Download Electromagnets Goal: To understand that electricity can form a

Electromagnets
Goal: To understand that electricity can form a magnetic field by using an electromagnet. Materials: Iron or steel bolt in differing diameters, insulated electrical wire, D cell batteries, battery holders with alligator clips, paper clips and other magnetic objects, wire cutters/ strippers, pieces of stainless steel, compass, magnetic film viewer, ammeter.
Background: Magnetic fields act in much the same way as electrical fields. Electricity relies on the imbalance of charges to repel and attract each other. Magnets attract and repel for the same reasons as charges. Throughout time it was suspected that electricity and magnetism go hand in hand. This connection was demonstrated by Hans Christian Orsted in 1820, completely by accident. Orsted noticed that a compass needle is deflected when brought into the vicinity of a current carrying wire. Thus, currents create magnetic fields. At the same time, when an electrical current is passed through a coil of wire a magnetic field is created. So put simply, electricity generates magnetism and magnetism generates electricity. Electromagnets are magnets created by electrical current passing through a coiled wire. It is considered a “temporary” magnet because it can be switched off. Joseph Henry (1820s) perfected the electromagnet. He understood that bare (iron wire) would need spaces in between coils, but insulated wire could have more coils, making the electromagnet stronger. This also allowed him to use a smaller battery.
Electromagnets allowed humans to harness electricity so it could be used (unlike static electricity in lightning). We use electromagnets all the time and probably don’t even know it. Common electromagnets can be found in:
- generators
- electric guitar
- motors
- loudspeaker
- tvs
- vacuum cleaner
- telephone
- dishwasher
- refrigerator
- VCR
- hair dryer
Any time you turn on your TV it is electromagnets that spread out the electrons into lines that make the picture we see. It is electromagnets that operate door chimes, power door locks in our cars and the starters in our car. Electromagnets are used in places like junkyards to lift large pieces of metal and trains rely on them to switch tracks back and forth.
How an Electromagnet works: When Ben Franklin experimented with electricity, he realized that electricity was something that flowed;; it was current, like water running in a pipe. In fact, Ben referred to it as “liquid electricity.” When a battery is connected to a wire to complete a circuit, electricity flows through the wire from one terminal of the battery to the other. This flow of electricity creates a magnetic field around the wire. Coiling the wire concentrates the magnetic field and makes it stronger. The more coils an electromagnet has, the stronger it will be. Likewise, the stronger the battery used, the stronger the electromagnet will be. The most powerful electromagnets are created by using insulated wire tightly coiled around iron. However, they will also work with just a coiled wire. Each coil acts as a tiny little magnet.
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It is important to note that the electromagnet is a temporary magnet because it is no longer magnetized once the electricity is removed. However, sometimes the iron or steel core will retain residual magnetism, which may be difficult to understand. There are some naturally occurring magnets;; for example in ancient Greece and China people noticed lodestone (a mineral) attracted pieces of iron. But most permanent magnets are actually magnetized by being subjected to pressure, heat or electricity. All magnets have two poles, which are places where the magnetic force is strongest.  Safety:  The ends of cut wires may be sharp.  Wires may become warm. Batteries should not be left connected for long amounts of time. Point
Magnet in a coil
To show that magnetism has an effect on electricity. Electromagnet
To show that electricity has an effect on magnetism.
Magnetic Poles
What to do
Questions
Move a magnet through a coiled wire that is attached to an ammeter. Use the electromagnet to pick up and drop paperclips. To show that magnets Use a compass to determine the have poles. magnetic poles of a coil of wire. Change the poles by reversing the flow of electricity. Magnetic induction
To create a Make a temporary magnet by rubbing permanent magnet. metal with a permanent magnet. Compare what the permanent magnet can pick up to what the electromagnet and recently magnetized metal can pick up. Making it stronger
To identify variables Experiment with the different “cores” that will increase of the electromagnet. Alter the the electromagnetic number of coils. Alter the spacing of strength. coils. Test different diameters of wire. What happens when we put the compass near the coil? What about the other side of the coil? What would happen if we tried to flip the battery around?
Where do magnets come from? What ways can you think of to make magnets?
How can you make the magnet stronger?
Resources:
http://science.howstuffworks.com/magnet1.htm
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Magnets and Motors Teacher’s Guide Science and Technology for Children (National Science Resources Center) Smithsonian Institute
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