• Gather materials and make copies of the Building an Electromagnet Worksheet.
• Set up enough Electromagnetic Field Stations to accommodate teams of two students each.
• As an alternative, conduct both parts of the activity as teacher-led class demonstrations.

Figure 2. Set-up for an Electromagnetic Field Station. click for copyright

• Prepare for Electromagnetic Field Stations: Wrap wire around a cardboard toilet paper tube 12-15 times to make a wire loop. Leave two long tails of wire hanging from the coil. Poke four holes in the cardboard. Weave the wire ends through the cardboard holes so that the card board tube and coil are attached to the cardboard (see Figure 2). Use clothes pins, clamps or tape to secure the cardboard to a table or desk. Using masking tape or rubber band, connect one end of the coil wire to any battery, leaving the other end of the wire not connected to the battery. Place some pins, paperclips or tacks at the station. Also, place any other available extra batteries (6V, 12V, etc.) and two, small orienteering compasses at this station.
• Prepare for Building an Electromagnet: For this portion of the activity, either set up the materials at a station, or give them to pairs of students to work on at their desks.
• Keep aside a few extra batteries for students to test their own electromagnets. These might include the 9-V batteries. You can make a 3-V battery setup by connecting 2 D-cells in series or a 4.5-V battery setup by connecting 3 D-cells in series.
• Cut one 2 feet (.6 m) piece of wire for each team. Using wire strippers, remove about ½ inch (1.3 cm) of insulation from both ends of each piece of wire.

1. Divide the class into pairs of students. Hand out one Building an Electromagnet Worksheet per team.
2. Working from the pre-activity set-up (see Figure 2), in which one end of the coiled wire is attached to one end of the battery, have students connect the other end of the wire to the other end of the battery using tape or rubber band.
3. To locate the magnetic field of the electromagnet, direct students to move the compass in a circle around the electromagnet, paying attention to the direction that the compass points (see Figure 3). Direct students to draw the battery, coil and magnetic field on their worksheets. Use arrows to show the magnetic field. Label the positive and negative ends of the battery and the poles of the magnetic field. What happens if you dangle a paperclip from another paperclip near the coil (see Figure 3)? (Answer: The dangling paperclip moves, changes direction and/or wobbles.)

Figure 3. Experimenting with the magnetic field of the electromagnet. click for copyright

4. Next, reverse the connection of the electromagnet by changing both ends of the wire to the opposite ends of the battery. (When the direction of current is reversed in either a coil or electromagnet, the magnetic poles reverse — the north pole becomes the south pole, and the south pole becomes the north pole.) Use the compass to check the direction of the magnetic field. Make a second drawing. Dangle the paperclip near the coil again. What happens? (Answer: Again, the dangling paperclip moves, changes direction and/or wobbles.)
5. Remove at least one end of the wire from the battery to conserve battery power.
6. If time permits, use different batteries and observe any changes. A higher voltage translates to a greater current, and with more current, the electromagnet becomes stronger.

1. Make sure each student pair has the following materials: one nail, 2 feet (.6 m) of insulated wire, one D-cell battery, several paper clips (or tacks or pins) and a rubber band.
2. Wrap the wire around a nail at least 20 times (see Figure 4).
3. Give the students several minutes to see if they can create an electromagnet on their own before giving them the rest of the instructions.
4. To continue making the electromagnet, connect the ends of the coiled wire to each end of the battery using the rubber band to hold the wires in place (see Figure 4).

Figure 4. Set-up to make an electromagnet using a battery, wire and nail. click for copyright

5. Test the strength of the electromagnet by seeing how many paperclips it can pick up.
6. Record the number of paperclips on the worksheet.
7. Disconnect the wire from the battery after testing the electromagnet. Can the electromagnet pick up paperclips when the current is disconnected? (Answer: No.)
8. Test how varying the design of the electromagnet affects its strength. The two variables to modify are the number of coils around the nail and the current in the coiled wire by using a different size or number of batteries. To conserve the battery's power, remember to disconnect the wire from the battery after each test.
9. Complete the worksheet; making a list of ways engineers might be able to use electromagnets.
10. Conclude by holding a class discussion. Compare results among teams. Ask students the post-assessment engineering discussion questions provided in the Assessment section.

Prediction: Ask students to predict what will happen when a wire is wrapped around a nail and electricity is added. Record their predictions on the board.

Brainstorming: In small groups, have students engage in open discussion. Remind them that no idea or suggestion is "silly." All ideas should be respectfully heard. Ask the students:

• What is an electromagnet?

Worksheet: At the beginning of the activity, hand out the Building an Electromagnet Worksheet. Have the students make drawings, record measurements and follow along with the activity on their worksheet. After students finish the worksheet, have them compare answers with a peer or another pair, giving all students time to finish. Review their answers to gauge their mastery of the subject.

Hypothesize: As students make their electromagnet, ask each group what would happen if they changed the size of their battery. How about more coils of wire around the nail? (Answer: There are two ways to make the electromagnet stronger — increasing the amount of electric current going through the wire or increasing the number of wire wraps in the coil of the electromagnet.)

Engineering Discussion Questions: Solicit, integrate and summarize student responses.

• What are ways an engineer might modify an electromagnet to change the strength of its magnetic field. Which modifications might be the easiest or cheapest? (Possible answers: Increasing the number of coils used in the solenoid [electromagnet] is probably the least expensive and easiest way to increase the strength of an electromagnet. Or, an engineer might increase the current in the electromagnet. Or, an engineer might use a metal core that is more easily magnetized.)
• How might engineers use electromagnets in separating recyclable materials? (Answer: Some of the metals in a salvage or recycling pile are attracted to a magnet and can be easily separated. Non-ferrous metals have to go through a two-step process in which a voltage is applied to the metal to temporarily induce a current in it, which temporarily magnetizes the metal so it is attracted to the electromagnet for separation from non-metals.)
• What are some ways that engineers might be able to use electromagnets? (Possible answers: Engineers use electromagnets when they design and build motors. For examples, see the possible answers to the next question.)
• How are electromagnets used in everyday applications? (Possible answers: Motors are in use around us everyday, for example, refrigerator, washing machine, dishwasher, can opener, garbage disposal, sewing machine, computer printer, vacuum cleaner, electric toothbrush, compact disc [CD] player, digital video disc [DVD] player, VCR tape player, computer, electric razor, an electric toy [radio-controlled vehicles, moving dolls], etc.)

Graphing Practice: Present the class with the following problems and ask students to graph their results (or the entire class' results). Discuss which variables made a bigger change in the strength of the electromagnet.

• Make a graph that shows how the electromagnet strength changed as you changed the number of wire coils in your electromagnet.
• Make a graph that shows how the strength of your electromagnet changed as the current changed (as you changed the battery size).