Download Magnetism - South High School

Magnetism
9/10
Turn in circuit lab from yesterday.
1. Create a diagram of a two way switch.
2. Take the electromagnetic instruction sheet,
circle the words you don’t understand.
Underline main idea of each step.
• Magnetic field – area where magnetic force
acts.
9/11
1. What comes to mind when you see this picture?
2. What do you think causes this?
Scan the text
• Do auroras occur only on Earth?
• Because auroras are caused by the interactions of solar winds and solar
flares with the magnetic fields of a planet, you'd think they'd happen on
other planets as well. What you need is:
• Solar flares and winds that provide the charged particles and energy to
interact with a planet’s magnetic field
• A planetary magnetic field (probably of some strength) that traps
electrons from space
• A planetary atmosphere that contains ionic gases that interact with
energetic electrons from the magnetic field and produce light through
excitation and relaxation of their electrons
So, with these conditions, we have observed auroras on Jupiter
and Saturn. Both planets have powerful magnetic fields and
atmospheres with ionized gases, mainly hydrogen and helium.
The Hubble Space Telescope caught images of auroras on
Jupiter, and the Cassini probe orbiting Saturn has
photographed auroras there.
What is Magnetism?
• Magnetism is the attraction of a
magnet to another object.
36.2 Magnetic Fields
Iron filings sprinkled on a sheet of paper over a bar
magnet will tend to trace out a pattern of lines that
surround the magnet.
magnetic field -The space around a magnet, in which
a magnetic force is exerted
The shape of the field is revealed by magnetic field
lines.
What are Magnetic Poles?
• Magnets have two ends, called
magnetic poles.
• Magnetism is strongest at the poles
of a magnet.
What are the magnetic
properties of the Earth?
• The Earth has an immense magnetic
field around it called the
magnetosphere.
36.6 Magnetic Forces on Moving Charged Particles
The deflection of charged
particles by magnetic fields
provides a TV picture.
Charged particles from outer
space are deflected by Earth’s
magnetic field, which reduces
the intensity of cosmic
radiation.
A much greater reduction in
intensity results from the
absorption of cosmic rays in
the atmosphere.
Magnetic Poles
• Magnetic poles that are alike repel each
other.
• North repels North
• South repels South
• Poles that are not alike attract each other
• North attracts South
• South attracts North
What is a Magnetic Field?
• The magnetic force exerted in the
region around the magnet is the
magnetic field.
• This allows magnets to interact
without touching.
What are Magnetic Field Lines?
• Magnetic Field Lines spread out from
one pole, curve around the magnet,
and return to the other pole.
What do atoms have
to do with it?
• All atoms have magnetic fields
because of the charged particles
inside.
• Most atoms’ magnetic fields point in
random directions, so they all cancel
each other out.
36.3 The Nature of a Magnetic Field
Spin Magnetism
Every spinning electron is a tiny magnet.
• A pair of electrons spinning in the same
direction makes up a stronger magnet.
• Electrons spinning in opposite directions
work against one another.
• Their magnetic fields cancel.
Magnetic Fields
Magnetic fields
• produced by two kinds of electron motion
– electron spin
• main contributor to magnetism
• pair of electrons spinning in same direction creates a stronger
magnet
• pair of electrons spinning in opposite
direction cancels magnetic field of the
other
– electron revolution
36.3 The Nature of a Magnetic Field
Most substances are not magnets because the
various fields cancel one another due to
electrons spinning in opposite directions.
In materials such as iron, nickel, and cobalt,
however, the fields do not cancel one another
entirely.
An iron atom has four electrons whose spin
magnetism is not canceled.
Each iron atom, then, is a tiny magnet. The
same is true to a lesser degree for the atoms of
nickel and cobalt.
What do atoms have
to do with it?
• In magnetized material, all or most
of the magnetic fields are arranged
in the same direction.
• A material that keeps its magnetism
is called a permanent magnet.
36.4 Magnetic Domains
The magnetic fields of individual iron atoms are
strong.
• Interactions among adjacent iron atoms
cause large clusters of them to line up with
one another.
• magnetic domains
clusters of aligned atoms
• Each domain is perfectly magnetized, and is
made up of billions of aligned atoms.
• The domains are microscopic, and there are
many of them in a crystal of iron.
36.4 Magnetic Domains
The arrows
represent domains,
where the head is a
north pole and the
tail a south pole.
Poles of neighboring
domains neutralize
one another’s
effects, except at
the ends.
