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March 13, 2017

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Contextualizing Sensor Use in a Full Inquiry Framework: Magnetism

Teachers will never be replaced by technology, in part, because science is a highly collaborative endeavor. Even children learning "alone" typically need a facilitator to help them gauge their own discourse as they build and refine their mental models about the world. Recently, my father and physics teacher educator, Carl Wenning, had an opportunity to work with my nephew as he learned about magnetic fields in the context of his homeschooling studies. What resulted was a learning sequence that students, educators, and curious adults might find useful.

 

My father used Physics Toolbox Sensor Suite in the Magnetometer mode to help my nephew quantify his measurements of magnetic field strength, but, as should be the case with technology implementation, it was the learning that was central to this sequence, not the technology. Regardless, the technology is absolutely essential to the full sequence. Before the advent of commercially-available magnetic field sensor probes, it was nearly impossible to widely have students in a class engage in any kind of quantitative inquiry dealing with magnets. (And even then, despite the dozens of sonic rangers and digital force meters I had on hand, I only ever seemed to have a single magnetic field detector...)

 

 

In his guest post below, my father shares a broad context for thinking about how to teach magnetism using levels of inquiry (LoI). Wenning's LoI that my father describes, however, is quite different from Herron's LoI with which most teachers might be familiar. While Herron's traditional and modified versions tend to focus almost exclusively on the "openness" of the inquiry and do not account for the rigor associated with the experimental practices, Wenning's considers both intctual sophistication and locus of control.

Introduction to Magnetism Learning Sequence, by Carl Wenning

 

Wenning and Vieyra (2015), writing in Teaching High School Physics, described a six-level process of inquiry-oriented science instruction (a.k.a. Levels of Inquiry) that can be used to teach science systematically and comprehensively. The authors claim that students who learn under this method of instruction will enhance their understanding, scientific reasoning, and investigation skills.

 

Levels of Inquiry calls for six types of instructional practice, each with its own focus and skill sets. During discovery learning, students develop concepts based on first-hand experiences (a focus on active engagement to construct knowledge). During interactive demonstrations students are engaged in explanation and prediction-making that allows the teacher to elicit, identify, confront, and resolve alternative conceptions (addressing prior knowledge). During the inquiry lesson, students identify scientific principles and/or relationships (cooperative work used to construct more detailed knowledge). During inquiry lab students establish empirical laws based on measurement of variables (collaborative work used to construct more detailed knowledge). During real-world applications, students solve problems related to authentic situations while working individually or in cooperative and collaborative groups using problem-based & project-based approaches. During hypothetical inquiry, students generate explanations for observed phenomena and attempt to test them (experience a more realistic form of science). Ideally, each level will be implemented to the fullest extent and in sequence, but this is not necessarily possible during the study of every science topic.

 

A learning sequence based upon Levels of Inquiry is given below. This learning sequence was designed to introduce students to the phenomenon of magnetism.

 

Discovery Learning

  • Students experience the pushes and pulls of magnets, and note that ends are not alike when comparing two bar magnets.

  • A compass is identified as a magnet, and demonstrated. The “north seeking” end of the needle is defined as North and the opposite end of the needle is defined as South.

  • Students use magnets to “disturb” compasses. They notice that both attraction and repulsion are evident.

  • Students identify poles of bar magnets using compasses, and label N+S as appropriate.

  • A needle is swept with magnet and set upon water and held in place by surface tension (or a small floating piece of paper) showing its ability to orient north-south.

  • Students identify the Earth itself as a source of magnetism.

 

Note from Rebecca: Physics Toolbox Sensor Suite does have compass capabilities and uses the magnetic field detector - not GPS, as some mobile compasses do - and is therefore responsive to actual changes in magnetic field direction. However, there is likely pedagogical merit to using physical compasses when first introducing students to magnetism. Physical compasses allow early students to recognize that compasses are, in effect, small magnets themselves that can spin freely. Digital compasses should only be introduced once they understand that they mimic physical compasses through more complex means.

