• On Day 1, observe students’ predictions, drawings, and explanations of magnetic fields around the bar magnets. Assess students’ written explanations of how magnetic compasses work.
• On Day 2, observe students during the lab activity, and assess their understanding of the follow-up questions.
• On Day 3, observe students as they complete the lab, and collect and assess the Electromagnet Experiment worksheet.
• Assess students’ understanding during the review game.

Day 1

Note: If you have enough bar magnets and iron filings, the activity below can be done in small lab groups as an exploratory activity.

On the board, write the words in the box below. Have students do a think-pair-share activity to try to figure out what all of the objects have in common. (All of the items are technologies that rely on magnets to work. They also all use electricity.)

Tell students the objectives for this lesson (the first three from the list at the beginning of this lesson). Explain that magnets are objects that produce magnetic fields and attract metals such as iron, nickel, and cobalt. The magnetic field’s lines of force leave the magnet from its north pole and enter its south pole. “Permanent magnets” create their own magnetic field all the time. “Temporary magnets” produce magnetic fields while they are in the presence of a magnetic field and for a short while after leaving the field.

Tell students that refrigerator magnets and bar magnets (show them one) are permanent magnets that are made out of iron oxide mixed with ceramics. Other magnets can be made from alloys, or combinations of metals, such as aluminum, iron, and nickel.

Iron filings (right) align along the magnetic field lines of cylindrical neodymium magnet.

Source: http://static.howstuffworks.com/gif/magnet-3.jpg

By placing two bar magnets on the overhead projector, show students that like poles repel each other and opposites attract. Be sure to label the poles to promote understanding.

Give students the Magnetic Fields worksheet (S-6-6-1_Magnetic Fields and KEY.docx). Show students a bar magnet. Explain that magnets have north and south poles and explain what a magnetic field is. On the board, draw the bar magnet, label the north and south poles, and draw magnetic field lines (see diagram below). Have students diagram the magnetic fields on the bar magnet at the top of the worksheet.

Turn on the overhead projector and lay the magnet on it. Place the piece of Plexiglas over the bar magnet and use a spoon to sprinkle iron filings over it. (Note: Model lab safety by wearing goggles.) Show students how the alignment of the iron filings matches the diagram of magnetic fields on the board. Explain that the magnetic field lines come together where the force is strong and spread out where it is weak.

Have students draw their predictions for the magnetic fields for the examples on the worksheet. In the meantime, clear the iron filings from the Plexiglas. Place two bar magnets on the overhead with the north and south poles facing, as in the first diagram. Place the magnets just far enough apart so that they do not stick together. Place the Plexiglas over the magnets. Have several students share their predictions and then call on one student to spread the iron filings over the magnets, using the spoon and wearing goggles. Have students draw their observations on the worksheet. Repeat for the second example, calling a new volunteer. Have students complete the bonus question independently.

Show the class a compass and ask if any students have used a compass or if they know what a compass is used for. Have students share what they already know about compasses. If you have several compasses, pass them around the class. Demonstrate how to use the compass. Show them the needle and point out that one end is colored to indicate that it is pointing north.

Source: http://outreach.phas.ubc.ca/phys420/p420_01/shaun/shaun/whyit7.jpg

Briefly explain how compasses work. Explain that the Earth has a magnetic field. Draw a diagram similar to the one above, and explain that the magnetic north and south poles are the opposite of the geographic north and sole poles. Have students copy the diagram in their notes.

Show students the “What the Ancients Knew: Chinese Magnetic Compass” video at http://videos.howstuffworks.com/science-channel/29775-what-the-ancients-knew-chinese-magnetic-compass-video.htm. Before showing the video, post these questions to provide focus:

• Why did ancient Chinese people make compasses out of lodestone?

(It is a naturally occurring magnetic material that aligns with the Earth’s magnetic field.)

• What did they use compasses for?

(They used them to find good locations for burials and ceremonies, to plan their cities, and to explore at sea.)

Divide students into small groups for the lab activity, Creating Your Own Homemade Compass (S-6-6-1_Compass Lab.docx). Read through the directions with students and then distribute the materials. Note: Use a straightened paper clip instead of a sharp needle! If each group has a compass, have them compare the “needle” on their homemade compass to verify that is pointing north. If not, visit each group with your compass for comparison.

