Peer Instruction Online Update

I really like Eric Mazur’s Peer Instruction technique. You can read about how I have used it in a face-to-face environment here:

Original Peer Instruction Blog Post

This instructional technique increases student engagement (they ask if they have a question for the day when they come in!), allows them to practice their argumentation skills (Science Practice 6, Argumentation), and can increase understanding of the basic concepts. 

The basic sequence is 

1. Project an interesting multiple choice conceptual (or maybe semi-quantitative) question

2. Students answer individually (no discussion) and anonymously

3. Students view a graph of the class’s responses

4. Students discuss with each other how they responded and why. They try to reach consensus with their discussion partners.

5. Students answer the same question again.

6. The class views the responses and the teacher leads a consensus-building discussion

The way I have used it, Peer Instruction depends on students discussing face-to-face, but how do you do that with a hybrid or online environment?

One short answer is that you can do this with PearDeck.com. This is an add-on to Google Slides. It allows you to add many types of questions to a Google Slide. The students join a Pear Deck session, view the question, and enter their responses. You can then show the graph of student responses from Pear Deck, and go through the sequence above. You need to have made a slide show with the same multiple choice question in it twice. Here is an example of a Pear Deck Slide show for a Paul Hewitt Next-Time Question.

If you don’t want to use Pear Deck, or you want to try and get the effect of Peer Instruction asynchronously, I did read about a way to use Peer Instruction online without live interaction. In The Physics Teacher journal online, I read this article, Peer Tutoring in Web-based Concept Tests. The authors used LON-CAPA to collect student justifications along with their responses. Instead of interacting live, the students can view other’s justifications.

A modification of this involves providing simulated interactions. You would present the multiple choice question, have students answer, then have them view student statements about the question and the choices. Then, after the simulated interaction, they vote again. 

Here is the Paul Hewitt Next-time question that is embedded in the “Original Peer Instruction Blog Post” referenced above:

Below are a few “student” statements I wrote to go with the question, based on my memory of how this discussion typically goes.

“The scale reads zero, because the forces on the string from each side are in opposite directions and cancel out.”

“The scale reads 100 N because the string has to hold up the 100 N weight on each side.”

“I know the objects are at rest, but it seems like each object has an effect on the scale, so I guess 200 N.”

“The scale reads 200 N because the string has to hold up two 100 N objects.

“If the scale read 200 N, wouldn’t that mean that a 100 N weight was flying upwards?”

“The scale can’t read zero because we know if you touch the string there is tension in it, right?”

Please share thoughts on using Peer Instruction in the Virtual/Hybrid Classroom in the comments.

Covid-19 AP Physics Writing “Workshop”

Science teachers want students to think like scientists, write like scientists, and investigate like scientists. Writing has special prominence in AP Physics 1 and 2.

In order to learn to write like a scientist, students have to practice writing, get feedback, respond to the feedback, and revise their writing. Using an LMS and a few simple guiding principles can make that writing-feedback-revising cycle work in the classroom.

The Covid-19 Pandemic has caused a lot of changes in the lives of teenagers and their teachers this spring. School for us closed on March 12, and we went to online instruction through Google Classroom and Zoom meetings. The College Board elected to make all AP Exams online, 45 minute exams. The AP Physics Exams this year consisted of only two free-response questions. The questions could be answered completely by typing. None of the questions required drawings, diagrams, graphing, or derivations. In previous years, all of these tasks were very important parts of the AP exams. I spent a lot of time last year training my students to do them. Now, they were going to write about the tasks, and they were free to use notes, textbooks, or Google to help them answer the questions.

So, I changed the way I wrote my assignments. I turned drawing free-body diagrams into “describe the forces” and “calculate” into “does this equation make sense”? And I changed the way I assessed assignments. I instituted a new grading scheme. I commented on every part of every assignment. Relatively flawless work earned a 100%. Students whose work had major flaws were allowed to revise and resubmit multiple times. If a student didn’t get the work up to my standards, they earned a 60%.

