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Dr. M. H. Suckley & Mr. P. A. KlozikEmail: [email protected]
I. Static ElectricityII. Current ElectricityIII. Applications
ElectricityI. Static Electricity
A. Teaching Static Electricity - Naive Ideas
B. Wonderment of Producing Static Charge
1. Rubbing a. The Fluttering Butterfly . . . . . . . . . . . . . . . . . . . . . . . 5
b. The Static Mystery . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Contact a. Fickle Friends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
b. The Repulsive Ball . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Induction a. Dancing Spheres in Captivity . . . . . . . . . . . . . . . . . . 9
b. The Attractive Yard Stick, Broom, and 2 X 4’s. . . . 10
ElectricityI. Static Electricity
C. Explanations - Developing A Model
1. How Do Materials Become Charged?. . . . . . . . . . . . . . . . . . . . 11
2. Using The Model To Illustrate the Static Charge? . . . . . . . . . 12
3. Developing the Laws of Static Electricity
a. Golf Tubs and Test Tubes. . . . . . . . . . . . . . . . . . . . . . . . . . . 13
b. Sticky Tape Static Charges . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. The Electrostatic Series. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
a. Where Should We Put Scotch Tape In The Series?. . . . . . . . 16
b. Attractive Stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
D. Applying the "Model" For Static Electricity
1. The Moving Soda Can, Ping Pong Ball, or Loony Loop. . . . . . 18
2. Groovy Record. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3. Electrophorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4. Electrostatic Doorbell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5. The Van De Graff Generator
6. Static Charges Can Kill You
Electricity
II. Flowing or Current Electricity A. Teaching Current Electricity - Naive Ideas . . . . . . . . . . . . . 22
B. Wonderment of Current Electricity. . . . . . . . . . . . . . . . . . . . Static – Alternating and Direct Electricity
C. Building The "Simply Super" Circuit Board . . . . . . . . . . . 23
D. Parallel Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
E. Series Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
F. Combined Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
G. Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
H. Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
I. Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
J. Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Electricity
III. Application of Electricity
A. Buzzer Door Bell
B. Chime Door Bell
C. Speaker
D. Christmas Lights
E. Toaster
F. Light Bulb
G. Hair Dryer
We Had A Great Time
Acceptance of a New Concept
A widely accepted way to explain how learners adopt new understandings of phenomena is presented in the Conceptual Change Model (CCM)*.
There are two major components to the Conceptual Change Model.
The first component are the conditions that need to be met in order for a person to adopt a new understanding. There are three conditions leading to the adoption of a new concept. A learner has to: (1) become dissatisfied with their existing concept, (2) find the new concept intelligible, (3) find the new concept plausible and fruitful.
The second component of the CCM is described as the status of the new concept. A concept has status when it meets any of the conditions indicated; however, the more conditions that the new concept meets, the higher the status the new concept obtains, and hence, a higher probability of being adopted.
References *Posner, G.J., K.A. Strike, P.W. Hewson, and W.A. Gertzog. 1982. Accommodation of a scientific conception: Toward a theory of conceptual change. Science Education 66: 211-27.7
NSTA Board Adopts New Position Statement on Laboratory Science
The NSTA Board of Directors has adopted a new position statement which reaffirms the
central role laboratory investigations play in quality science instruction. “for science to
be taught properly and effectively, labs must be an integral part of the
science curriculum.” The new statement replaces Laboratory Science, which was
adopted in 1990.
Static Electricity
1. After a material acquires a positive charge, it has more positive charges (protons) than it did.
2. When a material has positive charge, the missing negative charges (electrons) have been destroyed.
3. Whenever a material becomes charged, the charges have been newly created in the process.
4. Positively charged atoms give a positive charge; negatively charged atoms give a negative charge.
5. Static electric forces are always attractive.
6. In order for an object to act like it is charged, electrons must be added or removed.
7. All wires must be coated with an insulating material or the electricity will leak out.
I. Naïve Ideas
7
Grade Level Appropriate Concepts
K-4: Pushing or pulling can change the position and motion of
objects. (Electric forces can be used as a source of the
push or pull). Students will indicate that magnetism, gravity
and electrical charge can exert forces on objects without
touching the objects.
