Hands-on Activity Electricity & Magnetism:
Whose Field Line Is It, Anyway?

Learning Objectives

After this activity, students should be able to;

• Describe current.
• Explain how voltage produces a current.
• Explain how current produces a magnetic field.
• Describe the interconnection of electricity and magnetism.
• Identify how magnetic field lines are generated in relation to a coil of wire that has a current.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

Materials List

Each group needs:

• 1 bar magnet (rectangular)
• 1 sheet of paper
• 1 3/16-in iron nail (3-in long)
• 2 meters of 28 to 32 gauge copper magnet wire (bulkwire.com)
• 100 g of iron filings
• 1 battery (AA, AAA or 9V)
• 1 pair of wire strippers
• Fields Lines Worksheet one per student

Worksheets and Attachments

Introduction/Motivation

You will easily accept that if you push an object, if it is free to do so, it will move. You are able to see how the object moves. However, forces (or pushes and pulls) exist that are not as easily seen. The most pertinent example in our lives is gravity. We know it exists because we do not float away from the Earth, and everything falls down. However, understanding how this force acts on us can be difficult since it is far less visible or tactile than pushing on an object.

Magnets are much the same way. From observation, we know two magnets exert a force on each other. However, we cannot see contact between the magnets when they start pulling on each other. Therefore, we use field lines.

Field lines are a visual representation of force. They show the path an object would be pushed or pulled when acted upon. For a vacuum cleaner, the field lines would be pointing into the bottom where the air is pulled in (see Figure 1). For the Earth's gravity, all the field lines would be pointing towards the center of the Earth. On a magnet, the field lines point from the north pole to the south pole. This is the direction another magnet would be pulled if brought close to it.

For electromagnets, field lines are convenient. When iron shavings are poured around a magnet, they line up with the force field lines around it. This gives us a great visual representation of the invisible force of magnets. At the same time, when iron shavings are sprinkled around an electromagnet, it gives us a great visualization showing the similarities and differences between magnets and electromagnets.

Procedure

Background Information for the Teacher

The relation between magnetism and electricity is one of the key concepts in science. Knowledge of this connection led to the ability to generate electricity for our homes, the operation of moveable parts in almost every electrical device, the ability to communicate wirelessly, the ability to perform noninvasive medical procedures, the ability to see electrical signals become images on our TVs, and so much more.

The key concept that students should take away from the activity is that a magnetic field created by running a current through a wire is the same as a magnetic field created by a magnet. At the same time, students learn that an electromagnet can be turned on and off, unlike a standard magnet. From this concept, students can then understand how so many other devices around them function.

Before the Activity

• Gather materials and make copies of the Field Lines Worksheet.
• If time for the activity is limited, make the electromagnets in advance (steps 7 through 9).
• Divide the class into teams of two to four students each, and lead them through the steps below.

With the Students

1. Place a bar magnet on a flat surface, such as a desktop.
2. Place a piece of paper over the bar magnet so that it is completely covered and near the center of the paper.
3. Sprinkle iron filings onto the paper around the bar magnet. Avoid dropping large clumps in a single spot.
4. Gently shake the paper until field lines are easily seen.
5. On your worksheet, sketch a picture showing how the shavings line up around the magnet.
6. Carefully lift the paper and remove the magnet; then place the paper (with iron filings still on it) back on the flat surface. TIP: Attempt to not let any filings touch the magnet. Once fillings touch the magnet, it can be very difficult to remove them.
7. Wrap the copper wire around the nail, leaving 4 inches of free wire at either end. Try to keep the windings tight and close together.
8. Place one of the copper wires between the blades of the wire strippers. Gently pull the wire out. If done properly, you should see specks of golden brown on the scissors blades. This is the wire coating.
9. Repeat step 8 with the other end of the wire.
10. Place the nail in the center of the iron filings.
11. Gently shake the paper.
12. Sketch the pattern made by the filings at this point.

13. Place either end of the wire on either contact of the battery, and then gently shake the paper (see Figure 2).
14. Sketch the pattern made by the shavings. Note that the magnetic field pattern, that you have just demonstrated through your experiment, is important in designing and creating everyday engineering products such as electric motors and electric generators.
15. Conclude with the post-activity assessment described in the Assessment section, and having students complete the worksheet questions.

Vocabulary/Definitions

current: A flow of electric charge. Current can also be described as the rate of flow of electric charges. In most cases, current is associated with the flow of electrons.

electricity: Any phenomena that can be associated with the presence or flow of electric charges.

electromagnet: A type of magnet in which the magnetic field is produced by the flow of current. A temporary magnet created by running a current through a coil of wire that is wrapped in a loop; usually this loop is wound around a piece of metal such as iron or iron compound.

field lines: Imaginary lines used to show direction of force. While most often used in magnetism, they are also used to illustrate electricity and gravity.

magnetic: Relating to or caused by magnetism; having the properties of a magnet, that is, of attracting iron or steel.

magnetism: The energy and forces associated with magnetically charged particles, such as those found in bar magnets; due to the Earth having a magnetic field that consistently points in the same direction, magnets have for a long time been used in navigation; magnetism is due to the movement of electrically charged particles, such as electrons.

voltage: Common name for electric potential difference. It is the driving force for electric current traveling from a point A to B; expressed in volts.

Assessment

Activity Embedded Assessment

Worksheet: During the experiment, have students draw their observations of field lines on the Field Lines Worksheet, and then answer the worksheet questions. Review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Understanding of Electromagnets: To assess what students have learned, ask them to identify at least one similarity and one difference between a magnet and an electromagnet. (Possible answers: Similarities—they both act on iron, they pull on each other, they both have lines oriented from one end to the other, they both have a north pole and a south pole [or oppositely charged ends]. Differences—electromagnets use electricity while normal magnets do not, normal magnets are permanent while electromagnets can be turned on and off. Possible incorrect answers: One is stronger than the other. This property is based upon how the magnet and electromagnet are shaped, made, and what material they are made of, which can be seen in the associated activity, The Good, the Bad and the Electromagnet.)

Copyright

Contributors

Supporting Program

Acknowledgements

This curriculum was developed by the USF Students, Teachers and Resources in Sciences (STARS) Program under National Science Foundation grant numbers DGE 0139348 and DGE 0638709. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.