MRI Safety Grand Challenge for AP Physics

The design uses a contextually based "Challenge" followed by a sequence of instruction in which students first offer initial predictions ("Generate Ideas") and then gather information from multiple sources ("Multiple Perspectives"). This is followed by "Research and Revise" as students integrate and extend their knowledge through a variety of learning activities. The cycle concludes with formative ("Test Your Mettle") and summative ("Go Public") assessments that lead the student towards answering the Challenge question. See the unit overview below for the progression of the legacy cycle through the unit. Research and ideas behind this way of learning may be found in How People Learn, (Bransford, Brown & Cocking, National Academy Press, 2000); see the entire text at https://www.nap.edu/read/9853/chapter/1.

The Legacy Cycle has similarities to the engineering design process; they both involve identifying a need existing in society, applying science and math to develop solutions and using the research conclusions to design a clear conceived solution to the challenge. Though the engineering design process and the legacy cycle depend on a correct and accurate solution, each focuses particularly on how the solution is devised and presented. An overview of the engineering design process can be found on the web at https://en.wikipedia.org/wiki/Engineering_design_process.

In Lesson 1, students are presented with the following Grand Challenge: A nearby hospital has just installed a magnetic resonance imaging facility that has the capacity to make 3D images of the brain and other body parts by exposing patients to a strong magnetic field. The hospital wishes for its entire staff to have a clear understanding of the risks involved in working near a strong magnetic field and a basic understanding of why those risks occur. Your task is to develop a presentation or pamphlet explaining the risks, the physics behind those risks, and the safety precautions to be taken by all staff members.

Students begin by Generating Ideas in a journal, answering questions such as, "What risk factors could a strong magnetic field pose to medical personnel?" Then students consider the perspective of an MRI researcher as part of the Multiple Perspectives step of the legacy cycle. Students begin the Research and Revise phase with an activity at the end of the lesson to visualize magnetic field lines.

In Lesson 2, students enter the Research and Revise step focusing on how a magnetic field affects charged particles with a deflection of an electron beam demonstration. With teacher instruction, students review vector cross products and are introduced to the Lorentz force. Finally, students participate in a magnetic force on a current carrying wire activity. This lesson concludes with a magnetic fields and forces quiz as part of the Test your Mettle stage of the cycle.

Lesson 3 returns to the Research and Revise step with instruction on torque on a current loop and energy of a current loop in a magnetic field, including example problems.

Lesson 4 proceeds in the Research and Revise phase, introducing the concepts developed from the base knowledge taught in lesson 3. These concepts include the Hall effect, velocity selector and charge to mass ratio.

In Lesson 5, students focus on what produces a magnetic field through the magnetic field around a wire demonstration. This demo is part of teaching students the Biot-Savart law in the Research and Revise phase.

In Lesson 6, students continue learning what produces a magnetic field by studying the field of a solenoid in a slinky activity and relating it to the MRI machine.

In Lesson 7, still Researching and Revising, students being with a demonstration: force between two current loops. The learn Ampere's law and then apply it to calculate the magnetic field around a loop. Then they learn about toroids (a ring form of a solenoid) and their magnetic fields.

Lesson 8 teaches students about induced EMFs with a demonstrations on eddy currents and inducing a jumping ring.

Lesson 9 explores the effects of magnetic fields in matter, including diamagnetism, paramagnetism, ferromagnetism and magnetization. Lesson 9 concludes the Research and Revise phase.

In Lesson 10, students enter the Test Your Mettle phase with a problem set on Ampere's law, Faraday's law, and the sources of magnetic field and induction. Finally, students Go Public with an informative project determining the possible hazards associated with the fields in an MRI scanner.

Magnetic resonance imaging (MRI) technology was developed by biomedical engineers as a noninvasive imaging tool. The technology makes use of concepts within electricity and magnetism whose forces can often be very dangerous but advantageous in their uses. An important task for engineers is ensuring the technology they create is safe and providing instructions to users so that it may be used safely. Engineers must analyze the equipment they design for safety risks and preventing dangers. Throughout the unit, students apply the scientific concepts they learn in electricity and magnetism to the real-world problem of analyzing the risks posed by MRI and developing a means of communicating those to hospital personnel.