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Electricity, Magnetism, Circuits, and Motors
Asa Packer Elementary
School, Academic Year 2010-2011
Grade 3 |
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Dr. DeLeo told us that a magnet produces something around it that we can't see. It is called a magnetic field. This is what makes it so hard to push magnets together when held a certain way. Dr. DeLeo showed us how we could see the magnetic field by sprinkling steel needles on a piece of paper just above a magnet.
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We then learned
that electricity is a stream of electrons flowing through
the metal in a wire. The picture on the left
below shows a real electrical wire, like the kind in the walls
of a house. The black part is the plastic insulation,
and the copper colored part, where the insulation was
removed, is the copper metal that carries the electrons
- the electricity. The drawing on the right shows how
the electrons come loose from the atoms that make up the
metal and flow through the wire. A battery creates a force
on the electrons that makes them move, and this is an
electrical current, or electricity.
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Electricity and magnetism are related to each other. As seen on the left, electricity from a battery produces magnetism; this is called an electromagnet. Also, magnetism can be used to make electricity. The picture on the left below shows how we can make electricity by moving a magnet in a coil of wire. The middle picture below shows how this principle is used in one of those flashlights that you shake back and forth. We could see a magnet going back and forth through a coil of wire. In a generator, electricity is produced as a coil of wire is spun around right near a magnet. Dr. DeLeo brought hand crank generators that we could use to make electricity. We could even use one generator to make another one spin, as seen in the picture below on the right. |
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Dr. DeLeo showed us how to make electrical
circuits. The electricity flows from a battery into
a switch. And not just a toy switch, but a real switch
from a real hardware store, just like in our house!
From the switch, the wire went to a light bulb, and
then back to the battery. This is a complete circuit
- starting and ending at the battery. We were given
electrical wiring diagrams to follow. Here we are carefully
examining the wiring diagrams and getting help from our teachers.
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Here are the wiring diagrams we followed. From left to right, we have a “simple” circuit, a “series” circuit, and a “parallel” circuit.
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We began with the simple circuit, and Dr. DeLeo showed us how to follow the wires as we started and ended at the battery. He had us trace the path with our fingers that started at one end of the battery and ended at the other end of the battery. Along the way, we went through the switch and then through the light bulb. Of course we knew that the purpose of the switch was to turn the light on or off, by either letting the electricity go through or stopping it. Dr. DeLeo made us sing "do..dodo..do.dodo..“ as we traced the path. We didn’t really know what the “do..do’s” were about, but it was funny. To see a VIDEO of fingers tracing the path, click the play button on the picture on the left.
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Finally, we began to construct our circuits. We connected wires to other wires using “wire nuts.” First you place the bare ends of two wires next to each other. Then you place the wire nut over both of them, like a hat. Finally, you twist the wire nut to tighten it. Rightsy-tightsy, lefty-loosey. Not only does the wire nut keep the wires from coming apart, it also holds them so tightly together that electricity can flow from one to the other.
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| We used a screw driver to connect wires to the real switches, just like we were grown-ups. |
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And, it worked!! After we wired the simple circuit, we made more complicated circuits using two switches, the series and parallel circuits. Don’t we look happy?
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Dr. DeLeo brought in a make believe wall so we could see what the wires look like in the walls of our house. The wires in the make-believe wall get their electricity from a battery, so it was safe to touch it. BUT!! .. Dr. DeLeo told us that we should never touch the wires in a real wall since that would be very, very dangerous! The wires in the walls of our house use high voltage. The make believe wall had a switch that turned on a light, and a button that made a door bell ring. We had fun making noise with the door bell. We got to ring the door bell every time we got one of our circuits to work. To see a VIDEO of us ringing the bell, click the play button on the picture on the left.
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Below are photos of us with the wall. Even our teachers tried it!
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| Our teachers had us record our observations for the series and parallel circuits in our science notebooks. Then Dr. DeLeo asked us what we discovered from the series and parallel circuits, and he wrote the results on the board. |
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Dr. DeLeo said that series and parallel circuits were like computers since they could make decisions. The series arrangement of switches is called an “AND” gate because the light only lights up if switch 1 AND switch 2 are on. The parallel arrangement of switches is called an “OR” gate because the light lights up if switch 1 OR switch 2 is on. This idea is the basis for computers, digital watches, video games, and many of the electrical devices we use every day.
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Dr. DeLeo also gave us a chance to turn the cranks on hand-held generators to make electricity. We used the electricity to make toy trains run on tracks.
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We learned that electricity and magnetism are related to each other. Magnetism can be used to make electricity, as in a generator. Electricity can be used to make magnetism, as in an electromagnet. An electric motor works by turning a coil of wire into an electromagnet. This electromagnet is pushed by regular (“permanent”) magnets, and that’s what makes the motor turn.
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Dr. DeLeo prepared a coil of wire for each of us to use in building an electric motor. In addition to the coil of wire, we each got a pair of specially bent paperclips (to support the coil of wire and bring electricity to it), a rubber band to hold the paperclips to the battery, and two magnets. We didn’t know it at the time, but Dr. DeLeo’s cat helped with the coils of wire!
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After listening closely to Dr. DeLeo’s instructions, we put together the parts to make an electric motor that worked! And, we got to keep them and take them home. Below are some photos of us with our electric motors. Click the play button on the photo on the left to see a VIDEO.
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Oh, and one last thing. We got to see something very surprising when those new types of (LED) Christmas lights are spun around. You can see from the pictures below that the lights are actually blinking on and off!
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| This is because the electricity that comes out of outlets is "Alternating Current" (called "AC"), meaning it flows back and forth. And since electricity can flow through a diode (the "D" in "LED" - light emitting diode) only in one direction, the light is on half of the time and off the other half - on and off 60 times every second! |
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We were also given a magnetic field viewer that lets us see the magnetic force around a magnet. You can even see the magnetic field of a magnet through your shirt! They are so cool! |
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I hope you have enjoyed this web presentation as much as we enjoyed sharing the actual learning experience with your son or daughter. Although we have endeavored to exclude photographs where permission has been denied, it is possible for errors to occur. If you would like us to remove a photograph of your son or daughter for any reason, please send me an e-mail message at lgd0@lehigh.edu or call me at 610-758-3413, and we will remove it promptly. Please note that we will never associate a child's full or last name with a photograph except in circumstances where special permission was explicitly provided. Thank you. Gary DeLeo. |
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