36.9 Earth’s Magnetic Field
The compass aligns with the
magnetic field of Earth, but the
magnetic poles of Earth do not
coincide with the geographic
poles.
The magnetic pole in the Northern
Hemisphere, for example, is
located some 800 kilometers from
the geographic North Pole.
This means that compasses do
not generally point to true north.
The discrepancy is known as the
magnetic declination.
36.9 Earth’s Magnetic Field
Currents in the molten part of Earth
beneath the crust provide a better
explanation for Earth’s magnetic field.
Most geologists think that moving
charges looping around within Earth
create its magnetic field. Because of
Earth’s great size, the speed of charges
would have to be less than one
millimeter per second to account for the
field.
Another possible cause for Earth’s
magnetic field is convection currents
from the rising heat of Earth’s core.
Perhaps such convection currents
combined with the rotational effects of
Earth produce Earth’s magnetic field.
36.9 Earth’s Magnetic Field
More than 20 reversals have taken place in the past 5
million years. The most recent occurred 780,000
years ago.
We cannot predict when the next reversal will occur
because the reversal sequence is not regular.
Recent measurements show a decrease of over 5% of
Earth’s magnetic field strength in the last 100 years.
If this change is maintained, there may be another
field reversal within 2000 years.
1. What happens if you break a
magnet in half?
S
2. Draw a picture of what it will
look like if you spread iron
fillings on a bar magnet.
N
36.1 Magnetic Poles
If you break a bar magnet in
half, each half still behaves
as a complete magnet.
Break the pieces in half
again, and you have four
complete magnets.
Even when your piece is one
atom thick, there are two
poles. This suggests that
atoms themselves are
magnets.
MRI
• Magnetic resonance imaging (MRI) is a test
that uses a magnetic field and pulses of radio
wave energy to make pictures of organs and
structures inside the body
• Sucks metal out
Magnets make you feel better?
•
•
Q: What is Transcranial Magnetic Stimulation (TMS), and how does it help depression?
A: TMS activates certain parts of the brain by using electrical energy passed through a coil of
wires to create a powerful magnetic field. During the procedure, energy from this magnetic field
is transferred into a patient's brain by means of the coil device applied to the head. Unlike direct
electrical energy, energy from the magnetic field passes through skin and skull, activating the
brain painlessly and without surgery or sedation. We apply TMS to the front area of the brain, an
area associated with mood regulation. Not unlike many anti-depressant medications, TMS affects
brain functions and chemical activity, effectively "jump -starting" mood regulation structures in
the brain, resulting in dramatic improvements in depressed patients.
Accelerators
LHC
A superconductive
disk on the bottom,
cooled by liquid
nitrogen, causes the
magnet above to
levitate. The floating
magnet induces a
current, and
therefore a magnetic
field, in the
superconductor, and
the two magnetic
fields repel to
levitate the magnet.
LHC Experiments
The World Wide Web
Importance of Science
For more information on the CERN HST Programme
http://teachers.web.cern.ch/teachers/
9/12
• What is the largest magnet in the world?
• How do these birds know where to go?
•
•
•
“Is it true that the Earth‘s magnetic field is about to flip?
Like football teams at half time, geophysicists think that the Earth’s magnetic poles could
soon switch ends with the magnetic north pole becoming south, and the magnetic south pole
becoming north. Fortunately, when they say ‘soon’ geophysicists are thinking in geological
timescales and they actually mean sometime in the next few thousand years.
It’s thought that the Earth’s magnetic field is generated by the molten iron core at the centre
of the planet. The molten iron has currents of its own, just like an ocean, and these moving
currents create the magnetic field. But the currents are not consistent and the Earth’s
magnetic field moves around, with the magnetic north pole currently drifting by about 10
miles a year.”
• http://www.physics.org/facts/frog-magneticfield.asp
Fun fact
• Dogs use the Earth’s magnetic field when
they’re relieving themselves. Not only that,
but canines choose to do so in a north-south
axis, Says a new study published in the
Frontiers in Zoology
Great questions from yesterday
• How do they make magnets?
- stay tuned, Monday we will find out
• What would happen if we had no
magnetosphere?
-Solar flares might knock out power grids and where plenty of sunblock and
the northern lights would no longer be northern, they would be every where
• Doesn’t science cause war?
