Transcript PS 6 - Purdyphysicalscience

PS- 6
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Explain how law of conservation of energy applies to the
transformation of various forms of energy
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Explain factors that determine potential and kinetic energy and the
transformation of one to the other
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Explain work in terms of the relationship among the force applied to
an object, the displacement of the object and the energy
transferred to the object
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Use the work formula
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Explain how objects can acquire a static electric charge through
friction, induction, and conduction
PS- 6
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Explain the relationships among voltage, resistance, and current in
Ohm’s law
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Use formula V=IR
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Represent electric circuits
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Compare the functioning of simple series and parallel electrical
circuits
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Compare AC and DC in terms of production of electricity and
direction of current flow
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Explain relationship of magnetism to movement of electrical
charges
In your notes…
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Write your definition (one or two
sentences) of energy
Write at least five TYPES of energy
Write at least five SOURCES of
energy
Make observations…
Make observations
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Steel ball toy, Cell phone, Boiling water,
Watermelon in the face
What is happening? How is it
happening? Why is happening? Be
specific in your descriptions
Discussion
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With a partner discuss your answers
As a pair, share your definition, one type and
one source of energy
Someone explain what is happening with the
steel ball toy, slinky, cell phone, boiling water
What about bacteria, molecules, and plants?
Nature of Energy
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You will read for comprehension
You will be given a sheet to fill in
answers WITHOUT the reading
Energy Diagrams
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Read the directions
Decide what your devices will be and write them out on
your paper leaving room for the energy diagram
Think about what types of energy (see options) the
device uses and write them out
Cut out the appropriate diagram that goes with the
eneryg and paste it in the correct order
See energy box
CLEAN UP!
EXAMPLE
Day 2
Rollercoaster
In your own words
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Explain how the rollercoaster works
Tell the person sitting next to you what your
explanation is (odd numbers first)
Listen to the person sitting next to you
You will need to explain how they think a
rollercoaster works-without looking at their
paper AND even if it is different than yours
Mechanical Energy
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What is a mechanical system?
Mechanical energy
Mechanical Energy
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The sum of potential energy and kinetic energy
in a mechanical system
Total mechanical energy = GPE + KE
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GPE = mgh (mass, gravity, height)
KE = ½ mv2 (1/2 mass, velocity2)
GIZMO
Transferring Energy
Transfer it!- worksheet
Energy Conservation Lab
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Read directions
Write YOUR OWN hypothesis and
explanation.
Notice what position numbers 1-7 are
referring to
The marble move a distance of one
diameter. What does that mean?
How does you find height?
You will have 35 minutes
Part 4 is to be done at your desk
Kinetic Energy lab
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Answer in your own words what is kinetic energy.
Read the directions
You will need a calculator
Do not throw or bounce the balls
Collect data together- #’s 1-3 AND 7-8 ONLY
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15 minutes max
Do calculations on your own # 4-6 AND 9-11
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Finish for homework
Review
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What did we learn yesterday?
What was the lab about?
What factors affect KE and GPE?
Energy
the
ability to cause a change OR do work
Is measured in joules (J)
Types of Energy
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Mechanical
Electrical
Chemical
Light
Sound
Thermal
Write your own
examples!
Energy Transformations
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Chemical energy in gasoline to
mechanical energy in cars
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Chemical energy to electrical energy in
batteries
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Mechanical energy to electromagnetic
energy in hydroelectric plants
Law of Conservation of Energy
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Energy cannot be created or destroyed
but can be transferred
Mechanical Energy Review
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What does GPE depend on?
What does KE depend on?
Kinetic Energy
Mass (kg)
Kinetic Energy
(joules)
KE = 1 mv2
2
Speed (m/sec)
Potential Energy
Mass (kg)
Gravitational
Potential Energy
(joules)
GPE = mgh
Height (m)
Acceleration
of gravity (m/sec2)
What does it look like
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gizmo
Energy Conversion for KE and
PE
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As a pendulum swings, maximum
PE occurs at the top of the swing
KE increases as the pendulum
swings down
Maximum KE is at the bottom of
the swing
PE increases as the pendulum
slows down and moves up the
other side until it is once again at
maximum PE
Where do you
see pendulums?
Pendulum Motion
What does it look like- gizmo
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Make observations
Answer the questions
Heat Energy