This system worked very well. Rather than checking for right answers, I was looking for correct understanding. Instead of getting a grade, students were getting feedback and felt compelled to respond to the feedback. It sometimes took a couple of tries for the student to get it right, but they did improve.

So, I came up with some guidelines that worked for this grading scheme:

• Make short writing assignments, 10 questions or fewer. One page is ideal (no scrolling).
• Assignments involve explaining a physics idea or ideas in words.
• Make all the assignments in an easy to grade format in Google docs.
• Give directions to the students for their response “Type your coherent, paragraph-length response in this box”.
• Use your judgment as to whether the answer is good enough. Make a rubric or scoring guideline before grading, to make sure that you are consistently grading.
• If a student misstates, misinterprets, or doesn’t use one of the ideas in a correct response, they must correct their answer
• Give students low grades (60%) and demand corrections before improving the grade.
• Write comments on each response to show them how to correct.
• If the corrections are not correct, write a more directed comment and ask them to redo. If there are lots of mistakes on a longer document, pick only the most important questions and only demand that they redo those.
• Grade fast so they can work on their modified response right away.

Here is an example of an assignment I wrote. Students learned this topic virtually. Below is the stem and the stimulus for part (a).

And here is the stimulus for part (b).

Below is a student’s modified answer to part (a) with my original comment. The blue check mark means that the comment was marked as resolved. The first attempt earned a grade of 60:

And below is the same students modified answer to part (b) with my original comment:

And here are the general comments between student and teacher.

Yes, the Google Classroom Learning Management System (LMS) makes this easier, but it could be done without it, using Microsoft Word’s reviewing features, for example.

The assignments were short, students knew they had the opportunity to revise and the feedback was (relatively) swift. A number of them seemed to improve in their writing as we went through the process of reviewing for the AP1 exam.

Modeling in AP Physics 1: Pacing Guide

A/B/C Block

Marc Reif

The AP1 Exam is Wednesday, May 5, 2021.

For 2020-2021 The students in AP Physics 1 will have had no previous physics course. Most had Pre-AP Biology or Pre-AP Chemistry in the previous your. Many are concurrently enrolled in PreCalculus, some in AP Calculus (usually AB), and a few will be in Algebra II or III. 

Instruction begins on Friday, 13 August 2020 Our school is on A/B/C block. Each class meetings two 82-minute sessions (A/B) and one 42-minute session (C) every week. We have about 160 meetings before the AP Exam. There are about 34 A/B meetings  and 13 C meetings in the first semester and 31 A/B meetings in the second semester and 12 C meetings before the AP1 Exams. That is 6380 minutes or 106 hours or 4.4 complete days of instruction.  So, first semester 47 actual class meetings and second semester 43 actual class meetings. 90 days of instruction before the exam. 

Text Eugenia Etkina College Physics 2nd Edition

Note: Observational Experiments derive physics from a series of observations. Testing Experiments test a hypothesis.