• Science creates technology, it is what humans decide to do with it is what
creates war
Homework due monday
Background: “What is a magnetic field? What is a magnet?”
reading
Claim : How were you able to create a compass
•
Evidence : How were you able to tell it was a compass? (include
drawings)
•
Reasoning : Explain how your compass worked. Your explanation
should include magnetic domains, magnetosphere, south pole
north pole, magnetic field. What future questions do you have?
9/15
• How does the compass show the magnetic
field?
• What do electrons have to do with magnetism
• How was electricity discovered?
• Turn in reports
• Ancient battery near Bagdad
An Aurora Borealis Fun Fact
• Seeing the Northern Lights is not a good thing to
some people. It is a traditional belief that when the
northern lights are shinning in the night sky, it
means that the spirits are dancing because the
know that somebody is going to begin their journey
to the spirit world/heaven.
Future questions
What do Electric Currents
have to do with Magnets?
• An electric current produces a
magnetic field.
• The direction of the current
determines the direction of the
magnetic field.
Characteristics of Electromagnets
• Strength depends on the number of coils
and the size of the iron core.
• The greater the number of turns the coil
has the stronger the magnet will be.
• The closer the coils are the stronger the
magnet will be.
36.5 Electric Currents and Magnetic Fields
Iron filings sprinkled on paper reveal the
magnetic field configurations about
a.a current-carrying wire
b.a current-carrying loop
c.a coil of loops
36.5 Electric Currents and Magnetic Fields
A superconducting electromagnet can generate a
powerful magnetic field indefinitely without using
any power.
Superconducting magnets can also be found in
magnetic resonance imaging (MRI) devices in
hospitals.
• At Fermilab near
Chicago,
superconducting
electromagnets
guide high-energy
particles around the
four-milecircumference
accelerator.
• http://www.pbs.org/
wgbh/nova/physics/
cern.html
What is an Electromagnet
• An Electromagnet -a strong magnet
that can be turned on and off.
• It consists of a current-carrying wire
wrapped around an iron core.
• Hans Christian Oersted found that a compass
he was using reacted when a battery in his lab
was switched on and off
How a speaker works
• All you need is an
electromagnet, permanent
magnet and a vibrating cone
• http://www.physics.org/article
-questions.asp?id=54
• What else could you use
electromagents for?
335 × 311 education.com
9/16
• What are some modifications that can be
done to increase the strength of the
electromagnet?
Electric Currents and Magnetic Fields
Connection between electricity and magnetism
Magnetic field forms a pattern of concentric circles around a
current-carrying wire
• when current reverses direction,
the direction of the field lines
reverse
Magnetic Forces Current-Carry Wires
Magnetic Force and Levitation
• When an upward magnetic
force is greater than gravity,
then an object can levitate.
• A magnetically levitated
vehicle is shown in the
figure to the right – a
magplane.
• No friction, no vibrations
• http://www.ru.nl/hfml/research/levitatio
n/diamagnetic/
• http://www.youtube.com/watch?v=tipublpl16
4 - understanding electricity – the science
channel
36.8 Meters to Motors
In a simple DC motor, a permanent magnet produces a magnetic
field in a region where a rectangular loop of wire is mounted.
• The loop can turn about an axis.
• When a current passes through the loop, it flows in
opposite directions in the upper and lower sides of the loop.
• The loop is forced to move as if it were a galvanometer.
Motors and Generators
• Electric Motor – a device that
changes electric current into
mechanical energy.
• Generator – a device that changes
mechanical energy into electrical
current.
Motor and Generator
CHECK YOUR ANSWER
A motor and a generator are
A.
B.
C.
D.
similar devices.
very different devices with different applications.
forms of transformers.
energy sources.
Motor and Generator
CHECK YOUR ANSWER
A motor and a generator are
A.
B.
C.
D.
similar devices.
very different devices with different applications.
forms of transformers.
energy sources.
Electromagnetic Induction
Electromagnetic induction – Moving a permanent
magnet and a wire will induce a current
• discovered by Faraday and Henry
• voltage is induced with change of magnetic field strength in a
coil of wire
Electromagnetic Induction
Electromagnetic induction (continued)
• induced voltage can be increased by
– increasing the number of loops of wire in a coil
– increasing the speed of the magnet entering and leaving
the coil
• slow motion produces hardly any voltage
• rapid motion produces greater voltage
Power Production
Using Faraday and Henry’s discovery of electromagnetic
induction, Nikola Tesla and George Westinghouse
showed that electricity could be generated in sufficient
quantities to light cities.