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Caused by the motion of molecules
Causes changes in temperature
(average kinetic energy of molecules)
Chemical Energy
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Is stored when chemical
bonds are formed
Is released when chemical
bonds are broken
Ex. When fossil fuels burn
Electromagnetic Energy
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Caused by moving electrons
(electricity)
Also by the energies in the
electromagnetic spectrum (light, xrays, microwaves, etc.)
Solar Energy
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Major source of energy for earth
Convection currents from solar heat
supplies wind and water currents used
to produce electricity
Questions to Ponder
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What is energy and what is it’s unit?
What causes temperature change?
How do fossil fuels provide energy?
Describe the energy transfer in a
pendulum.
How does the sun help provide other
types of energy?
Pendulum Lab- see gizmo
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Read directions individually
Watch instructions
What is the point?
 How could you make a pendulum in a clock run faster?
How do potential and kinetic energy change as the
pendulum swings?
Write your hypothesis
Write your observations ON YOUR OWN as I demonstrate
As a group start at number 5 in the procedure and collect
data
Answer the questions AND label the diagram on your own
Pendulum lab report
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Title?
Purpose?
Hypothesis?
Materials?
Procedure?
Data Table?
Analysis?
Day 4
Work
Definition: The transfer of energy
that occurs when force makes an
object move
For Work to Occur
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An object must move
The motion of the object must be in the
same direction as the applied force on
the object
Unit for work is the Joule (J)
Work and Energy
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Are related since energy is always
transferred from the object doing the
work to the object on which the work is
done
Work is calculated by multiplying force
in Newtons times distance
Force (N)
Work (joules)
W=Fxd
Distance (m)
Machines
What happens when you multiply forces
in machines?
Power
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The rate at which work is done
Is measured in watts (W)
1 kilowatt is 1000 watts
Is calculated by dividing work by time
P=W
t
P = (F x d)
t
Work (joules)
Power (watts)
P=W
t
Time (sec)
What is the power when 600 J of
work is done in 10 seconds?
Application of Calculating Work
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Draw diagram and answer questions in
your notes
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Energy, Work, Power Problems on
your own
Work Smarter
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Lifting vs Pulling
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Which one is easier?
Which one requires more work?
When you calculate work you need a force
and distance- what you need to focus on
is finding the correct force and distance
Energy transformation station
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Wrap it up!
How much power do you have?
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You will need a meter stick, stopwatch,
scratch paper and calculator
Before we start you need to calculate
your Newton force
Electricity Video
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Answer the questions and turn in
Day 6
Big Picture
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Where have we been? And where are we
going?
Electrical energy
Two types
How does it work?
COMPASS EXPLAINS
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Answer the questions in your notes based
on the video
Electricity
Electric Man
-How
is this type of electricity
different from the kind that
a computer uses?
Electric Charge
A. Protons have positive electric charge;
electrons have negative electric charge.
1.) In most atoms, the charges of the protons and
electrons cancel each other out and the atom has no
net charge.
2.)Atoms become charged by gaining or losing
electrons
3.) Static electricity--is the accumulation of excess
electric charges on an object
B. Electrically charged objects
obey the following rules
1.) Law of conservation of charge-charge may be transferred from
object to object but cannot be created or destroyed
2.) Opposite charges attract and like charges repel
3.) Charges can act on each other even at a distance because any
charge that is placed in an electric field will be pushed or pulled
by the field
4.) Electrons move more easily through conductors, like metals
5.) Electrons do not move easily through insulators such as plastic,
rubber, and glass.
How can you get static
electricity?
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Friction- rubbing
Conduction - touching
Induction- charged object -> neutral object
C. Transferring Electric Charge
1.) Charging by contact
a.) The process of transferring charge by
touching or rubbing
b.)Example: Static electricity from your
feet rubbing the carpet
2. Charging by Induction
a.) The rearrangement of electrons on a
neutral object caused by a nearby
charged object
b.) Example: a negatively charged
balloon near your sleeve causes an
area of your sleeve to become
positively charged
3. Static Discharge
a.) A transfer of charge through the air
between 2 objects because of a buildup
of static electricity
b.)Example: lightning
4.) Grounding- using a conductor to direct an
electric charge into the ground
D. The presence of an electric charge can be
detected by an electroscope
The electroscope
DRAW
ME!
Using an electroscope to test an
unknown charge
Electroscope
You will make observations
and record them in your notes
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What happens?
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What is the function of an electroscope?
The leaves _______ ________ if the
leaves and the object touching it have the
same charge.
The leaves _______ ________ if the
leaves and the object touching have
opposite charges.
What does it look like?
