each branch. More current goes
through branches with less resistance. The potential difference is
the same in each branch. When one branch is opened, the current
continues to flow through the other branches Physical Science
chapter 17 Physical Science chapter 17
Discuss Section 3 Review #1 on page 607 Physical Science chapter 17
Physical Science chapter 17
Power The rate at which work is done chapter 13 Electrical power
the rate at which electrical energy is converted to another form of
energy Physical Science chapter 17 Physical Science chapter
17
Power Expressed in watts (W) or kilowatts (kW) Found by multiplying
current times voltage. Physical Science chapter 17 Physical Science
chapter 17
Example A lamp operates with a current of A and a potential
difference of 120 V.How much power does it use? Physical Science
chapter 17 Physical Science chapter 17
You try A microwave oven uses 1000 W of power.The voltage source is
120 V.What is the current flowing through the microwave? Physical
Science chapter 17 Physical Science chapter 17
You try The current in the heating element of an iron is 5.0 A.If
the iron dissipates 590 W of power, what is the voltage across the
iron? Physical Science chapter 17 Physical Science chapter 17
You try A single solar panel for home use puts out550 W of
electrical power.If the electrical current produced by this panel
is 4.2 A, calculate the voltage generated by the panel. Physical
Science chapter 17 Physical Science chapter 17
Household circuits Mostly parallel circuits. Overheating protection
is needed. Fuses Contain small pieces of metal that melt when the
current gets too high Must be replaced when blown Circuit breakers
Contain metal that bends when the current gets too high Can be
reset by flipping a switch Physical Science chapter 17