How is electricity generated?
• Demo: Magnet, wire, bulb
http://www.bbc.co.uk/bitesize/standard/physics/energy_matters/generation_of_ele
How is electricity generated?
• Demo: Hand-crank
electrical generator
• Demo: Faraday
flashlight
http://www.secondchancegarage.com/public
/91.cfm
9/17
• How many motors are in a car, list them.
• What are the three requirements for electric
current to be produced?
• What is the difference between a motor and a
generator?
9/18
• What is the picture about?
• What are the 3 ways to increase the induced
current?
• Is the system using AC or DC current, Why?
• Tomorrow : Quiz and notebook check
• Electromagnetic wave – A wave of energy consisting of
electric and magnetic fields
• Electromagnetic waves come from accelerating electric
charges, often electrons in atoms. The energy given off
travels in a wave that is partly electric and partly magnetic
Voltage generated = speed * number of turns * strength of field
area / time
where, as indicated in the figure:
Σ is a surface bounded by the closed contour ∂Σ,
E is the electric field, B is the magnetic field.
dℓ is an infinitesimal vector element of the contour ∂Σ,
dA is an infinitesimal vector element f surface Σ. If its direction is orthogonal to that
surface patch, the magnitude is the area of an infinitesimal patch of surface.
• Does a compass line up perpendicular or
parallel to magnetic field lines?
• Does a compass line up perpendicular or
parallel to magnetic field lines?
• The compass points parallel to the magnetic
field.
• Does a compass line up perpendicular or
parallel to magnetic field lines?
• The compass points parallel to the magnetic
field.
• Why are the Aurora’s only located near the
poles?
Moving electrons will interact with
• A. an electric field
• B. a magnetic field
• C. Both a and B
• D. none of the above
Moving electrons will interact with
• A. an electric field
• B. a magnetic field
• C. Both a and B
• D. none of the above
• On a half sheet of paper describe how
electricity is generated?
• Underline the content vocabulary:
• Why is this important to know?
9/19
• What do you think is the source of most
commercial generators?
• If an object sticks to a magnet, is the object a
temporary magnet or a permanent magnet?
• Are you ready for the quiz
• Notebook check - # of dates from 9/8
Hints
• # What moves most generators?
• #12 cosmic rays are solar flares (think of
Northern lights)
9/22
• What is the most common type of generator
used in the United states? The World?
• What comes to your mind when you hear the
word energy?
• How do we get energy?
Energy sources
http://commons.
wikimedia.org/wiki/F
ile:2011_US_electric
ity_generation_by_s
ource.png
How is electricity generated?
• Demo: Magnet, wire, bulb
http://www.bbc.co.uk/bitesize/standard/physics/energy_matters/generation_of_ele
How is electricity generated?
• A steady supply of heat to turn water to steam
can be provided by:
– Burning stuff (coal, natural gas, wood, etc.)
– Controlled nuclear reactions
– The sun
– The Earth’s heat
• Or, turbines can be directly turned using:
– Flowing water
– Wind
• What resources should we use to obtain the
energy to power our homes, schools and
businesses?
• Wind, coal, oil, natural gas, nuclear power,
solar, geothermal, something else?
• Turbine – part of a generator that has a part
with blades that are caused to spin by
pressure from water, steam, or air
Small group discussion
• Go to
http://www.iea.org/statistics/statisticssearch/
and find at least one country that generates
its electricity with a very different balance of
sources than the U.S.
• .
Energy Sources
http://www.iea.org/statis
tics/statisticssearch/
Why does Norway lead the world in hydroelectricity?
The environment dictates the
energy source.
9/24
• What is the main idea behind your
presentation?
• What future questions are you going to
research today?
• - find two sources
• Optional – print 1 or 2 pictures
9/25
• On a scale of 1-5 how confident do you feel
about explaining the content of your poster.
• What are some key vocabulary words in your
poster?
• What more do you need to do?
• How can I help?
• Samples of peer assessment
9/26
• What is the most interesting thing you have
learned from your research?
• What are characteristics of a good
presentation?
• 10 minutes – polish presentation
• 30 minutes – gallery walk
• 10 minutes – reflection
• Grade yourself out of 10 points (see rubric)
• What percentage of the work did each group
member do?
• On a separate sheet of paper create a reflection on your poster.
• What did you think you did well?
• What do you think might make your poster stronger? Did you enjoy the
gallery walk? How would you compare this way of learning to other ways
of learning?