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Add concept development worksheet
to this slide….
Watch It!
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Static electricity experiments
Can it happen?
Do it!
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Tape
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2 pieces of tape
Make a fold on one side
Lay one flat on the table-sticky side down
Lay the other one on top-sticky side down
Pull them up and apart
then bring them close to each other
Balloon and water
Balloon and soda can
Day 7
Review
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Energy
Types
Types of Electricity
Reading and Gizmo
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If you are in the green, black and white lab
groups you will be reading and filling in your
notes first
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If you are the yellow, red and orange lab
groups you will do the gizmo activity first
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After 30 minutes we will switch
Electric Current
A. The flow of charges through a wire or conductor is called
electric current
1.)Current is usually the flow of electrons.
2.)Electric current is measured in Amperes (A)
3.)Charges flow from high voltage to low voltage
a.) A voltage difference is the push that causes
charges to move.
b.) Voltage difference is measured in Volts (V)
4.)For charges to flow, the wire must always be connected
to a closed path or circuit.
B. Sources of Electricity
1.) A dry cell battery produces a voltage
difference between it’s zinc container and it’s
carbon suspension rod, causing current to
flow.
B. Sources of Electricity
2.) A wet cell battery contains 2 connected plates
made of different metals in a conducting solution
3.) Wall sockets have a voltage difference across the 2
holes of an electrical outlet and a generator at a
power plant provides this voltage difference.
C. Resistance
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The tendency of a material to oppose the flow of
electrons, changing electrical energy into thermal
energy and light. ( electrical friction)
1.) All materials have some electrical resistance
2.)Resistance is measured in ohms
3.)Making wires thinner, longer, and hotter increases
their resistance.
D. Ohm’s Law
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The current in a circuit equals the
voltage divided by the resistance
Formula: V=IR
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V=voltage
I= current
R= resistance
Electrical Circuits
A. Circuits rely on generators at power
plants to produce a voltage difference
across the outlet causing the charge to
move when the circuit is complete
1.) Series Circuit
a. The current has only one loop to flow through
b. The parts of a series circuit are wired one after
another, so the amount of current is the same through
every part.
c. Open circuit- if any part of a series circuit is
disconnected, no current flows through the circuit
d. Example: a string of holiday lights
2.) Parallel Circuits
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Contain two or more branches for
current to move through
a. Individual parts can be turned off
without affecting the entire circuit
b. Example: the electric circuit in a
house
B. Household Circuits
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Use parallel circuits connected in a logical
network
1.) Each branch receives the standard voltage
difference from the electric company
2.) Electric energy enters your home at the circuit
breaker or fuse box and branches out to wall
sockets, major appliances, and lights.
Electricity in your house
These devices protect
you from short circuits
and fires.
Electrical Safety
2.) Guards against overheating in electrical wires:
a. Electric fuse - contains a small piece of metal
that melts if the current becomes too high, opening
the circuit and stopping the flow of current
b. Circuit breaker - contains a small piece of
metal that bends when it gets hot, opening the
circuit and stopping the flow of current.
C. Electrical Energy
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Electrical energy is easily converted to
mechanical, thermal, or light energy.
1.) Electrical Power
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The rate at which electrical energy is
converted to another form of energy.
a. Electrical power is expressed in watts (W)
b. Power = current x voltage difference
c. P (watts) = I (amperes) x V (volts)
Match it!
Mythbusters
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Myth: Stay off the phone or computer and
out of the shower during a lightning storm.
There will be questions from this video on
the test
Write notes to help you remember what
happened. (i.e The test dummy’s name
and the results of the experiment)
Day 8
Review
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Static electricity vs Current electricity
Why does a bulb light?
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A tungsten filament has a high
resistance and glows white
when it reaches 2,500 oC.
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Argon gas inside the bulb is
"inert", it doesn't chemically
react with the tungsten so it
protects it from air for use over
and over again.
How does it light?
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Needs a source of voltage difference to
allow electrons to flow
Needs a path for current to get to the bulb
and needs to be closed
Make observations on which simple circuit
works and write the answer at the end of
your lab
How do you represent this path?
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Wire
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Battery
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Bulb
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Resistance
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Switch
What do the symbols look like it a circuit?
Draw it!
Which way does current flow?
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Either positive or
negative charges can
flow.
It depends on the
materials making up
the circuit. We label
circuits from high to
low current.
What’s a Circuit
