Transcript Lesson 1 Electricity

ES Lesson 1:
What is the science of electricity?
•
•
•
•
•
What is science?
What is electricity?
How is electricity made and distributed?
What is a fuse? What is a circuit breaker?
How can household electricity hurt us if we don’t
understand how it works?
© 2012 C. Rightmyer, Licensed under The MIT OSI License, 20 July 2012
Jake has a hypothesis: He thinks eating
mushrooms will help him grow more hair.
• What is the scientific method and
how could he use it to prove or
disprove his theory?
–
–
–
–
–
Observation (and research)
Hypothesis (or theory)
Predicting expected test results
Designing and conducing tests
Making conclusions from the test
results
• How could we design a test to see if
Jake’s theory is correct?
Jake lived 1.5 million years ago. How do archeologist know that?
Early Greek philosophers used logic and thought
to explain life. The scientific method came later.
• Thales of Miletus (582 BC) suggested
that water is the basic substance of life.
• Anaximenes of Miletus (535 BC)
counters that air is the fundamental
substance.
• Empedocles of Acragas (445) suggests
there are four different fundamental
elements: earth, air, water, fire
• Leucippus of Miletus (435 BC)
proposes that the basic elements are
tiny corpuscles that he called “atoms” - meaning indivisible. He was on the
right track but did not have adequate
methods for testing his theory.
Http://realscience.breckschool.org/upper/fruen/files/Enrichmentarticles/files/History.html
In 150 AD, Ptolemy constructed a working model of our solar system.
• This model was well accepted by
scientists and religious leaders of
his day.
• His model was useful for
developing time keeping and
navigation methods.
• But, his model incorrectly
assumed our earth as the center of
the universe.
http://en.wikipedia.org/wiki/File:EB1711_Armillary_Sphere.png
Copernicus publishes a new heliocentric
theory of planetary revolution (1543 AD)
• It took more than 200 years for
the scientific community to
agree that Copernicus was
correct. Why?
• If true…..
– What could possibly make our
heavy earth move?
– The universe must be vast beyond
belief.
– Distant stars must be impossibly
large.
Http://en.wikipedia.org/wiki/Nicolaus_Copernicus
Http://www.ScientificAmerican.com/ (Jan 2014)
1910 Ford Model R
Note: this automobile has been beautifully restored.
By 1910, you wouldn’t see power poles or a parking lot.
What are some electricity powered devices
that we take for granted today?
•
•
•
•
•
•
•
•
•
Ovens, cooktops, toasters
Microwave ovens
Electric blankets
Radiant heaters
Lights
Dishwashers
Refrigerators
Vacuum cleaners
Televisions, radios,
stereos
•
•
•
•
•
•
•
•
•
•
Clocks
Drills, saws, air compressors
Electric motors/cars
Batteries and battery chargers
3-D printers
X-ray machines
Thermostats
Computers/pads
Smart phones
Irrigation systems
Only 105 years ago, how did people live without electricity? For
instance, how did they:
• Cook food and stay warm.
• Read books at night.
• Obtain drinking and bathing water. (Could you
shower?)
• Go to the toilet.
• Save perishable food.
• Clean the floors and rugs.
• Communicate with neighbors and friends.
• Get the news.
• Make wood and metal products.
• Do math problems.
• Know the time of day.
• Make beer, wine, and Manhattans.
(Who knows what mead is and what it’s made of?)
What is electricity?
• Electricity is a handy form of energy that we can use for
doing work.
– Electricity generators create an electromagnetic force.
– This force causes electrons to flow through conductive
materials.
– Kinetic energy from the flowing electrons is consumed
by electric devices (lightbulbs, motors, and such) in
order to do work for us.
There are two types of electricity that we will
learn about in this course.
(1) Alternating Current (AC)
electricity. The kind that we get
from the power grid.
(2) Direct Current (DC) electricity.
The kind that we get from a
battery or an AC/DC adapter.
Where is AC electricity made and how is it delivered to us?
Electricity and Magnetism, Gareth Stevens Publishing, Steve Parker, 2007
ES demo 1-1. A steam driven reciprocating AC power generating plant
BE demo 1-1
A scale model of James Watt’s steam powered electric generator
A steam turbine rotor
Picture of a modern AC power generator.
Picture of a modern AC power generator.
http://www.mpoweruk.com/steam_turbines.htm
Ever wonder how you replace a power pole?
It’s a tricky job installing a new transformer!
How does AC electricity get from the power
lines into our homes?
Wires from the power lines
Main breaker box
ES demo 1-2. Main breaker box with its outside cover is open
BE demo 1-2
Whole house shut off
switch
Individual circuit
breaker switches
ES demo 1-3. View of circuit breakers behind the inside cover.
BE demo 1-3
ES demo 1-4. A surprising demonstration of electrical
power delivery to your wall outlet.
BE demo 1-4
What happens if we connect the lightbulb’s
white wire to the green wire.
“Accidentally” connect the black wire to the
white wire and see what happens.
ES demo 1-5. How a fuse works.
A few strands of steel
wool
Two D-cell
batteries in series
Desk protector
Alligator clip
wires.
Gateways School, Lewis Camp, 2009
(Possibly from Teching Electricity, Yes You Can, Scholastic Professional Books, )
What if you accidentally touched both the black
and white wires to your body?
Cook a vienna sausage with a pair of open
electrical wires. The sausage smokes and turns
black where the wires are attached. Many kids
want to eat it afterwards, but since this is a
school situation rather than a campsite, I just
toss it in the trash can.
ES project 1-6. Measure AC Voltage using a multimeter
BE proj 1-8
-
Multimeter
(Volts AC)
+
~
-
AC Voltage
Symbol
+
What can happen without a ground wire?
The ground wire protects against a short circuit
What have we learned so far?
•
Electricity is a portable and useful form of energy that we can use to do
work.
•
Electricity consists Voltage and Current.
–
–
Voltage is the measure of electromagnetic force that can cause electrons to flow through
wires and electronic devices.
Amperes is the measure of electron flow, called current, that provides energy used by
electronic devices. The term Amperes is usually abbreviated as Amps.
•
Most AC type electricity is generated at a power plant and delivered to
electrical outlets by way of a distribution grid. This grid consists of
transformers and wires.
•
Because our bodies are good electrical conductors, accidental contact with
conducting wires can shock or burn you. Accidents are much more likely
if you do not understand how AC electricity works.
What if you accidentally touched both the black
and white wires to your body?