Download File - Shaw STEM Lab

Electrical Circuits featuring Snap Circuits
Getting Started with Electricity – Level 1
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What You’ll Learn…
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What electricity is and how to control it
The four basic elements of a circuit
The difference between AC and DC current
What transformers are and how they are used
Safety tips for working with electricity
How to identify and avoid dangerous short circuits
Proper care of fragile and delicate electrical equipment
How to design simple circuits using Snap Circuits
How electrochemical batteries work
How to build and use a continuity test circuit
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Rewrite and answer the following questions in your
Word Document. Ensure you save this document to
your group’s file.
1. Define electricity.
2. What is Lightning?
3. What are the atoms that are positively and negatively charged called?
4.What do AC and DC stand for? Why are they named these?
5. Name the two types of electrical circuits?
6. How many cycles per second does AC voltage alternate?
7. What is a transformer used for?
8. What is a conductor(in electricity)?
9. What is an insulator?
10. How many volts in household current?
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What You Should Know…
What is electricity?
Electricity is simply the flow of electrical power or charge. There
are different forms of electricity. You’ve almost certainly experienced
static electricity after walking on a carpet and touching a door knob.
That shock you felt was a flow of charged particles from your finger
to the door knob. Lightning is an extreme form of static electricity
caused by the build up of charged particles in rapidly moving air
currents.
As you probably know, atoms have positively charged particles
called protons and negatively charged particles called electrons.
Both carry an electrical charge. It’s relatively easy to dislodge
electrons from the outer orbit of an atom in certain substances like
copper wire. Such substances are called conductors. When that
happens, the atom’s charge is out of balance and it attracts another
electron. This flow of electrons is the electricity we use to power our
homes and appliances.
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What You Should Know…
Electrical energy flows in wires like water in pipes…
Similar to a stream of water though a hose, electricity is a stream
of electrons flowing in a conductive wire. It flows when
electrical pressure is applied to the wire. We call that electrical
pressure voltage.
The flow of electrons starts
with a generator and travels
through wires to the point
where it is consumed
Gravity
Pressure
(force)
Nozzle
(Resistance)
Flow
Control
Valve
The resistance in this
heater consumes electrical
energy as it converts the
electricity to heat and light.
Smaller Pipe
(Resistance)
Flow Volume in
Gallons per Minute
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What You Should Know…
Basic Two Types of Circuits:
Parallel and Series
All circuits, whether
they be electrical,
pneumatic, hydraulic
or the plumbing pipes
in your home water
system have these
FOUR things in
COMMON…
They all have an energy
source, a path that the
energy follows, flow
control devices, and a
load that consumes the
energy.
1
Energy Source
Outlets
Batteries
3
Air
Compressor
Flow Control
Devices
Switches
Valves
2
Wires
4
Lights
Path
Tubing
Load
Cylinders
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What You Should Know…
All your
experimental
circuits will use
DC current.
Evolution of AC and DC electrical currents…
There are two types of electrical currents –
AC (Alternating Current) and DC (Direct Current).
Thomas Edison was a supporter of DC current, so he
built DC power stations in many major cities in the late
1800’s. But DC power had one major limitation –
power plants could only send DC electricity about one
mile before the electricity began to lose power.
DC current
flows in one
continuous
direction.
DC Circuit
In 1896, George Westinghouse introduced a highvoltage alternating current (AC) transmission line from
his Niagara Falls hydroelectric plant to Buffalo New
York, 20 miles away. This project established the
common practice of locating electric generating plants
long distances from the end consumer.
AC current
alternates
Study the two animations on this page carefully to see
its
the difference in the direction the current is flowing in
direction
the top DC circuit and the bottom AC circuit.
60 times
every
second.
Source: PBS Online – AC/DC: What's the Difference?
AC Circuit
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What You Should Know…
Understanding AC – Alternating Current…
AC stands for alternating current because
it alternates its polarity from positive to
negative at a rate of 60 cycles per second
in the USA, which can be visualized as a
sine wave. The electricity coming out of
the wall outlets in your home is AC.
AC generators are
like electric motors in
reverse - they
produce electricity
instead of use it!
AC
Generator
+
-
Sine Wave
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What You Should Know…
Understanding DC – Direct Current…
DC stands for direct current because
it only flows in one direction. DC
current from solar photovoltaic panels
and wind turbines can be stored in
batteries for later use.
Electrochemical batteries are
manufactured with the ability to
provide DC power that is chemically
produced inside the battery cells.
Direct Current
Power Adaptors
transform
electrical energy
Power adapters on electronic devices
like computers, camcorders and many
other devices in your SmartLab
convert AC power from the wall socket
into DC power for the device.
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What You Should Know…
The benefits of DC – Direct Current…
Portability!