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Read directions carefully
This is timed
You will work in a group for 15 minutes
Answer questions for 15-20 minutes
Answer EVERY question
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Draw symbols and a circuit diagram
The questions you don’t finish in the
designated time you will finish at home
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In SERIES circuits, current
can only take one path.
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In PARALLEL circuits the
current can take more than
one path.
Types of Circuits
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Read directions carefully
You will work in as a group to fill out
ONE lab sheet. Everyone should
contribute.
Answer EVERY question
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Draw symbols and a circuit diagram
Day 8
Go over Circuit labs
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Current
Circuit
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Parts: wire (conductor), battery, bulb, switch
Open/closed
Series/parallel (AND/OR)
Open or Closed
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See worksheet
Trace with your pencil the path
Burglar and Car alarm
Current, Voltage and Resistance
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Review- read your notes silently
How do you measure current, voltage,
resistance?
How do these things change when one of
them is changed?
Voltage, Current and Resistance lab
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Read your instructions as I explain
Multimeter is how you will measure
voltage, current and resistance
The red lead goes on in the middle hole
and the black lead goes in the bottom hole
on the meter
What does a battery do?
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A battery uses chemical energy to move charges.
If you connect a circuit with a battery the charges
flow out of the battery carrying energy.
Measuring voltage of a dry cell
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Set the meter to 20 DC
volts.
Touch the red (+) lead of
the meter to the (+)
battery terminal.
Touch the black (-) lead
of the meter to the (-)
battery terminal.
Adjust the meter dial as
necessary.
Measuring voltage in a circuit
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Build a circuit as
instructed in your lab
sheet
Measure the voltage
across the battery
exactly as before.
DO NOT
DISCONNECT THE
CIRCUIT.
NOTE: Since voltage is measured from
one point to another, we usually assign
the negative terminal of a battery to be
zero volts (0 V).
Measuring Current
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Set the meter to 200m A.
Touch the red (+) lead to
the (+) battery terminal.
Touch the black (-) lead to
the (-) light bulb.
Current can't be measured
unless the charges flow
through the meter.
Measuring Current in a circuit
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This is the current
at point A
Record it
Do the same thing
for B except the red
lead is going to be
on the light bulb
and the black is
going to be on the
battery
Answer the questions on your
own
Measuring Resistance
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Set the meter to
measure resistance
200 (W).
Set the black and red
leads on opposite ends
of the objects.
Day 9
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Reference sheet
calculator
Review lab
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What did you do?
What did you learn about voltage, current
and resistance?
Ohm’s Law
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Describes the relationship among
current, voltage and resistance
Watch it!
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What happens to the batteries when V
gets bigger?
What happens to the blue arrows when V
gets bigger?
Draw 4 scenarios
Description example: As voltage
increases, current increases and
resistance decreases
Ohm’s Law Problems
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In a simple house circuit there is a current of
0.6 amps flowing through a lamp with a
resistance of 20 ohms. What is the voltage in
the circuit?
V
I
R
Ohm’s Law Problems
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Find the resistance in a circuit that has a
voltage of 120 volts and a current of 4 amps.
V
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Ohm’s law lab
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2 circuits
You are going to see how voltage, current
and resistance are related and how to
graph them
Potentiometer vs fixed resistance
Don’t leave the light bulbs lit!!!
Ohm’s law lab
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Potentiometers are a type of "variable" resistor that
can change from low to high. It has a positive and
negative end.
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They are wired so that as you turn the knob, it
changes the distance the current has to flow.
Graphing and Ohm's law
Day 10
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Do notes for homework
Go over Ohm’s law lab
Circuit Diagrams
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Draw a circuit diagram of 3 light bulbs in
series with a switch and 2 batteries.
Circuit Diagrams
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Draw a circuit diagram of 2 light bulbs and
batteries in parallel with a switch
Circuit Diagrams
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Draw a circuit diagram of a light bulb and
resistor wired in series with a generator
and a switch.
Circuit Diagrams
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Answer the following questions about
your diagrams.
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If a light bulb was unscrewed in diagram 1,
what would happen and why?
Why would the circuit in diagram 2 be better
for the batteries than wiring them in series?
What would happen to current and
resistance if another path was added to
diagram 2?
Circuit Diagrams
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Answer the following questions about
your diagrams.
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If a light bulb was removed from diagram 2
what would happen and why?