Unit 01 –  1d Kinematics Chapters 1 and 2	Constant Velocity Model, Constant Acceleration Model, 1d Vectors, Graphical Analysis, Measurement and uncertainty. Paradigm Labs Observational Experiment: Blinky Buggy (Constant Velocity Model) Observational Experiment: Fan Cart (Constant Acceleration Model)	2 weeks 6  meetings 13 Aug to 28 Aug
Unit 02 – Interactions I Chapter 3	Constant Force Model, Newton’s Laws, Reference Frames, Local gravitational force law, vector addition (primarily forces in one dimension) Paradigm Lab Testing Experiment: Fan Cart (Constant Force Model – intro to semi-quantitative vector components)	2 weeks  6 meetings Aug 31 – Sep 15
Unit 03 – Interactions II Chapter 4	Force vectors in two dimensions, Systems of Interacting Objects, Frictional force law Paradigm Labs Testing Experiment: Balanced Forces Practicum; Testing Experiment: Modified Atwood’s Machine	2 weeks 6 meetings Sep 15 – Sep 30
Unit 04 Impulse and Momentum Transfer Chapter 6	Conservation of mass, Conservation of linear momentum in one (quantitative) and two dimensions ( semi-quantitative),  impulse Paradigm Labs Observational Experiment: Modeling Collisions of Carts; Observational Experiment: Modeling Impulse and Change in Momentum	~2 weeks ~6 meetings Oct 1 – Oct 16
Unit 05 Energy Transfer Model Chapter 7	Work as energy transfer, models for energy storage, energy dissipation, energy and collisions Paradigm Labs Testing Experiment: Hooke’s Law and Elastic Energy Testing Experiment: Transfers to Kinetic Energy	2 weeks 6 meetings 19 Oct – 3 Nov
Unit 06 Models for 2d Motion Section 4.5, Chapter 5	Kinematics and dynamics of projectile motion, Uniform Circular Motion, Universal Gravitation and Orbits Paradigm Lab Observational Experiment: Projectile motion video analysis Observational Experiment: Behavior of objects in Circular motion	~3 weeks 11 meetings 4 Nov – 4 Dec
Semester 2
Unit 07 Models for Rotation Chapters 8 and 9	Torque and Semi-quantitative Rotational Statics; Rotational Kinematics, Newton’s Second Law for Rotation, Rotational Momentum, Rotational Kinetic Energy Paradigm Labs Observational Experiment: Balanced Torques Testing Experiment: Acceleration of a wheel	~3 weeks 10 meetings 6 Jan – 29 Jan
Unit 08 Models for Oscillation Chapter 10	Kinematics, dynamics, and energy models for mass-spring oscillator and pendulum Paradigm Lab Testing Experiment: Period of a Mass-Spring Oscillator	2 weeks 6 meetings 1 Feb to 12 Feb
Unit 09 Mechanical Waves and Sound Chapter 11	Wave pulses, traveling waves, standing waves, sound Paradigm LabsObservational Experiment: Wave PulsesTesting Experiment: Speed of Wave Pulses on a String	~3 weeks 11 meetings 16 Feb to 12 Mar
Unit 10 Electric Charge and Force Sections 17.1-17.4	Conservation of charge, Coulomb’s Law Paradigm LabObservational Experiment: Sticky tape	1 week 3 meetings (no test) 15-19 March
Unit 11 DC Circuits Chapter 19	Resistivity and Resistance, Ohm’s Law, Kirchhoff’s rules Paradigm Lab Observational Experiment:Potential difference in circuits	~3 weeks 8 meetings 29 Mar-15 Apr
REVIEW	NOTE: This is maybe not enough review, but don’t see how to go faster.  AP 1 Exam on Tuesday, 5 May 2021	~2 weeks 6 meetings 19-30 April

This sequence doesn’t EXACTLY follow the Unit Guides in the College Board’s AP Physics 1 Course and Exam Description. If next year, as they did this year, the College Board cuts off the last unit or more, I will have to flip Units 10 and 11 with Unit 9.

Even as I post this, I’m two weeks behind!! The Governor of Arkansas has pushed the first day of school back to August 24 due to the community spread of the Covid-19 virus in Arkansas.

Modeling in AP Physics C Mechanics – Pacing Guide

A/B/C Block Schedule

Marc Reif

The APC Exams are Monday, May 3, 2021.

For 2020-2021 The students in AP Physics C have about half had AP Physics 1, about half have not. Most (I think) are enrolled in AP Calculus AB or BC. 

Instruction begins on Friday, 13 August 2020 Our school is on A/B/C block. Each class meets two 82-minute sessions (A/B) and one 42-minute session (C) every week.

We have about 160 meetings before the AP Exam. There are about 34 A/B meetings  and 13 C meetings in the first semester and 31 A/B meetings in the second semester and 12 C meetings before the APC Exams. That is 6380 minutes or 106 hours or 4.4 complete days of instruction. 

So, first semester 47 actual class meetings and second semester 43 actual class meetings. 90 days of instruction before the exam. 