How many battery powered
devices do you have with you
right now?
Batteries
They are all using DC power!
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What You Should Know…
The battle of the currents continues today…
While the vast majority of our bulk electricity is still
being transmitted and delivered as AC current, modern
technologies have enabled DC current to make
somewhat of a comeback in the world.
Do an online search for “High-voltage Direct Current”
(HVDC) and you will find that high-voltage DC electric
power transmission systems are being built today.
Vs.
Edison
Westinghouse
1000 KV HVDC Transmission Lines in US
At the time of Thomas Edison, DC power could not be
economically transmitted long distances. But now some
experts are saying that long-distance HVDC systems
are less expensive and suffer lower electrical losses.
The technology that makes HVDC transmission
possible was developed in Sweden in the 1930s.
The longest HVDC link in the world is currently a 600
MW link 1,100 miles long called the Inga-Shaba in the
Democratic Republic of Congo.
1100 mile HVDC Transmission Line, Congo
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What You Should Know…
Transformers can change the voltage…
Transmitting electrical power over
long distances, like from large
electrical power stations to your
home, requires very high voltages.
Most of these high-voltage
transmission lines carry between
138,000 to 765,000 volts. Very
dangerous!!!
Transformers are used to reduced
the voltage before it enters homes
and businesses.
Electrical transformers change the voltage
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What You Should Know…
Transformers can change the voltage…
The ability to change and transform electrical
energy is one of the characteristics that makes
electricity such a popular form of energy.
The induction coil in cars raises the 12 volts
coming from the battery to the 15,000-20,000
volts needed to produce a good ignition spark
in the spark plugs.
Spark
Plug
Ignition
Coil
12 Volt
Battery
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What You Should Know…
Transformers can change current too…
Many electronic devices need a lower
voltage than you get from a 120 volt AC
wall socket, and sometimes they also
need DC current instead of AC. That’s
why you see a lot of small transformers
called power adapters in your
120 volts
SmartLab and at home.
AC Input
A power
adapter is a
transformer.
Your SmartLab electricity kit can be
powered by AA batteries or by
connecting a power adapter that
transforms 120 volts AC into 5 volts DC.
12 volts
DC Output
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Caution!
Safety first…Be sure you read these safety points!
Fortunately, none of the electronic components in your Tronix kit carry
enough power to be dangerous. But that might not always be the case with
electrical circuits you might encounter elsewhere.
So when you are working with electricity, it’s always a good idea
to develop safe work habits.
 NEVER touch loose wires unless you are SURE
they are disconnected from a power source.
 ALWAYS make sure that power is switched OFF
when making changes to an electrical circuit.
 If in doubt, ask for HELP from a knowledgeable
responsible person. Better safe than sorry!
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Caution!
Proper care of delicate electronic equipment…
Some things you will work with in the SmartLab are STRONG and TOUGH.
But electronic equipment is fragile and delicate by nature, because the
wires are very small and easy to break.
So how should you treat them?
Electronic components are fragile,
handle them with care!
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Caution!
How to avoid a short in your circuit…
Short Circuit – a “short” in a circuit occurs when an alternate path (with less resistance) to the
intended path is introduced. A path with no resistance allows too much current to flow. If the location
of the short in a circuit only partially reduces resistance, it’s called a minor short. Minor shorts will
typically disable a component in your circuit. If the location of a short eliminates all resistance, that’s
called a dead short. Circuits with a dead short quickly melt or burn something up!
The electrical opposite of a short circuit is an "open circuit", which happens when a wire is broken or
missing so that no current can flow. Open circuits cannot operate but they do not damage anything
like a short circuit does.
Red wires
should NOT
be there
because they
cause a short
circuit.
Shorts usually
occur when
someone puts
an extra wire
in the circuit.
Dead Short
Minor Short
A minor short just disables
one component, but a dead
short burns something up!
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The GREEN circle indicates DC
power
The BLUE circle indicates AC
power
Set the MultiMeter on 20
DC
The RED circle
How to set up the
MultiMeter
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First Activity, test batteries…
Here’s What You Do-Check out the Voltage Kit from Mr.
Ochs
1. Identify the following parts on the digital multi-meter AC
voltage, DC voltage, resistance, continuity, DC amperage,
and AC amperage.
2. Learn to measure and compare the voltages of the
various batteries in your collection. Make a simple chart
or table in WORD to record your findings. List the
advertised voltage in the second column of your data chart
and the actual measured voltage in the third column.
a. Make sure the DMM is set to measure DC voltage.
b. Touch the red lead to the positive end of the battery and
the black lead to the negative end of the battery. What
voltage do you get? Write it in your chart.
c. Repeat this process with each of your batteries until you
have tested them all, and be sure to write your test results
in your data chart.