 

Interactive Demonstration

  • Teacher demonstrates that not all things are attracted by a magnet by using a horseshoe magnet to pick up an empty tin can (zinc-lined steel can) and an empty aluminum soda can.

  • Students test a variety of objects (such as coins, rubber bands, blocks of wood, paper clips, pencils, nails, screws, aluminum cans, etc.) to find things that have magnetic susceptibility.

  • Students are introduced to permanent magnets versus induced magnetism using chains of paper clips held together by a large magnet.

  • Students “measure” the strength of various magnets by daisy chaining hanging ball bearings (all the same size) or paperclips. Teacher uses a Socratic dialogue to help students understand that the greater the number of identical objects suspended, the stronger the magnet.

 

Inquiry Lesson

  • Students observe as the teacher uses a compass to begin to trace out the magnetic field around a bar magnet. (A transparent compass moved around a bar magnet on an overhead works beautifully.)

  • Students using small compasses and a bar magnet, chart the field around the bar magnet. They draw arrows from south to north in the locations where the compasses indicate such directions.

  • Teacher demonstrates the presence of the magnetic field using a bar magnet and iron filings. A piece of paper (or Plexiglas) is used to keep the magnet from the filings. (Note that filings a small, somewhat linear grains of iron that properly line up just as a compass does with the magnetic field of the Earth.)  

  • Student complete a PhET computer-based simulation Magnet and Compass simulation activity to visualize magnetic fields around a bar magnet.

 

Inquiry Lab

  • Guiding question for inquiry lab: Does the strength of a magnetic field change with distance from a magnetic pole? If so, how? Design and conduct an experiment to find out. Make a graph of your experimental results. Use the magnetometer tool in the Physics Toolbox app to find out.

  • Students measure the strength of a magnetic field as a function of distance from a pole, and makes graph. (Must subtract out magnetism of the Earth.)

Note from Rebecca: Physics Toolbox Sensor Suite in Magnetometer mode can display either the digital "overall" value or the graphical output by showing the x, y, and z components, and or total value. The environmental total magnetic field can be subtracted from any measurements when a pole is brought near. We are currently looking to provide a (1) calibration tool to automatically allow users to remove background magnetic field (so long as the device is not moved from its location after calibration), and a (2) manual data entry tool for creating graphs of data like magnetic field strength versus distance from source (measured manually).

 

Real-world Applications

  • Teacher asks, “Where do you see magnets used in daily life?” Students provide examples: power locks, door bells, door latches, magnetic knife rack, computer locks, speaker magnets, motors, refrigerator magnets, toys, compasses, iPod cover clasp, refrigerator doors, can opener, toaster, using magnets as sorters (separating a mix of magnetically susceptible and non-susceptible items).

  • Use a 6-volt dry cell battery, a loop of bell wire, and a compass show that current-carrying wires have a magnetic field.

  • Teacher gives students bell wire, a 6-volt dry cell battery, and a large iron nail. Have them design, create, and demonstrate an electromagnet.

  • Teacher provides students with a DC-drive repeating doorbell and have them examine the inner components to explain how it works.

  • Student Investigates a field around a current-carrying loop; reverse direction of flow of DC electricity and see what happens to field.

  • Use PhET Magnet and Compass activity to simulate field formation in a coil of wire due to a current.

 

Hypothetical Inquiry

  • Have student form one or more hypotheses to explain how the magnetic field in a magnet arises in a magnet (refer students back to current-carrying loop if necessary; current loops of electrons in motion generate magnetic fields). Test hypotheses by appropriate experiment. For instance, if the student suggests that iron atoms are aligned so that all their electrons move one way around their nuclei, heating or pounding on a magnetized nail should disturb this arrangement. Note what happens to the magnetic field after the alignment has been disturbed (the magnetic field disappears).

  • Students are asked the question, “Is there any such thing as a magnetic monopole?” Students are confronted with a refrigerator magnet and asked to explain why one side is “magnetic” while the other side is not. 

    We hope that you find this sequence useful! 

     

     

     

     

     

     

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