Text Randall Knight, Physics for Scientists and Engineers, A Strategic Approach, 4ed

Unit 01 – Tools Text Chapter 3 (vectors)	Vectors (including unit vectors), Graphical Analysis, Measurement and uncertainty, Scientific method, Calculus concepts and elementary methods.	<2 weeks 4 meetings 13 August to 25 August (optional unit)
Unit 02 -1d Kinematics Chapters 1 and 2	Constant Velocity Model, Constant Acceleration Model, Constant Jerk model, elementary calculus	~2 weeks (including test) 6 meetings August 26 – Sep 11
Unit 03 – 2d Kinematics Text Chapters 3 and 4	Projectile Motion, Uniform circular motion and Nonuniform rotational kinematics	~2 weeks 6 meetings (including test) Sep 14- Sep 29
Unit 04 – 1d Force Text Chapter 5-6	The Force Model	>2 weeks 8 meetings (including test) 30 Sept -16 Oct
Unit 05 – 2d Forces, Circular Motion Text Chapter 7-8	Applications of the force model, systems of objects, vectors (ramps, etc.), circular motion	>2 weeks ~6 meetings  19 Oct – 3 November
Unit 06 – Momentum Chapter 9	Momentum Transfer Model and Impulse	>2 weeks 8 meetings 4 Nov – 20 Nov This unit probably won’t require this much time, but this takes us up to Winter Break. Could stretch out earlier unit or could start energy earlier.
Unit 07 – Energy Chapter 10-11	Energy Transfer Model, power, potential energy functions	2 weeks ~6 meetings  (some Chap 10 energy concepts on semester exam) 30 Nov to 14 Dec
Semester
Unit 07 – Work Chapter 11	Additional applications in work and energy	~2 weeks 6 meetings 6 Jan to 20 Jan
Unit 08 – Rotation Chapter 12	Rotational Models	~3 weeks ~10 meetings 21 Jan to 12 Feb
Unit 09 – Gravitation Chapter 13	Gravitational Potential and Energy, elliptical orbits,	> 2 weeks ~8 meetings 16 Feb – 5 March
Unit 10 – Oscillation Chapter 14	Simple Harmonic Motion, Pendulums (simple and physical)	2 weeks 6 meetings 8 March – 19 March
	REVIEW – additional depth on Calculus topics	>1 month 14 meetings for review 29 March to 30 April

Modeling in AP Physics C Mechanics – Paradigms

A paradigm is a “model, pattern, example, exemplar, template, standard, prototype, archetype.” In modeling instruction, they are typically a demonstration or lab setup that serves to focus student attention on what is important in the unit. Paradigms are presented as the subject of a student-designed lab that is usually done at the beginning of the unit, and serves to help develop the conceptual model(s) for the unit. 

If in-person school is not possible, I intend to make short videos showing the data collection of each lab. Students will “collect” the data from the video and analyze it at home.  

Next year I will be teaching Mechanics as a full-year course, so there should be enough time to do all (or at least most) of these labs.

Unit 1:Kinematics

Lab 1 – Introductory lab – Three linear paradigms in one lab

Constant Velocity Model – Blinky Buggy toy moves with constant velocity 

Constant Acceleration Model (possibly with vectors) – Physics Fan cart moves with constant acceleration. Fan may be modified by changing angle and speed. 

Vernier Fan Cart

Non-constant Acceleration Model – Sliding Chain (over a pulley) breaking the constant acceleration model. 

Lab 2 – Another paradigm later on:

Circular Motion Model – (The Knight Textbook works a bit of circular motion into 2-d kinematics) – Rotating wheel slowing with constant acceleration. Probably use a Vernier Rotary Motion Sensor with an attachment. Another possibility is a bicycle wheel. 

Unit 2: Newton’s Laws of Motion

Lab 3 – Introductory lab

Constant Net Force Model – Fan Cart (with fan directed at angles for vectors). Develop Newton’s Second Law.

Labs 4 and 5 – Later on

Connected Objects Model – Atwood’s Machine, collect a data set using the materials from which the gravitational field strength of Earth can be derived. 

