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Electricity, Magnetism, Circuits, and Motors
Asa Packer Elementary
School, Spring 2009
Grade 3 |
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In this program, we learned
that electricity is a stream of electrons flowing through
the metal in a wire. In most electrical wires, the metal
is copper, and it is covered by an insulating plastic.
Electrons are a part of the atoms that make up the metal.
When the atoms come together to form a metal, the electrons
come loose and move freely. A battery creates a force
on the electrons that makes them move, and this is an
electrical current, or electricity.
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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.
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Electricity can be produced in a number of different ways. One way is by rubbing, like when we rub our feet on a carpet in the winter and give our mom or dad a shock when we touch them. Dr. DeLeo demonstrated a machine that makes electricity in this way. Instead of rubbing feet, it spins a belt very fast. It is called a Van de Graaff generator, and it can make a lot of electricity. In fact, the electricity jumped like a bolt of lightning from the Van de Graaff to another metal sphere nearby! We guessed that this was not a very practical way to make electricity for our homes, so Dr. DeLeo described another way that involved using magnetism.
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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 learned that electricity and magnetism are related to each other. Magnetism can be used to make electricity, as in a generator. Here, 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 to power electric trains. We could even use one generator to make another one spin!
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Just like magnetism can be used to produce electricity, electricity can also be used to produce 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. We got to play with some of the world's simplest electric motors.
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We learned 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, and they are shown below. 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.
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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 electric can flow from one to the other. 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.
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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 are 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 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.
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If you would like to see a video of us scientists at work, then click the play button on the picture on the right.
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Dr. DeLeo gave each of us a little card called a magnetic field viewer. When we place a magnet behind it, we can see the magnetic field. Electricity and magnetism is fun!!
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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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