Battery
To be
tested
Advertised
Voltage
Measured
Voltage
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Next with EDISON
Look for the software in Quick Access…
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Start with EDISON
Create a circuit for each of the schematics on the
right…Take a picture and Label them.
Battery
Light
Series Circuit
Push
Switch
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Start with EDISON
Create a circuit for each schematic
on the right…Label them
Parallel Circuit
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Stuff You’ll Need …
This is some of the Snap Circuits basic electricity collection you’ll
need…
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Caution!
How to properly install your AA batteries…
You must make sure you insert the AA
batteries correctly or it will melt the battery
case and ruin it. The negative end goes
against the spring.
Opposite
ends?
Your batteries should face
opposite directions like these.
Batteries should never get warm!
Like this…
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Build your circuits on the clear board with
the little holes even though we do not
show the clear board in many of the
slides that follow.
Do It!
What’s a schematic…?
You’re ready to get started making actual
circuits, but before you can start you need a
clear board and the snaps.
Switch
Switch
Battery
Battery
Lights
Lights
Schematic – A schematic is a simplified graphic representation of a circuit using lines and
symbols rather than actual pictures of the electrical components and wires. You should learn to
read the schematic drawings like the ones above, and you should learn to sketch simple
schematics of your own circuits.
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Do It!
Simple electrical Series and Parallel circuits…
Use these parts to create your first
simple circuit using the schematic
drawing below. Then wire the
previous circuits with up to three
bulbs, in series and parallel,
document.
Lamp Holder
Battery
Push
Switch
Light
This circuit has only one path
for the electricity to follow.
Push-Button Switch
Put these components on
the clear board and use
the snaps to connect the
battery (-) to the switch, the
switch to the light, and the
light to the battery (+).
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Do It!
Simple electrical circuits…
Your first circuit was pretty easy wasn’t it.
So what kind of switch is a push-button
switch? Does the light stay on when you
let go of the button? Can you think of any
switches in your house that work like this?
This type of switch is called a momentary
switch. It’s only on for the moment that
you are pressing the button. Your
doorbell works like that, right?
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Do It!
How electrochemical batteries work…
Why does electricity follow the path of wires?
Why doesn’t it just go wherever it wants or why
doesn’t it just sit there and do nothing?
A battery has a positive side and a negative
side. The inside of a battery is made up of
layers of special materials and chemicals.
What makes electricity move at all?
The materials connected to the negative side
of the battery have surplus electrons that
they want to get rid of.
Earlier you learned that electricity is the energy
produced by the FLOW of ELECTRONS. So
what makes the electrons start flowing?
Well, the answer is PRESSURE. We call this
pressure VOLTAGE. In the case of batteries, this
pressure or voltage is created because of a
chemical imbalance that exists in the battery.
The materials connected to the positive side
are electron deficient, so they are wanting to
get more electrons.
How can we get
these two sides
of the battery
together?
Let’s discuss a simple analogy to help you
understand how a battery works, which will also
help you answer the other questions above.
Surplus
Electrons
Needs
Electrons
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Do It!
Conductors versus Insulators…
Why can’t the surplus electrons from the
negative side get over to the positive side?
They can’t get there because they need a
conductive path. The air gap between the
negative pole and the positive pole is preventing
them from crossing over. They need a path
made of a material that conducts electricity.
Some materials conduct electricity
(conductors) and others resist the flow of
electricity (insulators). Your challenge is to
find out which types of material are good
conductors and which are insulators. You
can build a simple test circuit as shown here
and on the next slide to test the conductivity
of a variety of different materials.
Light
Test
Materials
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Do It!
Building a continuity tester…
Electricians usually use a digital multimeter to
test the conductivity (the ability to conduct
electricity) of wires that might be damaged.
But you are building your own conductivity tester
as you see here. Touch the loose wires to each
of the materials you are testing. If the light comes
ON, the test material is a conductor. If the light
stays OFF, the material is an insulator.
Item
Conductor or
Insulator
1. Rock
2. Graphite
3. Copper (Penny)
Which of these materials will conduct
electricity? You can use materials like those
below or any other materials you can test.
Ask Mr. Ochs for these materials!
4. Spoon
5. Paper
6. Wood
7. Paper Clip
8. Other
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Do It!
How electrochemical batteries work…
Now that you know the types of materials that
conduct electricity… you could provide a path
for the electrons to flow from the negative side of
the battery through a light to the positive side.
Voltage
Time
New Battery
Eventually though, the battery will be dead and the
light will go out. How and why does that happen?
In the beginning there was an imbalance between
the negative and positive sides of the battery, which
created the potential for energy to flow. But now
they are balanced, so the electrons quit flowing and
you have no current. The voltage from your battery
will gradually decrease until it is completely dead.
Dead Battery
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