2
Grade Level Appropriate Concepts
5-8: Unbalanced forces cause changes in an object’s
motion. (An imbalance in charges on an object results in an
unbalanced force, causing nearby uncharged objects to be
attracted). Students will recognize different forces and describe
their effects as magnetic, gravitational, electrical or nuclear
forces
1
Grade Level Appropriate Concepts
9-12: The electric force is a universal force that exists between any
two charged objects. Opposite charges attract while like
charges repel. The strength of the force is proportional to the
charges and, as with gravitation, inversely proportional to the
square of the distance between them. Between any two
charged particles, electric force is vastly greater than the
gravitational force. Most observable forces such as those
exerted by a coiled spring or friction may be traced to electric
forces acting between atoms and molecules. Students will
identify the characteristics and relative strengths of magnetic,
gravitational, electrical and nuclear forces. Then they will
analyze the relationship between them.
0
Rubbing - The Fluttering Butterfly
Rubbing - The Static Mystery
1 2
Contact - The Fickle Friends
Contact - The Repulsive Ball
Induction - Dancing Spheres In Captivity
Induction - The Attractive Yard Stick, and 2 X 4
Models - How Materials Become Charged OR Learning to Classify based upon Physical Properties
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Rubbing Contact Induction
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Models - How Materials Become Charged
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Rubbing
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After Rubbing one Material has more and the other has fewer electrons.
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Contact
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1
Models - How Materials Become Charged
2
After Touching one Material has more and the other has fewer electrons.
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Induction
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0
Models - How Materials Become Charged
2
When a material with an excess of electrons is moved near a material without an excess of electrons the electrons within the uncharged material move producing charged areas. When the material with an excess of electrons is removed the electrons return to their original positions
Developing The Laws Of Static Electricity Golf Tubes and Test Tubes
Developing The Laws Of Static Electricity
Sticky Tape Static Charges
Electrostatic Series
Materials tend to gain electrons and become Negatively Charged
Materials tend to lose electrons and becomePositively Charged
Hard RubberCombVinyl (PVC) - Golf TubeRubber BalloonPlasticPolyethyleneReynolds or Saran WrapStyreneAmberLuciteWoodSteel CottonPaperSilkCat’s FurWoolNylonHuman hair GlassRabbit’s Fur
Electrostatic SeriesWhere Should We Put Scotch Tape In The Series?
Substance Does the Scotch Tape
Attract or Repel?
Charge On:
Tape Substance
Transparency
Comb
Rubber Balloon
Plastic
Wood
Cotton
Paper
Silk
Wool
Nylon
Glass
Models - Electrostatic Series
Attractive Stuff
Applying the "Model" For Static Electricity
The Moving Soda Can
Attractive Ping Pong Ball
Loony Loop
2
Applying the "Model" For Static Electricity
Groovy Record
1
Lightning rods were originally developed by Benjamin Franklin. A lightning rod is very simple -- it's a pointed metal rod attached to the roof of a building. It connects to a piece of copper or aluminum wire that's connected to the ground.
The lightning rod provides a low-resistance path to ground that can be used to conduct the enormous electrical currents when lightning strikes occur. 0
Lightning Rods
Applying the "Model" For Static ElectricityElectrophorus \i-lek-'traf--rs\
2. Rub the Styrofoam with the wool.
3. Lower the cake pan NEAR the Styrofoam sheet.
4. Touch the cake pan with your fingertip.
5. Lift the cake pan away from the sheet.
6. Touch the cake pan again.
7. Repeat the procedure several times without re-rubbing the sheet. You will obtain the same results each time.
8. Repeat steps 2-5. Hold a neon bulb by one wire and touch the other wire to the charged pan.
9. The filament, of the light bulb, that lights first indicates the direction of the electron movement, (negative to ground).
Applying the "Model" For Static Electricity
Grounded
Grounded
Insulated
Insulated
Charged
Charged
Charged
Static Electric Doorbell
Transparency
How a Van De Graff Works
2
Students and Van De Graff
1
Pie Pans and Van De Graff
0
Static Fires
Static electricity caused the fire that damaged this car. The Petroleum Institute has researched 150 cases of these fires. Their suggestions indicate that you should NEVER get back into your vehicle while filling it with gas. If you absolutely HAVE to get in your vehicle while the gas is pumping, make sure you get out, close the door and touch the metal, before you ever pull the nozzle out. This way the static from your body will be discharged before you ever remove the nozzle.
