Electromagnetic Investigations - Day 1

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Objective

Students will engage in a variety of explorations of electromagnetic phenomenon.

Big Idea

It's important to balance theory with observations and to provide evidence for any claim. Students will apply this thinking to four big ideas in electromagnetics.

Overview

Today, we return from a week-long break. We are also transitioning from "seat work" (creating journals) to "lab work" (an investigation of electromagnetic phenomenon). My goal for the day, and for the week, is to set up four stations of electromagnetic phenomenon for students to explore. Students will rotate through each station, looking to collect evidence that supports each of the four ideas. In this unit on "Electromagnetics," students now have the proper background knowledge to explore the wave-particle and induction aspects of electromagnetic radiation. 

Each day, I want to begin with some related content instruction and I want to end with some kind of reflection on progress at the stations. With an 80-minute block, that's not only possible but necessary. The learning targets are HS-PS4-3 and HS-PS4-5 along with NGSS Science and Engineering Practices of planning and carrying out an investigation (#3), analyzing and interpreting data (#4), and engaging in argument from evidence (#7). 

 

Cell Phone Safety Revisited

20 minutes

After returning from break, we need to revisit our discussion of cell phones as possible health hazards. I review the status of the conversation and the summarize reasons for the complexity of the issue with a set of ideas about cell phones on the board. I also prompt students for the arguments they've read about or heard about, whether in support or not of the idea that cell phones are hazardous. Students raise their hands and volunteer the variety of arguments they've heard. As they are nominated, I identify them as being either "skeptical" or "credulous" arguments. Skeptical arguments include the non-ionizing nature of radio waves and the lack of a dramatic increase in brain cancers since the widespread adoption of cell phones. Credulous arguments include the alleged long-term, low-level effects of cell-phone radiation and the caution that we once thought other products (tobacco, asbestos, etc.) were safe and yet those products were eventually shown to be dangerous.

I lead the group through a short conversation about the nature of these kinds of debates. While there are, indeed, two sides to anything, it does not necessarily follow that each side has equally-compelling evidence. In matters like this, it's important to be able to assess the quality of the evidence.

I then ask students to keep in mind the four complicating factors listed on the board (the physics, chemistry, biology, and methodology issues) while they watch an 8-minute video that takes a scientific approach to determining the answer to this question. One benefit of this video is that, at one point in the clip, a person asks, "So, how are we supposed to decide?" Given where we are as a class, that question resonates!

The video caps today's conversation about health risks. In the next section, we turn our attention to the collection of evidence supporting four major aspects of electromagnetics.

Introduction to Four Big Ideas Investigation of Electromagnetics

10 minutes

We switch gears now as I introduce our next set of investigations. I wish to combine a variety of electromagnetic phenomenon ("Four Big Ideas") into one exploration tied by a common theme ("One Big Question"). The Big Ideas are to be explored, one at each of four stations. Two are related to the induction principles (magnetic fields inducing current and vice versa) and two are related to the wave-particle duality of electromagnetic waves. The One Big question is:

"How does your data support the fact that _____________?" where the blank is to be filled in by each of the Big Ideas.

The learning targets are HS-PS4-3 and HS-PS4-5 along with NGSS Science and Engineering Practices of planning and carrying out an investigation (#3), analyzing and interpreting data (#4), and engaging in argument from evidence (#7). 

I hand out the assignment packet which provides drawings and some details about these investigations. I share some quick thoughts about each station, then describe the Big Question and set expectations about what student work should look like. I keep the emphasis on the Big Question - students begin the work at each station by reading over the details provided in the packet.

I reassure students about two things: a) we will take multiple class periods to do this work and b) I will not assign a due date until we let the activity develop a bit. I don't want students rushing through stations to meet a deadline that is poorly chosen. Without the pressure of a deadline, however, I need other ways of ensuring that students are progressing each day. To that end, I introduce two ideas. First, at the end of each day I want to see contributions to an ongoing reflection document, to be added to by each team. Second, half of the assessment of this assignment begins right away - there are grades to be assigned for Self-Direction and Collaboration, two of our school's Learning Expectations. 

I have enough materials for each Big Idea to be explored by two teams simultaneously. Knowing this, it is beneficial to have students work in small (no larger than three people) groups. It is also easy to have student-teams choose a station to start from, without fear of contention for materials.

Electromagnetics Investigation Time

45 minutes

Students quickly gather materials and begin their explorations. I circulate to address concerns and help students get started. 

Here students begin to explore the photoelectric effect. The box in the foreground is a variable AC power source which allows the light bulb to be set to a range of intensities. These students are trying to see a change in voltage across a 100-ohm resistor which is set across the terminals of the photocell.

Here, two groups working on wind turbines (where a changing magnetic field will induce a current to flow) share some thoughts and resources before separating into their respective explorations.

The group in the foreground begins its work with a solenoid, a device which enhances the measurement of a magnetic field induced by flowing charges.

Here. the same group shows its enthusiasm for getting the equipment to work!

This group is intently decoding the diagram in the handout and attempting to create and interference pattern that is the result of the famous double-slit experiment.

As part of that exercise, this student tries, in vain, to use her phone to measure the distance between the two slits. 

Teams continue to work and explore a single station until the last few minutes of class. At that time, I ask for teams to clean up and contribute to a document of "awesome insights" for the day.

Preliminary Data from Electromagnetics Investigations

5 minutes

With about five minutes left in class, I ask each team to clean up and also send a student to the board to add in one "awesome insight" into this first day of exploration. The results are varied but informative. Though this is not an assessment, students are happy to contribute and they get a kick out of seeing their learning documented and becoming public. Also, the act of deciding on which content to share is a minor form of meta-cognition and self-assessment. Because it happens at the very end of the lesson, this reflection provides a way for students to boil down the day into a single statement of learning.