If another light bulb was added to diagram 3,
what would happen to the resistance, current
in the circuit and brightness of the bulb?
Energy & Electricity Review
Energy
Review
1.) Energy cannot be created or destroyed
2.)
Energy conversion to turn on a light switch
3.)
4.) W = F x d force applied over distance
5.) Work , force, and displacement have
magnitude and direction .
6.) a.) a force must be applied to the
object
b.) The object must move in direction
of the applied force
8.) When a net force causes work to be done on an object
and it moves, work is transformed to kinetic energy.
9.) If an object is lifted to some height it gains Gravitational
Potential Energy .
10.) The unit for work is the Joules (J) .
11.) W = f x d = 15N x 5m = 75 J
12.) f = W/d = 50 J / 2m = 25 N
13.) d = W / f = 75 J / 25 N = 3m
Electricity
Review
1.) Protons – (+) nucleus
Neutrons – () nucleus
Electron – (-) electron cloud
2.) like charges – repel
unlike charges – attract
3.) objects become negatively charged by gaining
electrons
objects become positively charged by losing
electrons
4.) a.friction: rub one object against
another ---electrons leave one object
and stick to another
b.conduction: electrons transferred by
touching –2 objects then have the
same charge and will repel each other
c.induction: charged by bringing a
charged object near neutral object /
charges separate
6.) mechanical energy to electrical energy
7.) provides energy that pushes & pulls
electrons through the circuit (V) / electrical
potential energy
8.) one terminals is negative (extra electrons)
other terminal has deficit of electrons (+) /
pushed by negative terminal and pulled by +
9.)flow of electrons through a conductor
Amps (A)
10.) when electrons flow through a wire continually
running into things and bouncing around – ohms
(W)
11.) will slow flow of current because it is harder for
the current to get through the conductor –heat
12.) large diameter – less resistance
long wires – greater resistance
increase in temperature – increases resistance
13.) Electric devices provide much of the resistance in
a circuit .
14.)a. 1 volt will pull 1 amp through 1 ohm of
resistance
b. If voltage increases and resistance stays the
same, current increases.
c. If voltage stays the same and resistance
increases, then current decreases.
15.) Sources of voltage for a circuit include chemical
cells and generators.
16.) Resistors, light bulbs, and other electronic
devices are a source.
17.) V= I x R
=  A x  W = 5 V
18.) R= V/ I
= 6 V /  A = 3 W
19.) I = V/ R
=  V /  W
=6A
20.) a single path circuit for electrons to flow
through
21.) total resistance increases & current
decreases
22.) dim because current decreases
23.) all go out because circuit opened
24.) more than one path for electrons to flow
25.) voltage – stays the same
current - increases with each path
resistance – reduces with each path
26.) the others keep burning and they get brighter
27.) series – increases voltage (decreases life of battery)
parallel - stays the same (increases life of battery)
28.)
28.) cont.
Day 11
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You need a textbook
WHAT?!?!?!?!?!?
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Magnet boy
Read p. 165-169
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Take your own notes-FILL IN STUDENT
NOTES
Draw figure on p 169 – magnetic field
lines
Answer questions #3 and #4 on p 180
Pair share your summary
Magnetism
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Refers to the properties and interactions of
magnets
Permanent Magnets
- material that keeps its magnetic properties
even when it is NOT close to other
magnets
- Composed of a substance called magnetite
Examples of Permanent Magnets
Properties of Magnets
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Magnets have two opposite
poles.
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north
south
Magnets exert forces on
each other and it
strengthens as magnets
get closer to each other
The forces depend on the
alignment of the magnetic
poles.
Poles
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Magnetic vs Geographic
Magnetic Field Lines
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The space around a magnet in which
another magnet experiences a magnetic
force
The lines start at the north pole and end at
the south pole (it has direction)
Depends on:
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the magnetic material
how much it is magnetized
Magnetic Poles again
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Where are the field lines the closest
together?
poles
It is the place where the force is strongest
How does a compass work?
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The compass needle is a small bar magnet
with a north pole and a south pole
The magnetic force causes the needle to spin
and line up in the magnetic field of the earth
Other Magnetic materials
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Not all metal objects will be attracted to
the magnet
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Only iron (ferromagnetic), cobalt and nickel
How?
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All atoms have electrons and some electrons
possess magnetic properties
The field that is created caused large groups
of these atoms to align their magnetic poles,
which causes the material to behave like a
magnet
Magnetic Domains
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groups of atoms with aligned poles
Example: Iron (ferromagnetic substance)
Unmagnetized
Magnetized
Magnetism Observations
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Watch instructions!
Put iron filings on your lab paper –NOT ON
THE MAGNET
Make observations and record them on your
lab sheet
Magnetism Video
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Take notes
Day 12
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Need textbook
EMI demo
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What object is moving in and out of the
wire coil?
What is happening to the ammeter?
What does this mean?
Does electricity produce magnetism?
How do you make one?
Electricity and Magnetism
Relationship

