Hands-on Activity Building an Electromagnet

Learning Objectives

After this activity, students should be able to:

• Describe how the magnetic field of an electric current can be used to create a magnetic field similar to that of a permanent magnet.
• Build an electromagnet.
• Identify the properties of an electromagnet that affect its strength.
• Explain what engineers would have to do to build an electromagnet for use to separate metal for recycling.

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

State Standards

Materials List

Each group needs:

• 1 6-V Zn-C battery (US$1.30)
• 1 compass (diameter 16 mm; US$1.00)
• 1 75-cm length wire
• 1 6.2 V, 0.5 A incandescent light bulb (US$1.30)
• 1 light bulb receptacle (US$1.98)
• 10 staples
• 1 iron/steel nail or other long cylindrical object
• 1 pencil or other long cylindrical wooden object
• other student requested objects that are available in the classroom

Pre-Req Knowledge

An understanding of the magnetic field produced by an electric current and the general properties of an electric current.

Introduction/Motivation

(Have staples ready) To simulate your mess of a recycling plant, you will have 10 staples that your magnet must pick up to be considered successful (show students the staples). Since we know your magnet requires electricity to control it—turn it on or off—you will also have the same supplies from the previous activity. The magnet you are building is called an electromagnet; it is a magnet made from the magnetic field produced by an electric current. Your job is to find the right design and orientation of the wire so that its magnetic field works just like a regular magnet, but you can turn it on and off, and it must be strong enough to pick up these 10 staples. You're on your own; good luck!

Procedure

Background

An electromagnet takes advantage of the induced magnetic field of an electric current to mimic a permanent magnet with the advantage that it can be shut off. An electromagnet requires a continuous supply of electrical energy in order to maintain a magnetic field, which differs from a permanent magnet that doesn't require power. In an electromagnet, the battery's chemical energy transforms to electrical energy in the wire. Additionally, electromagnetic energy in the nail transforms to heat energy.

Setup

• Have ready the first six materials for each group.
• Have ready the remaining materials in a location from which students may browse and choose.

With the Students

1. Divide the class into groups of four students each.
2. Present the Introduction/Motivation section.
3. Give teams time to build an electromagnet. Provide hints about the basic orientation of the wire, but do not give away the looping technique or importance of an iron core until students have begun experimenting with these ideas themselves.
4. Test the performance of the electromagnets using the 10 staples.
5. Ask students to analyze their results as an engineer would. What worked well in the design? What could be improved? What are some other aspects of the design that would be necessary for use at a recycling plant? (Example ideas: An easy switch, some way to move the magnet around so the steel could be dropped elsewhere, safety systems, a durable surface to attract the scrap steel, etc.)
6. As an engineer would, ask each group to document its design as a product description to be presented to the recycling company.

Vocabulary/Definitions

core: An object around which the loops of an electromagnet are wound.

electromagnet: A magnet made from the magnetic field produced by an electric current.

Assessment

The summative assessment is a quiz conducted either after step 4 or after step 5 and is found in the accompanying lesson.

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under National Science Foundation RET grant nos. 0338092 and 0742871. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.