Hands-on Activity: Slinkies as Solenoids

Contributed by: VU Bioengineering RET Program, School of Engineering, Vanderbilt University

A photograph shows a metal slinky, arched to show its composition.
A metal slinky functions as a solenoid in this activity.
Copyright © 2008 Megan Brock, Free Images, Getty Images http://www.sxc.hu/photo/61986


Students use a classic children's toy, a metal slinky, to mimic and understand the magnetic field generated in MRI machines. The metal slinky mimics the magnetic field of a solenoid, which forms the basis for the magnet in MRI machines. Students run current through the slinky and use computer and calculator software to explore the magnetic field created by the slinky.
This engineering curriculum meets Next Generation Science Standards (NGSS).

Engineering Connection

Solenoids form the basis for the magnet of MRI machines, an imaging tool designed by engineers. Exploring the properties of this solenoid helps students understand the MRI machine. In handout questions 5 and 6, students are asked to apply what they have learned during the experiment to design a safe environment around MRI machines.

Learning Objectives

After this activity, students should be able to:

  • Determine the relationship between magnetic field and the number of turns per meter in a solenoid.
  • Explain how the field varies inside and outside a solenoid.
  • Design an experiment that measures the value of μ0, the permeability constant.

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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.

  • Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as either motions of particles or energy stored in fields. (Grades 9 - 12 ) More Details

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    This Performance Expectation focuses on the following Three Dimensional Learning aspects of NGSS:
    Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
    Develop and use a model based on evidence to illustrate the relationships between systems or between components of a system.

    Alignment agreement:

    Energy is a quantitative property of a system that depends on the motion and interactions of matter and radiation within that system. That there is a single quantity called energy is due to the fact that a system's total energy is conserved, even as, within the system, energy is continually transferred from one object to another and between its various possible forms.

    Alignment agreement:

    At the macroscopic scale, energy manifests itself in multiple ways, such as in motion, sound, light, and thermal energy.

    Alignment agreement:

    These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy can be modeled as a combination of energy associated with the motion of particles and energy associated with the configuration (relative position of the particles). In some cases the relative position energy can be thought of as stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space.

    Alignment agreement:

    Energy cannot be created or destroyed—it only moves between one place and another place, between objects and/or fields, or between systems.

    Alignment agreement:

  • Fit a linear function for a scatter plot that suggests a linear association. (Grades 9 - 12 ) More Details

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  • Interpret the slope (rate of change) and the intercept (constant term) of a linear model in the context of the data. (Grades 9 - 12 ) More Details

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  • Medical technologies include prevention and rehabilitation, vaccines and pharmaceuticals, medical and surgical procedures, genetic engineering, and the systems within which health is protected and maintained. (Grades 9 - 12 ) More Details

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  • Use computers and calculators to access, retrieve, organize, process, maintain, interpret, and evaluate data and information in order to communicate. (Grades 9 - 12 ) More Details

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  • Results of scientific inquiry--new knowledge and methods--emerge from different types of investigations and public communication among scientists. In communicating and defending the results of scientific inquiry, arguments must be logical and demonstrate connections between natural phenomena, investigations, and the historical body of scientific knowledge. In addition, the methods and procedures that scientists used to obtain evidence must be clearly reported to enhance opportunities for further investigation. (Grades 9 - 12 ) More Details

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Materials List

Each group needs:

  • magnetic field sensor
  • Physics with Vernier Lab Book
  • metal slinky
  • switch
  • meter stick
  • DC power supply
  • ammeter
  • connecting wires
  • non-conducting tape, such as masking tape
  • Slinky Lab Handout, one per student

The cost of durable goods needed for this lab—magnetic field sensor, Physics with Vernier Lab Book, DC power supply, ammeter and connecting wires—totals ~$250.

Note: The lab description describes the lab using Vernier magnetic field sensors and equipment, but the lab can be adapted to any sensor and calculator or computer. Vernier sensors can be ordered from www.vernier.com. Other companies include Pasco (www.pasco.com), and Texas Instruments (www.ti.com)


A solenoid is made by taking a tube and wrapping it with many turns of wire. A metal slinky is the same shape and can serve as a solenoid. When a current passes through the wire, a magnetic field is present inside the solenoid. Solenoids are used in electronic circuits or as electromagnets. (source: Vernier)

In this lab, you will explore factors that affect the magnetic field inside the solenoid and study how the field varies in different parts of the solenoid. By inserting a magnetic field sensor between the coils of the slinky, you can measure the magnetic field inside the coil. You will also measure μ0, the permeability constant. The permeability constant is a fundamental constant of physics. (source: Vernier)

An MRI machine uses a large solenoid to create its magnetic field. By exploring the properties of a small solenoid (the slinky), we can predict the properties of the MRI magnet. It is important to note where the solenoid's magnetic field is strongest, and ways of making the magnetic field of a solenoid stronger in order to understand MRI safety.



To explore the properties of a small solenoid, students complete a lab modified from Vernier's "The Magnetic Field in a Slinky" online lab that is available free of charge at https://www.vernier.com/experiments/pwv/26/magnetic_field_in_a_slinky/. The first two "introduction" paragraphs at this website are included in the Introduction/Motivation section because they provide a useful background and introduction for students.

Before the Activity

With the Students

  1. Divide the class into small groups of two or three students each. Distribute materials and the handout.
  2. Direct students to follow the initial setup indicated on the handout, then design an experiment to answer the later questions in the handout. Have students refer to the handout for guidance.
  3. Expect students to be able to design and describe their own procedures.
  4. During the experiment, walk around the student groups and answer questions, as needed.
  5. Conclude by giving students time to individually prepare summary lab reports as directed in the handout.

Worksheets and Attachments


Embedded Assessment: Assign students to create lab reports in which they design experimental procedures to answer a number of questions on the Slinky Lab Handout. These questions also ask students to apply what they have learned about solenoids to creating a safe MRI machine. Review their lab reports to verify their understanding of the concepts.


The Magnetic Field in a Slinky. (Grades 9-12) Physics with Vernier. Vernier Software and Technology. Accessed July 21, 2008. Original URL: https://www.vernier.com/cmat/pwv.html; new URL: https://www.vernier.com/experiments/pwv/26/magnetic_field_in_a_slinky/


Eric Appelt


© 2013 by Regents of the University of Colorado; original © 2006 Vanderbilt University

Supporting Program

VU Bioengineering RET Program, School of Engineering, Vanderbilt University


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.

Last modified: September 5, 2017