Pasco Atwood’s Machine

Non-uniform Force Model – Falling Coffee Filters (Is the drag force proportional to  v or v² ?)

Unit 3: Work, Energy, and Power

Lab 6 – Introductory lab

Energy Transfer Models – Work on a spring transfers to kinetic energy (with Pasco Spring Cart Launcher); Work on Earth’s g-field transfers to kinetic energy. Collect data with Dynamics Carts, Dual-Range Force Sensors and Motion Detectors. 

Pasco Spring Cart Launcher

Lab 7 – Later on

Energy Dissipation Model – Ball Bounce Lab. What does the position vs. time data of a bouncing ball tell us about energy dissipation?

Bouncing Ball Position-time data

image from Frank Noschese’s Blog 

Unit 4: Systems of Particles and Linear Momentum

Lab 8 – Introductory lab

Impulse-Momentum Transfer Model – Force-time during a collision and change in Momentum. Using dynamics carts,  Vernier Bumper-Launcher Kit (and maybe Pasco Spring Cart Launcher) 

Vernier Bumper Launcher Kit

Lab 9 – Later investigation

Modeling Collisions – Dynamics Cart collisions in one dimension

Unit 5: Rotation

Lab 10 – Introductory Lab

Extended Object Model – Rotational Inertia and Angular Acceleration. Vernier Rotary Motion Sensor and accessory kit again.

Vernier Rotary Motion Accessory Kit

Unit 6: Oscillations

Lab 11 – Introductory Lab

Simple Harmonic Oscillator Model – Dependent variables that affect period/frequency of a mass-spring system. I like Pasco Springs for this. Equal Length and Hooke’s Law Set. They look the same, but are different:

Pasco Equal Length Spring Set

Lab 12 – Later on

Physical Pendulum Model – Dependent variables that affect period/frequency of an extended object pendulum. Vernier Rotary Motion Sensor and Accessory kit, again. 

Unit 7: Gravitation 

Lab 13 –  Introductory Lab

Universal Gravitation Model  – Cavendish Balance (classroom demonstration, I don’t have the money to buy a balance that provides quantitative results). Thinking of either setting up my own for demo purposes, or showing the YouTube videos of other’s. 

Questions or comments? Other ideas? Please share!

Teaching with Modeling in AP Physics

Modeling is a student-centered, inquiry-based, very successful teaching method originally developed at Arizona State University and now maintained by the American Modeling Teachers Association.

The clearest evidence that AP Physics and Modeling are a great fit is seen in the AP Physics Science Practices. These are embedded in each course, outlining the skills that should be developed by the students. Each AP Exam question incorporates one or more Science Practices. This is described in detail in the Course and Exam Description for each course. There is a set of SPs for AP Physics 1 and 2 (see below), and a slightly different set for AP Physics C Mechanics and Electricity and Magnetism.

In this post, I’ll take you through the Science Practices for AP Physics 1 and 2, and I’ll list one example of a connection with Modeling for each practice.

Science Practice 1, Modeling

“The student can use representations and models to communicate scientific phenomena and solve scientific problems”

What could be more clear! Science Practice #1 is “Modeling” and the Modeling Method for teaching physics is about training students to see science as the process of constructing conceptual models to explain nature.

In teaching with modeling, students begin most units by examining paradigms (standard examples) of each model in a student-designed lab. The students represent the behavior of the paradigm with four types of representations, mathematical, graphical, pictorial, and verbal. That means Science Practice 1 is embedded in every Modeling unit right from the start.

Science Practice 2, Mathematical Routines

“The student can use mathematics appropriately.”

In AP Physics 1/2 this Science Practice is often used to indicate an exam question that requires calculations by the student. But it is also used to indicate cases where a student has to explain WHY an equation (or a graph) makes sense, or why a representation models a physical situation. Here is an example from the 2019 AP Physics 1 released exam questions:

In teaching with Modeling, we use classroom discourse to accomplish the same ends. The teacher (and even other students) ask deep questions that cause students to justify the graph that they constructed, or the mathematics that they used to solve a problem. The whole class participates in this discussion, so that everybody understands WHY the techniques that were applied to create the model or solve the problem make sense. I wrote this blog post describing some of the popular whiteboarding techniques.