Current Electricity
1. Electrical energy flows from source to converter (light bulb, heater, etc.) by connecting a single wire.
2. If two wires are needed, energy flows from the source to the converter through both wires
3. In a circuit with electrical devices, more electrons leave the source than return to it.
4. Electrons are destroyed or “used by” the converter (light bulb, heater, appliance, etc.).
5. The electrons that comprise an electric current come from the source. (A dry cell is a can full of electrons. When it is out of electrons, we throw it away or recharge it..)
6. Every part of a circuit gets the same current.
7. You can connect as many light bulbs, appliances, etc. in a circuit without affecting their
behavior.
8. To receive more light from a bulb, you need a different light bulb.
9. Adding batteries to a circuit always increases the current (brighter lamps, faster motors, etc.).
10. All materials that conduct electricity conduct equally well.
11. Water is a good conductor. . . . . .
I. Naïve Ideas
11
AC/DC Demonstrators
2
ALTERNATING CURRENT:
DIRECT CURRENT:
1
Direct and Alternating Current
30
No Current
Direct Current
Alternating Current - Blinking
Alternating Current – Solid light
Example Prices for Circuit Boards
AP6302 Simple Circuits Kit $37.10
15934W2 Circuit Board $19.95 14718W2. Standard flashlight bulb $3.25 Pk. Of 10
Total Cost $21.00
Simple Circuits Kit AP6302
Each for $43.05
AP6302 Simple Circuits Kit
$37.10
Average Price of Commercially made Circuit Board
$84.00 - each
4
Building the Simple Circuit Board - Materials
1. 7 - Magnets
2. 1 – Simple Circuit Card
3. 7 – Sticky Dots
4. 3 – Lamp Units
5. 12 – Paper Clip
6. 1 – Diode
7. 3 – 10 Ohm Resistors
8. Toothpick
9. Steel wool for Fuse
10. Red and Black Wire for Battery Connection
10
The Power Supply
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
The power supply can be any 6-volt DC source. This could be 4 AA batteries, a lantern battery or a transformer. We are using a battery pack obtained from a Polaroid film pack.
Building the Simple Circuit Board - Battery
Step 1: Wrap wire onto paperclips making two leads
Step 2: Insert Paperclip Leads into Battery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
Building the Simple Circuit Board – The Simple Circuit Board
Parallel Circuit
Series Circuit
Combined Circuit
Building the Simple Circuit Board – Circuit Board Lamps
Bend Paperclip 90 Degrees
Two Bent Paperclips and Light Bulb
Completed Lamp Unit
Heat Shrink Tubing
Wire Wrapped Around P.C.
Christmas Light bulb
Multimeters
Amperage Voltage
Building the Simple Circuit Board - Magnets
1. Place Glue Dot on Back of Magnet.
2. Place Magnet on Circuit Board.
1
Building the Simple Circuit Board – Completed Parallel Circuit
1. Place Paperclips as Indicated.
2. Attach Lamp Units.
3. Attach Power Supply.
3
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
Qualitative Characteristics of Electricity
1. Connect the battery and observe the lights. (number lit and brightness)
2. Describe the effect of moving bulb unit 1 just enough to break the circuit of the rest of the bulbs.
3. Describe the effect of moving bulb unit 2 just enough to break the circuit of the rest of the bulbs.
Quantative Characteristics of Electricity
1. Volts - Pressure that cause the current to flow. The potential difference across a conductor in an electric field
2. Amperes - Rate of the current flow. One ampere is approximately equivalent to 6.24150948×1018 electrons moving past a boundary in one second.
3. Ohms - Resistance of the conductor (wire or hose) to the flow. A device has a resistance of one ohm if one volt causes a current of one ampere to flow.
4. Watts - Power produced due to the pressure and the flow of the electrons.
4
1b - 1a
Parallel Circuits - Obtaining Voltage Data
3
1b - 2a 1b - 3a 1a - Master
Parallel Circuit – Voltage Data
5
Circuit Simulator
4.3Master - 1a 3(1+2+3)
4.31b – 2b 2(1+2)
4.31b – 1a 1 (1)
VoltagePlacement of Meter
Pattern observed: Voltage is constant in parallel circuits
4.3 1b – 3a 3(1+2+3)
Parallel Circuit – Obtaining Amperage Data
3Bulb - 3b
Bulb - 2bBulb - 1bMaster - 1b
Parallel Circuit - Data
5
Circuit Simulator
0.60Master – 1a 3(1+2+3)
0.21Bulb – 2b 1(2)
0.20Bulb – 3b 1(3)
AmperageAmmeter Placement
Pattern observed: Amperage is additive in parallel circuits
0.21Bulb – 1b 1(1)