To close the lesson, have students write a one or two sentence explanation of how magnetic compasses work.

Day 2

To prepare, set up an example of a simple circuit like the one shown below:

Source: www.consumersenergy.com/uploadedFiles/Kids/Conductors%20and%20Insulators.pdf

Have students look at the example circuit and ask, “How does the electrical energy move from the battery to the light bulb?” (The electricity moves through the metal wires.)

Explain the terms conductor and insulator and relate them to the materials in the circuit. Have students suggest how the circuit could be used to test materials to see if they conduct electricity.

Hand out the Electrical Conductors and Insulators lab worksheet (S-6-6-1_Conductors and Insulators and KEY.docx). Have students work in small groups to conduct the lab. Circulate around the room to assist with setting up circuits and answer questions. When they are done with the activity, have students clean up materials and then answer the questions at the bottom of the worksheet. The questions can be assigned for homework if time is limited. Review the answers with the class.

Day 3

Ask students to recall how they magnetized the paper clip when they were making the magnetic compass on Day 1. Tell students that you can also use electricity to build a strong temporary magnet called an electromagnet.

Explain that electromagnets only produce magnetic fields when electricity travels through their wire coils. Tell students that the electromagnet was invented in 1825 by William Sturgeon. He discovered that electricity flowing through a copper wire with a piece of iron in the center of it created a powerful magnet.

Hand out the Electromagnet Experiment worksheet (S-6-6-1_Electromagnet Experiment and KEY.docx). Read through the procedure with students and caution them to disconnect the wire from the battery for a few minutes when the nail becomes warm. Monitor student groups as they complete the lab activity. Have students clean up all lab materials. Optionally, have students graph the results from the data table.

Day 4

Divide students into groups of six for a modified jigsaw activity. Give two students from each group the reading selection on motors, two students the selection on generators, and two students the selection on homemade motors from Generators and Motors (S-6-6-1_Generators and Motors.docx). Assign the “Motor in 10 Minutes” selection to students who are going beyond the standards. As they read, have students highlight the articles and/or take notes. All groups will try to answer the question, “How can moving magnets produce electric forces in a motor/generator?”

Allow time for “expert” students to read and then discuss their reading selection with the home group. Have the experts share what they have learned about how motors and generators work with one another. Monitor groups and ensure that the focus of the discussions is on the relationship between magnets and electricity in motors and generators.

Wrap up the activity by asking the whole class, “How can electric generators be considered the opposite of electromagnets?” (In electric generators, moving magnets produce electrical energy. In electromagnets, moving electric charges produce magnetic forces.)

Concept Review

Play a True–False review game on magnets and electricity. Read each statement below. If it is True, have students stand up. If it is False, they should sit down.

1.   Magnets have north and south poles. (True)

2.   Like poles attract each other and opposite poles repel each other. (False)

3.   Magnetic forces attract only magnetic materials. (True)

4.   Magnetic forces act at a distance. The objects don’t have to touch each other. (True)

5.   While magnetized, temporary magnets act like permanent magnets. (True)

6.   A coil of wire with an electric current flowing through it becomes a permanent magnet. (False – temporary)

7.   Insulators allow electricity to pass through them. (False)

8.   Copper wires are good conductors of electricity. (True)

9.   Electric generators use moving magnets to produce electrical energy. (True)

10. You can tell which way is north because the colored end of the compass needle points to the north. (True)

Extension:

• Students who may need an opportunity for additional learning can be shown models of the handmade compass, circuit, and electromagnet. Guide them through the procedures step-by-step.
• Students who might need more practice can make a Venn diagram comparing magnets and electromagnets to review concepts (S-6-6-1_Venn Diagram.docx).
• For students who may need an opportunity for additional learning, provide a written worksheet of the review-game statements to practice independently as a follow-up to the lesson (S-6-6-1_Concept Review and KEY.docx).
• Students who might be going beyond the standards can read one of the articles below and write a paragraph defending why it is worth developing the world’s most powerful magnet.

• Students who might be going beyond the standards can write a paragraph describing a product that would not operate well if different materials were used in its construction. For example, a light bulb built with a plastic thread for a filament would not operate.
• During the Electromagnet Experiment, challenge students to build a new electromagnet in which they change a different variable, draw it, and record the results.