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I. Static Electricity II. Current Electricity III. Applications
Electricity I. Static Electricity A. Teaching Static Electricity - Naive IdeasTeaching Static Electricity B. Wonderment of Producing Static Charge 1. Rubbing a. The Fluttering Butterfly....................... 5The Fluttering Butterfly b. The Static Mystery......................... 6The Static Mystery 2. Contact a. Fickle Friends.............................. 7Fickle Friends b. The Repulsive Ball......................... 8The Repulsive Ball 3. Induction a. Dancing Spheres in Captivity.................. 9Dancing Spheres in Captivity b. The Attractive Yard Stick, Broom, and 2 X 4’s.... 10The Attractive Yard Stick, Broom, and 2 X 4’s
Electricity I. Static Electricity C. Explanations - Developing A Model 1. How Do Materials Become Charged?.................... 11How Do Materials Become Charged? 2. Using The Model To Illustrate the Static Charge?......... 12Using The Model To Illustrate the Static Charge? 3. Developing the Laws of Static Electricity a. Golf Tubs and Test Tubes........................... 13Golf Tubs and Test Tubes b. Sticky Tape Static Charges.......................... 14Sticky Tape Static Charges 4. The Electrostatic Series................................ 15The Electrostatic Series a. Where Should We Put Scotch Tape In The Series?........ 16Where Should We Put Scotch Tape In The Series? b. Attractive Stuff.................................. 17Attractive Stuff D. Applying the "Model" For Static Electricity 1. The Moving Soda Can, Ping Pong Ball, or Loony Loop...... 18The Moving Soda Can, Ping Pong Ball, or Loony Loop 2. Groovy Record...................................... 19Groovy Record 3. Electrophorus....................................... 20Electrophorus 4. Electrostatic Doorbell................................ 21Electrostatic Doorbell 5. The Van De Graff GeneratorThe Van De Graff Generator 6. Static Charges Can Kill YouStatic Charges Can Kill You
Electricity II. Flowing or Current Electricity A. Teaching Current Electricity - Naive Ideas............. 22Teaching Current Electricity - Naive Ideas 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 BellBuzzer Door Bell B. Chime Door BellChime Door Bell C. SpeakerSpeaker D. Christmas LightsChristmas Lights E. ToasterToaster F. Light BulbLight Bulb G. Hair DryerHair Dryer
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 C onceptual C hange M odel. 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
Induction - The Attractive Yard Stick, and 2 X 4
Models - How Materials Become Charged OR Learning to Classify based upon Physical Properties RubbingContactInduction 3
Models - How Materials Become Charged Rubbing 2 2 After Rubbing one Material has more and the other has fewer electrons.
Contact 1 Models - How Materials Become Charged 2 After Touching one Material has more and the other has fewer electrons.
Induction 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 become Positively Charged Hard Rubber Comb Vinyl (PVC) - Golf Tube Rubber Balloon Plastic Polyethylene Reynolds or Saran Wrap Styrene Amber Lucite Wood Steel Cotton Paper Silk Cat’s Fur Wool Nylon Human hair Glass Rabbit’s Fur
Electrostatic Series Where Should We Put Scotch Tape In The Series? Substance Does the Scotch Tape Attract or Repel? Charge On: TapeSubstance Transparency Comb Rubber Balloon Plastic Wood Cotton Paper Silk Wool Nylon Glass
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 Electricity Electrophorus \i-lek-'traf- -r s\ 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 Insulated Charged Static Electric Doorbell Transparency
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
Direct and Alternating Current 3 0 No Current Direct Current Alternating Current - Blinking Alternating Current – Solid light
Example Prices for Circuit Boards AP6302Simple 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 AP6302Simple 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 Polaroid Polapulse Battery Polaroid Polapulse Battery Polaroid Polapulse Battery Polaroid Polapulse Battery 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 Polaroid Polapulse Battery Polaroid Polapulse Battery Polaroid Polapulse Battery Polaroid Polapulse Battery
Building the Simple Circuit Board – The Simple Circuit Board P arallel C ircuit S eries C ircuit C ombined C ircuit
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
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 Polaroid Polapulse Battery Polaroid Polapulse Battery Polaroid Polapulse Battery Polaroid Polapulse Battery
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 6.24150948×10 18 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 4.3 Master - 1a 3(1+2+3) 4.3 1b – 2b 2(1+2) 4.3 1b – 1a 1 (1) VoltagePlacement of Meter Pattern observed: Voltage is constant in parallel circuits 4.3 1b – 3a 3(1+2+3)
Combined Circuit – Voltage Data 4.9 1b – 3a ( 2+3 ) 2.4 3a – 3b 2(3) 2.4 2a – 2b 2(2) 4.9 1a – 1b 1(1) VoltagePlacement of Meter 5 Combined 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 – Amperage Data 5 0.44 Master – 1b 3(1+2+3) 0.27 Bulb – 1b 1(1) 0.16 Bulb – 2a 1(2) 0.16 Bulb – 3a 1(3) AmperagePlacement of Meter Combined Parallel 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) 0.16 1b – 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.
Resistors In Series 1. Place Paperclips as Indicated. 2. Attach Lamp Unit. 3. Insert resistors 1, 2 and 3 as indicated. 4. Attach Power Supply.
Buzzer Door Bell http://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 Bell www.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.bread 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.