• Discuss what you thought of your classmate’s presentations. Write down
three of the most interesting things you learned?
• Give a brief summary of your poster
PSTL 1163: Physics by Inquiry
Environmental connections
Unit 1: Environmental impacts of electricity
generation
Day 3: Environmental impacts
Key questions
• What are the environmental impacts of
different sources of energy for generating
electricity?
• What are the other impacts of the generation
and distribution of electricity?
Fossil fuels
• Drilling/mining for fossil fuels disturbs the
environment
• Resulting pollutants (besides CO2)
– Gases: CO, SO2, NOx: Cause acid rain, ground level ozone,
fine particulates --> respiratory problems
– Solids: Coal ash, containing mercury, lead, cadmium,
arsenic, etc.: Cause neurological damage and heart
disease
• 130 million tons annually, enough to fill the Grand Canyon
• Coal ash disposal is regulated by the states, rather than the
federal government (What are the implications?)
• People living closest to power plants, who have the largest
exposure to coal ash toxins are typically rural, poor, and
minority populations (now defined as special populations)
Coal ash
http://clclt.com/theclog/archives/201
0/08/03/dems-may-have-lost-theirminds-over-coal-ash-regulation
http://appvoices.org/2013/10/08/courtto-epa-get-moving-on-coal-ash/
Nuclear
• Reactor breaches due to technical problems
(Chernobyl, 1986), natural disasters
(Fukushima, 2011)
• Disposal of nuclear waste
• Common misconception: Which is more
dangerous? Waste that is highly radioactive,
or not-so highly radioactive?
• There is currently no central repository for
storage of nuclear waste in the U.S.
– Discussion: Pros and cons of a central storage
facility
Renewable energy sources
• Hydropower
– Ecosystem changes (water temperature, chemistry,
flow rate)
– China’s Three Gorges Dam (2012): Flooded
archaeological sites, displaced 1.3 M people,
increased risk of landslides
• Wind and solar
– Land must be cleared
– Wind turbines and solar towers have a visual impact
on landscape and kill birds
– Some materials such as lubricating oils (wind) and
heat transfer fluids (solar) are toxic.
Electricity distribution
• Power lines impact visual landscape and require modifications
to the environment (keeping trees pruned back).
• Underground power lines are more expensive and may have
no less impact.
www.nesec.org
theboweryboys.blogspot.c
9/29
• Complete the table
Pro
con
Wind
solar
Fossil fuel
Hydroelectricity
Nuclear
• Last week we looked at different ways
electricity can be generated. What do you
think happens after electricity is generated?
Electric Grid uses Transformers
• Voltage generated in power stations is stepped up
with transformers prior to being transferred across
the country by overhead cables.
• Then other transformers reduce the voltage before
supplying it to homes, offices, and factories.
• Last week we looked at different ways
electricity can be generated. What do you
think happens after electricity is generated?
The Transformer—Boosting or
Lowering Voltage
• input coil of wire —primary powered by AC voltage source
• output coil of wire —secondary connected to external circuit
The Transformer
Transformer (continued)
• both wound on a common iron core
• then magnetic field of primary passes through secondary
• uses ac in one coil to induce ac in second coil
The Transformer
• Transformer relationship:
primary voltage
secondary voltage
=
number of primary turns
number of secondary turns
• Vp / NP = Vs / Ns
Transformers Everywhere
• This common
transformer lowers
120V to 6V or 9V. It also
converts AC to DC by
means of a diode inside.
• A common
neighborhood
transformer that
typically steps 2400V
down to 240V.
Electric Grid uses Transformers
• Voltage generated in power stations is stepped up
with transformers prior to being transferred across
the country by overhead cables.
• Then other transformers reduce the voltage before
supplying it to homes, offices, and factories.
Transformer Power
• Neglecting heat losses, power into a
transformer = power out of transformer.
Voltage
x current primary  Voltage x current secondary
Electric Power
• Electric power is equal to the product of the
voltage and current.
• P=I * V
Electric Power  Voltage  current
• Fill out known measurements
• Find equations where there is only one
variable missing
• Solve for unknowns
• Number of coils = number of turns
• VAC = volts
• I kw = 1000 watt
Benchmark
assessment
friday
9/30
• A primary coil has 100 turns and has a voltage
of 120 volts, how many volts would go
through the secondary coil if it has 10 turns?
• How well do you understand your
transformers worksheet?
