CONCEPT: Magnets are fundamental parts of generators and are required to produce current electricity.
CONTENT OBJECTIVE: 4B4.00 To understand the principles of magnetism
INSTRUCTIONAL OBJECTIVES: The learner will:
4.01 distinguish between north pole and south pole of magnets.
4.02 distinguish between repel and attract.
4.03 define magnetic field.
4.04 define electromagnet.
4.05 identify uses of magnets in electricity and communication.
OUTLINE OF CONTENT:
I. North and south magnetic poles
II. Repel and attract
III. Line of force of magnets
IV. Electromagnet
V. Uses of magnets
TN COMPONENT OF SCIENCE: Unifying Concepts of Science
TN GOAL:
To enable students to acquire scientific knowledge by applying concepts, theories, principles and laws from life/environmental, physical, and earth/space science.
TN THEME:
2.4 INTERACTIONS - At all levels of living and non-living systems, matter and energy act and react to determine the nature of our environment.
TN STANDARD(S): The learner will understand that:
2.4b Interactions of matter and energy shape our world.
BENCHMARK: Living things contribute energy to and take energy away from non-living surroundings causing changes in both.
BENCHMARK: The interactions of matter and energy are subject to accepted physical laws.
CLASSROOM CONNECTORS
TIME REQUIRED:
Two instructional periods
MATERIALS:
Bar magnets, horseshoe magnets, compass, cork, needle, plastic container, iron filings, batteries, wire, nail, pencil, tape
SET:
(Have students point "to the North.") Do you know an instrument that can help us? Did you ever use a compass to find your way? (response) If so, you were using a magnet. Does this surprise you? (response) Did you know that magnets are part of many toys? (response) Give examples of objects that have magnets. (Computer disks, cassette tapes, can opener, paper-clip holders, etc.) Today, we are going to learn about magnets, their properties, and how they are used everyday.
INSTRUCTION:
Natural magnets are permanent magnets that never lose their magnetism. This is also true of manufactured magnets, which are created by moving a permanent magnet across steel many times in the same direction or by tapping a piece of steel with a hammer while it is in a coil of wire through which electricity is flowing. Another kind of magnet, which can be strong and is capable of being turned on and off, is called an electromagnet.
A. How is Earth like a magnet? (It has a north and south pole.) If possible, have several compasses available for students to examine. Tell students to look at compasses and notice that the needle moves freely. Explain that the compass needle is magnetic. Let students hold the compass and turn it around. Its needle turns, too. It turns so that it always points north. The needle points to the Earth's Magnetic North Pole.
All magnets attract, or pull toward them, objects made of iron, nickel, or cobalt. Long ago, people found a kind of magnet in nature. These magnets are rocks called lodestones. Lodestones were used as compasses by ancient sailors. Lodestones were called "stones that lead". A compass leads the sailors way.
B. Magnets also repel or push away. Two common shapes of metal magnets are bar magnets and horseshoe magnets.
You will need a bar magnet, magnetized needle, container of water, and a small cork. Scratch a groove in the cork with the needle. Set the needle in the groove. Float the cork on the water. Observe the direction in which the needle points. Bring one end of the magnet near one end of the needle. Ask students what happens. (response) Bring the other end of the magnet to the same end of the needle as before. Ask student what happens. (response)
One pole of a floating magnet will point north. It is called the north-seeking or N-pole. The pole at the opposite end is the south-seeking or S-pole. All magnets have an N-pole and a S-pole.
The N-pole of one magnet attracts the S-pole of another magnet. The N-poles of two magnets repel, or push away from each other. So do the S-poles of two magnets. This is the Law of Magnetic Poles. Like magnetic poles repel. Unlike magnetic poles attract.
C. You know that magnets have force. But, you cannot see that force. You can only see some things that magnets do. You can make a kind of picture of a magnet's force in the space around it. That space is called a magnetic field.
You will need a horseshoe magnet, white cardboard, and iron filings. Place the cardboard over the magnet. Scatter the iron filings over the cardboard. Gently tap the board until the pattern forms. The iron filings make a picture. They show the lines of force in the magnetic field. There are strong lines of force between the pole of the magnets.
D. Electromagnets are temporary magnets that let us turn magnetic field on and off so we can control the magnetic energy. (Make a simple electromagnet by wrapping a wire around a nail and attaching the ends of the wire to a battery to make an electric circuit. As current flows through the coil, a magnetic field is produced and the nail is magnetized.) What are some example of electromagnets? (scrap yard crane, door bell, TV, speakers washers, power plants, etc.)
People use the power of magnets in many ways. Magnetism and electricity are closely related. In an electric generator, an electric current is set up in a coil of wire that moves through a magnetic field. An electric current moving through a wire coil wrapped around an iron core produces magnetism. The close interrelationship between magnetism and electricity has many applications.
Have students experiment with electromagnet (made with a bolt and with a pencil) and paperclips and compass to compare strengths of magnets and effects on the compass.
Why was the bolt stronger? (metal) How could you make the electromagnet stronger? (larger bolt, more wire loops, bigger battery) Which had the biggest effect on the compass? (response)
CLOSURE: Have students divide paper into four sections:
1. Label a magnet
2. Illustrate repel and attract
3. Draw a magnetic field
4. List 10 uses of magnets
Trade with neighbors for discussion.
ENRICHMENT:
1. Write a story describing a day without electricity or products produced by electricity.
2. Make a collage of pictures that show magnets/electromagnets.
3. List A - Z uses of magnets.
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time this file has been accessed since 07/01/97.
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