In 1820 Hans Christian Oersted found that
electricity produces a magnetic field and the
direction of field (N-S) changes with the
direction of the flow of electricity
Electromagnets
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The magnetic field surrounding current
carrying wire can be made stronger with
this device
An electromagnet is a temporary magnet
made by wrapping a wire coil carrying a
current around an iron core

There are 3 ways that the strength of the
electromagnet can be increased:
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Add more turns of the wire
Add a core (like iron)
Increase the current
Real life example- read p 171
Applications of electromagnets
mag-lev train
Applications of electromagnets
doorbell
Applications of electromagnets
toaster
Applications of electromagnets
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speakers
Electromagnets Rotate
Motors

Electric motors change
electrical energy to
mechanical energy
Simple Motor
How does it work?

Motors contain an armature that becomes
magnetized when current runs through

Armature spins because of the other
magnets alternately arranged
Use a single magnet go attract and repel
magnets in a rotor by flipping its poles.
Electromagnetic Induction

What do you think this term means?
Used in alternating current in generators

Definition:


Whenever a wire or a coil of wires moves
relative to a magnetic field an electric current
is produced
EMI –Quick Review sheet
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
The movement of electric charges can
create magnetic fields.
An electromagnet is a solenoid (coil of wire)
with a ferromagnetic core
Electromagnetic devices change electrical
energy into mechanical energy
Electromagnetic induction is the process of
generating a current by moving an electrical
conductor
Generators



Changes mechanical energy into electrical
energy by rotating a coil of wire in a
magnetic field
Generators use electromagnetic induction
Generators produce AC current
Generating Electricity


A power plant generator contains a turbine that turns
magnets inside loops of wire to generate electricity.
A flashlight uses a magnet to store electricity to turn it on
ELECTRIC CURRENT
-The
flow of electrons through a wire.
-There are two types: direct and alternating
Direct Current (DC)


Is produced using a chemical cell
(battery) or a solar cell
Flows in ONE direction
Direct Current (Cont)


Electrons are negatively charged and are
attracted to the positive terminal of the
battery
When a circuit is connected, electrons flow
from positive to negative terminal
Alternating Current (AC)



The current moves back and forth within
the circuit
This current comes out of the outlets in
homes and other buildings
Is produced by a generator using
electromagnetic induction (see separate
handout)
How AC Current is Produced

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The magnet in a generator spins causing the
terminals in the generator to alternate
between positive and negative
Electrons are repelled by the negative terminal
and attracted to the positive terminal
Because the terminals are continually
changing from positive to negative the current
constantly changes directions
Electricity and Magnetism: Are they
related?
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
At each station there is a demonstration
of electricity and magnetism
Follow instructions and record YOUR
OWN GOOD observations
You will have 3-4 minutes at each station
If you blow the bulb on the generator you
will get a zero
Tie It together
References
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http://www.pajamacity.com/images/costume-famiy-guy-electricman.jpg
http://www.lisefizik.com/lise3/resim2/electroscope2.gif
http://www.everydayguide.com/how-does-a-battery-work/
http://academic.pgcc.edu/ent/ENT%20171%20Online%20Project/ind
ex.htm
http://ecx.images-amazon.com/images/I/31Q330BV03L._SS400_.jpg
http://www.deskpicture.com/dps/sports/skier_1.html
http://www.solarnavigator.net/compass.htm
http://www.explainthatstuff.com/magnetism.html
http://www.cpsc.gov/cpscpub/prerel/prhtml05/05592.html
http://www.uh.edu/engines/epi1468.htm