• Use the formula sheet to create a definition of
electric potential.
• (I) Electric current – a flow of electrons,
measured in amperes (amps).
• (V) Electric potential – potential difference
per charge. Measured in volts
• (R) – resistance – - ability to resist the flow
of electrons, measured in ohms
10/1
1. Think about V=I*R, what happens to the
resistance as the current goes up?
2. What happened to the current of the circuit
as more bulbs are added in series, in parallel?
3. What happens to the resistance of the
circuit as more bulbs are added in series? In
parallel?
Total resistance of resistors in series : R = R1 +
R2 + R 3 +
A series circuit is shown in the diagram above. The total resistance
is the sum of the individual resisters.
The current flows through each resistor in turn. If the values of the
three resistors are 10, 20 and 30, what is the total resistance?
Key idea: What happens to the total current of the circuit as more
resisters are added in series?
A series circuit is shown in the diagram above. The total resistance
is the sum of the individual resisters.
Key idea: What happens to the total current of the circuit as more
resisters are added in series?
In a series circuit – as more resisters are
added the current goes down and the
resistance goes up
With a 10 V battery and the total
resistance is 20.
by V = I R the total current in the
circuit is:
I = V / R = 10 / 20 = 0.5 A.
The current through each resistor
would be 0.5 A
Parallel circuits
• The total resistance of a set of resistors in parallel is found by
adding up the reciprocals of the resistance values, and then
taking the reciprocal of the total:
• equivalent resistance of resistors in parallel:
• 1 / R = 1 / R1 + 1 / R2 + 1 / R3 +...
What happens to the current of the
parallel circuit as more resisters are
added?
Parallel circuits
• The total resistance of a set of resistors in parallel is found by
adding up the reciprocals of the resistance values, and then
taking the reciprocal of the total:
• equivalent resistance of resistors in parallel:
What happens to the current of the
parallel circuit as more resisters are
added?
As more resisters are
added in parallel the
current across the battery
increases and the
resistance decreases,
think about the splits.
Series parallel analogy
• Usually when I drive down the road I notice
the more cars that are on the road, the slower
traffic goes. Create an analogy to explain
current, resistance, series and parallel based
on this analogy.
• Does this analogy break down at any point?
• Voltage drops – voltage is going to be the
same as the source across each branch of
the parallel.
• In series – the voltage is shared in each of
the bulbs.
• If the battery voltage is 6, in series the
voltage drop is 2v each, in parallel the
voltage drop is 6 v each
Exit slip
Using V= I *R
• The current above has a 10 volt power source. The
value of the resisters are
r1= 1, r2= 5, r3= 10
1. What is the current across each resister?
2. What is the total current?
3. What is the complete resistance?
4. What is the power going through the battery?
With a 10 V battery, by V = I R the
total current in the circuit is: I = V /
R = 10 / 2 = 5 A.
The individual currents can also be
found using I = V / R. The voltage
across each resistor is 10 V, so:
I1 = 10 / 8 = 1.25 A I2 = 10 / 8 =
1.25 A I3=10 / 4 = 2.5 A
35.6 Combining Resistors in a Compound
Circuit
The equivalent resistance for a pair of equal resistors in parallel is
half the value of either resistor.
The equivalent resistance for a pair of 1-ohm resistors in parallel
is 0.5 ohm.
The equivalent resistance is less because the current has “twice
the path width” when it takes the parallel path.
35.6 Combining Resistors in a Compound
Circuit
a.
The equivalent resistance of two 8-ohm resistors in series is
16 ohms.
35.6 Combining Resistors in a Compound
Circuit
a.
b.
The equivalent resistance of two 8-ohm resistors in series is
16 ohms.
The equivalent resistance of two 8-ohm resistors in parallel is
4 ohms.
What causes lightning?
• http://www.youtube
.com/watch?v=RLWI
BrweSU8
• What comes to mind when you think of
lightning?
• Are you safe in a car during a lightning
storm?
• How is electric potential related to an
electric current?
bulbs
• Why doesn’t a 1.5 volt battery power your
car?
• Why doesn’t a 1.5 volt battery power a 6 volt
computer motor?
• a 12 volt motor V=6, v=1.5 say the resistance
is 1 ohm. Lets solve for current for each
battery. I = v/r. The current for the 6 volt
would be 6/1= 6 amp. The current for the 1.5
would be 1.5/1 = 1.5. one.
• What are
three things
needed to
generate
electricity?