Series Circuit
3
1. Place Paperclips as Indicated.
2. Attach Lamp Units.
3. Attach Power Supply.
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
Series Circuits - Obtaining Voltage Data
2
1b – 2b
Series Circuit – Voltage Data
4.81b – 3a 3(1+2+3)
3.21b – 2b 2(1+2)
1.61b – 1a 1(1)
VoltagePlacement of Meter
3
Circuit Simulator
Pattern observed: Voltage is additive in Series circuits
Series Circuit – Obtaining Amperage Data
3
Master – 1b
Series Circuit – Amperage Data
.156Master – 1b 3(1+2+3)
.156Bulb – 2b 1(2)
.157Bulb – 3b 1(3)
AmperagePlacement of Meter
4
Circuit Simulator
Pattern observed: Amperage is constant in Series circuits
.156Bulb – 1b 1(1)
Completed Combined Circuit
3
1. Place Paperclips as Indicated.
2. Attach Lamp Units.
3. Attach Power Supply.
++
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
PolaroidPolapulseBattery
Series Circuit
Parallel Circuit
Combined Circuit - Obtaining Voltage Data
3
Master – 3b1a – 1bMaster – 3b2a -2bMaster – 3b3a – 3bMaster – 3b1a – 3aMaster – 3bPower Source
Combined Circuit – Voltage Data
4.9 1b – 3a (2+3)
2.43a – 3b 2(3)
2.42a – 2b 2(2)
4.91a – 1b 1(1)
VoltagePlacement of Meter
5
Combined
Series
Series
Parallel
Circuit
Note that in series circuit the voltage is additive (2.4+2.4 = 4.8) and in parallel circuits it is constant.
Therefore the circuit voltage would be 4.8.
4.9 Power Source (1+2+3) Combined
Combined Circuit - Obtaining Amperage Data
3
1b – 3aMaster – 1b
Combined Circuit – Amperage Data
5
0.44 Master – 1b 3(1+2+3)
0.27Bulb – 1b 1(1)
0.16Bulb – 2a 1(2)
0.16Bulb – 3a 1(3)
AmperagePlacement of Meter
Combined
Parallel
Series
Series
Circuit
Remember in series circuits amperage is constant and in parallel circuits it is additive.
Therefore if we add the amperage for the series circuit to the amperage for the parallel circuit we should get the amperage for the entire circuit. (0.16 + 0.27 = 0.43)
0.161b – 3a 2(2+3) Series
Conductors
Red (2.5% NaCl)
Green ( 0.5% Sugar)
Blue (10.0% NaCl)
Clear (Distilled Water)
1. Place Paperclips as Indicated.
2. Attach Lamp Unit.
3. Insert paperclips into indicated solutions.
4. Attach Power Supply.
1
Fuses
1. Place Paperclips as Indicated.
2. Attach Lamp Unit.
3. Obtain a strand of steel wool and place it as indicated.
4. Attach Power Supply.
1. Place Paperclips as Indicated.
2. Attach Lamp Unit.
3. Insert Diode.
4. Attach Power Supply.
5. Note orientation of diode, end marker, and switch the diode.
Diodes
Resistors in Parallel
1. Place Paperclips as Indicated.
2. Attach Lamp Unit.
3. Insert resistors 1, 2 and 3 as indicated.
4. Attach Power Supply.
We Had A Great Time
Buzzer Door Bellhttp://www.howstuffworks.com/doorbell2.htm
In a buzzer door bell an electromagnet is used to operate a self-interrupting circuit. One end of the electromagnet is connected to one end of the electrical circuit and the other end of the wire connects to a metal contact adjacent to a moving contact arm. When the electromagnet is turned off, the free end of the arm rests against the contact point. This forms a connection between that end of the wire and the electrical circuit allowing the electricity to flow through the electromagnet when the circuit is closed. This causes the electromagnetic field to attract the iron bar, which pulls the contact arm off the stationary metal contact breaking the connection so the electromagnet shuts off. Without a magnetic field pulling it back, the contact arm snaps back into position against the stationary contact reestablishing the connection between the electromagnet and the circuit, and the current can flow through it again. The magnetic field draws the contact arm up, and the process repeats itself as long as you hold down the buzzer button.
