Magnet Mining

Overview

How was magnetism responsible for the destruction of dozens of ships during World War II? In this lesson, your students will explore the concepts of magnetic fields and forces using the example of World War II magnetic mines. With the help of a magnetometer and Google's Science Journal app, students will investigate what factors affect the strength of a magnetic field. Then they will use their knowledge to try to discover the location of hidden "mines" and investigate how they can cloak a magnetic field to become undetectable by a magnetic trigger mechanism.

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:

• MS-PS2-3. Ask questions about data to determine the factors that affect the strength of electric and magnetic forces.
• MS-PS2-5. Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact.

This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices	Disciplinary Core Ideas	Crosscutting Concepts
Planning and Carrying Out Investigations. Collect data to produce data to serve as the basis for evidence to answer scientific questions or test design solutions under a range of conditions. Conduct an investigation and evaluate the experimental design to produce data to serve as the basis for evidence that can meet the goals of the investigation. Analyzing and Interpreting Data. Analyze and interpret data to provide evidence for phenomena. Constructing Explanations and Designing Solutions. Undertake a design project, engaging in the design cycle, to construct and/or implement a solution that meets specific design criteria and constraints. Engaging in Argument from Evidence. Construct and present oral and written arguments supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon or a solution to a problem.	PS2.B: Types of Interactions. Electric and magnetic (electromagnetic) forces can be attractive or repulsive, and their sizes depend on the magnitudes of the charges, currents, or magnetic strengths involved and on the distances between the interacting objects. Forces that act at a distance (electric, magnetic, and gravitational) can be explained by fields that extend through space and can be mapped by their effect on a test object (a charged object, a magnet, or a ball, respectively).	Cause and Effect. Cause and effect relationships may be used to predict phenomena in natural or designed systems. Systems and System Models. Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy and matter flows within systems. Influence of Science, Engineering, and Technology on Society and the Natural World. The uses of technologies and any limitations on their use are driven by individual or societal needs, desires, and values; by the findings of scientific research; and by differences in such factors as climate, natural resources, and economic conditions.

Materials

Materials per group of 2–3 students:

• Ceramic disc magnets, 18mm diameter (5), available from Amazon.com
• Printout of grid paper template (5-6). Note: You might need to adjust the size of the template based on the boxes you use.
• Construction paper (darker color but not black)
• Duct tape
• Pencil or pen
• Transparent shoe or storage box, available from Amazon.com
• Aluminum foil
• Materials for cloaking activity: your students can get creative here. Some possibilities are aluminum foil, additional magnets, copper wire (non-magnetic), iron wire (magnetic), foam sheets, paper, etc.
• Smartphone with a sensor app such as phyphox, available for free on Google Play for Android devices (version 4.0 or newer) or from the App Store for iOS devices (iOS 9.0 or newer). Note: This lesson works best with an Android phone equipped with a magnetometer. The magnetometer on an iOS device sometimes shows elevated background readings and can shut off when exposed to high magnetic fields.

Materials for teachers:

• Two bar magnets