Download Electromagnetism Book Notes KEY

Unit 7 Lesson 5
ELECTROMAGNETISM (REGULAR) - KEY
(Pages 454 – 467)
Instructions: Fill in the skeleton notes as you read the pages listed above. Remember to complete any of the
questions in the book as you read.
Page 455
Complete the Engage Your Brain section
Complete the Active Reading section
Page 456
What is electromagnetism?
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Electromagnetism results when electric currents and magnetic fields interact.
The Interaction Between Magnets and Electricity
-
How did Hans Christian Oersted discover that magnetism and electricity were related?
Brought a compass close to a wire that was carrying an electric current and observed that the
compass needle was affected by the wire (it moved away from north)
Magnetism Produced by Electricity
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When a wire is carrying an electric current, a magnetic field is produced around the wire
-
Compasses surrounding a wire that has an electric current running through it show that an electric current
produces a circular magnetic field around the wire (*HINT – Look at the pictures in your book on the left
side of the page)
Page 457
How can you make a magnet using current?
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A weak magnetic field is produced when an electric current runs through a single loop of wire.
Make a magnet with a solenoid
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Define solenoid: A coil wire that carries an electric current and produces a magnetic field
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The more loops in the wire coil, the stronger the magnetic field
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The stronger the electric current, the stronger the magnetic field
Make a magnet with an electromagnet
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To make an electromagnet a solenoid can be wrapped around an iron core.
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Wrapping a wire around an iron core and running a current through the wire causes the iron core to
become magnetized
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An electromagnet is stronger than a solenoid because it combines the magnetic field of the solenoid with
the magnetic field of the magnetized iron core
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The more loops in the wire coil, the stronger the magnetic field of the electromagnet
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The stronger the electric current, the stronger the magnetic field of the electromagnet
Complete the Active Reading Section (#6)
Page 458
What are some uses for electromagnets?
List four examples of how electromagnets are used.
1. Doorbells
2. Lifting Metal Objects
3. Hair Dryer
4. Blenders
5. Atom Smashers
6. Speakers
Complete the Inquiry section (#7)
Page 459
A Look Inside
MRI stands for magnetic resonance imaging. It uses electromagnets and radio waves to help doctors 'see'
inside the body.
Complete the Extend section (#8 & #9)
8. Explain Why are the electromagnets in MRIs kept at very low temperatures?
It takes less energy for the electric current to flow at low temperatures
9. Infer Why are electromagnets, rather than permanent magnets, used in MRIs?
So that the electromagnet can be turned off; electromagnets can be made more powerful than
permanent magnets
Page 460
Electric Motors
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An electric motor changes electrical energy into mechanical energy
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Almost every time a device uses electricity to make something move, there is a motor involved
List two places that electric motors can be found
1. Computer Fan
2. Ferris Wheel
3. Hair Dryer
4. Blender
Page 461
Motors Use Electromagnets
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A simple motor has a coil or loop of wire called an armature mounted between the poles of a magnet
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The armature becomes an electromagnet when current passes through it
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The armature rotates because its poles are pushed and pulled by opposite poles of the magnet
Page 462
Electromagnetic Induction (*Hint – Use the pictures on the right hand side of the page to fill in the blanks)
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A magnetic field can be used to create an electric current in a wire
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An electric current is induced when a magnets moves through a coil of wire
-
To increase the electric current:
o
Move the magnet through the coil at a faster rate
o
Add more loops of wire
Complete the Visualize It section (#13 & #14)
Page 464
Electric Generators
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Most of the electricity you use every day comes from electromagnetic induction
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Electric generators use induction to change mechanical energy into electrical energy
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Electric generators are the opposite of electric motors
Generating Electricity with a Magnetic Field
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In power plants, mechanical energy (from sources like steam, blowing wind, falling water, and ocean
tides) is used to rotate turbines
o
Turbines are machines that have blades that are caused to spin by pressure from water, steam, or
air
-
The turbines turn magnets inside coils of wire, which generates electricity
Page 466 Complete the Visual Summary (#20 – 26)
Page 467 Complete the Lesson Review (#1 – 8)