Chime Door Bellwww.howstuffworks.com/doorbell3.htm
A chime doorbell uses a electromagnet called a solenoid. A solenoid is just an electromagnet where the coiled wire surrounds a metal piston. The piston contains magnetically conductive metal, so it can be moved backward or forward by the electromagnetic field.
Speaker
A speaker takes the electrical signal and translates it into physical vibrations to create sound waves. Speakers do this by rapidly vibrating a flexible diaphragm or cone. One end of the cone is connected to the voice coil and the other end to the cone. The coil is attached to the basket by the spider which allows it to move freely back and forth. When electricity passes through the coil a magnetic field is produced which interacts with the magnetic field of the magnetic which causes the coil and cone to move producing sound.
Christmas Lights
These small, low-voltage bulbs with normal house current are connect in series. If you multiply 2.5 volts by 48, you get 120 volts, and originally, that's how many bulbs the strands had. A typical strand today adds two more bulbs so that there are 50 lights in the strand -- a nice round number. Adding the two extras dims the set imperceptibly, so it doesn't matter. The lights in a 50-bulb strand are wired like this:
3
Christmas Lights
If you look closely at a bulb, you can see the shunt wire wrapped around the two posts inside the bulb. The shunt wire contains a coating that gives it fairly high resistance until the filament fails. At that point, heat caused by current flowing through the shunt burns off the coating and reduces the shunt's resistance. (A typical bulb has a resistance of 7 to 8 ohms through the filament and 2 to 3 ohms through the shunt once the coating burns off.)
2
Christmas Lights
Although you can buy simple 50-bulb strands like the one shown, it is more common to see 100- or 150-bulb strands. These strands are simply two or three 50-bulb stands in parallel, like the ones pictured. If you remove one of the bulbs, its 50-bulb strand will go out, but the remaining strands will be unaffected. If you look at a strand wired like this, you will see that there is a third wire running along the strand, either from the plug or from the first bulb. This wire provides the parallel connection down the line.
1
Making a Mini Flashlight
If you hook a mini-light bulb up to a normal AA battery, the bulb will light just like a flashlight bulb. It will be dim, however, because the bulb expects 2.5 volts rather than the 1.5 volts the battery is generating. You can put two batteries together to create 3 volts, or you can hook the bulb up to a 9-volt battery as shown below:
Because you are driving the bulb at a significantly higher voltage than it expects, it will burn extremely brightly and will not last very long (perhaps 30 minutes or an hour).
0
Toaster
The basic idea behind any toaster is simple. A toaster uses infrared radiation to heat a piece of bread. When you put your bread in and see the coils glow red, the coils are producing infrared radiation. The radiation gently dries and chars the surface of the bread. The most common way for a toaster to create the infrared radiation is to use nichrome wire wrapped back and forth across a mica sheet.
mica sheet
Nichrome wire is an alloy of nickel and chromium. It has two features that make it a good producer of heat: Nichrome wire has a fairly high electrical resistance compared to something like copper wire, so even a short length of it has enough resistance to get quite hot. The nichrome alloy does not oxidize when heated. Iron wire would rust very quickly at the temperatures seen in a toaster.
nichrome wire
Light Bulb
The base, of a light bulb has two metal contacts, which connect to an electrical circuit. The metal contacts are attached to two stiff wires, which are attached to a thin metal filament. The filament sits in the middle of the bulb, held up by a glass mount. The wires and the filament are housed in a glass bulb, which is filled with an inert gas, such as argon. When electric current flows from one contact to the other, through the wires and the filament the electrons zip through the filament and bump into the atoms that make up the filament. The energy of each impact vibrates an atom -- in other words, the current heats the atoms up. Electrons in the vibrating atoms may be boosted temporarily to a higher energy level. When they fall back to their normal levels, the electrons release the extra energy in the form of photons or light.
Hair Dryer
A hair dryer needs only two parts to dry your hair: a simple motor-driven fan a heating coil Hair dryers use the motor-driven fan and the heating coil to transform electric energy into convective heat. When you plug in the hair dryer and turn the switch to "on," current flows through the hair dryer. The circuit first supplies power to the bare, coiled wire of the heating element, which becomes hot. The current then makes the small electric motor spin, which turns the fan. The airflow generated by the fan is directed down the barrel of the hairdryer, over and through the heating element. As the air flows over and through the heated coil, heat rising from the coil warms the air by forced convection. The hot air streams out the end of the barrel.
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