Science Practice 3, Scientific Questioning

“The student can engage in scientific questioning to extend thinking or to guide investigations within the context of the AP® course.“

This science practice has three components:

3.1 The student can pose scientific questions.

3.2 The student can refine scientific questions.

3.3 The student can evaluate scientific questions.

In teaching with modeling, many units begin with a student-designed “paradigm lab.” Teachers demonstrate an interesting system, the “paradigm” (a pendulum, in one unit), and students (with lots of guidance and some limitations) choose what they want to investigate about the physics of the paradigm. Students pose observations and questions about the system in a whole-class brainstorm. They refine the questions in deciding what variables to test and how they can test them. And they evaluate the questions in the model-building discussion that follows the lab, where students decide what their lab results mean.

Typical graphs that students have to explain after the pendulum lab.

Science Practice 4, Experimental Methods

 “The student can plan and implement data collection strategies appropriate to a particular scientific question.“

On the AP exam, this is assessed in a question where students must design a lab to answer a question. In the modeling classroom, this is a component of nearly every unit. Modeling-trained teachers give students leeway to create and carry out their own labs. This is excellent practice for AP experimental questions.

Don’t try this at home!

Science Practice 5, Data Analysis

“The student can perform data analysis and evaluation of evidence.“

In modeling, students must frequently collect data, construct a table, graph the data, produce a mathematical model that represents the data (and the physical system), and then explain in their whiteboard presentation their whole process and findings.

A student group’s whiteboard

And here’s an example of how the AP Exam assesses the skills developed from teaching with inquiry and modeling, also from the 2019 AP Physics 1 Free Response questions:

Science Practice 6, Argumentation

 “The student can work with scientific explanations and theories.

Argumentation involves justifying, constructing explanations, making claims, and evaluating explanations. One place on the AP Physics Exam where this Science Practice is often assessed is the “Paragraph-Length Explanation” question. There is one of these on every AP Physics 1 and 2 exam. In the Paragraph Length Explanation question, students tie together several different ideas in physics to explain the behavior of a physical system. This is quite challenging!

Modeling students should be well-trained in these skills. The skilled modeling teacher is constantly demanding that their students justify and explain physics.

Science Practice 7, Making Connections

“The student is able to connect and relate knowledge across various scales, concepts, and representations in and across domains.“

Isn’t this the goal of all science teachers, but especially modeling science teachers? A great example of this is the placement of the projectile motion unit in the modeling workshop I attended. Instead of being in the first unit or two, projectile motion was placed in unit 6. This was so that students could use all of the tools they have been taught in the early units: graphical models, mathematical models, pictorial models motion maps (the infamous “dot diagrams” that bedevil so many students), free-body diagrams and the whole force concept. Instead of projectiles being a scary, painful assault of obscure equations, students see it in the context of the course. It becomes both easier to understand and less scary by this simple adjustment.

Here is an example (from the released 2018 AP Physics 1 Free-Response Questions) of how the AP exam assesses both Argumentation and Making Connections. In answering this question, students must put together two areas of physics: momentum and oscillation.

I hope this all makes sense. Please comment or ask questions if you feel the need.

Go to the AMTA website (modelinginstruction.org) and check out all of the resources for modeling, if you’re new to it. A modeling workshop is great background for teaching the Science Practices in AP Physics.

Marc Reif’s 2020 AP Physics Summer Institute Presenting Schedule

~hover over the text to find links to course, site, and geographic location~

Online! AP Physics  1 and 2 combined Registration Link on this page

Pamphlet here

15 June to 19 June 

University of Texas–El Paso

#####

Online! AP Physics C (Combined Mechanics and Electricity and Magnetism)

22 June to 26 June

Walton HS – Marietta, Georgia

#####

Cancelled. AP Physics C (Combined Mechanics: Electricity and Magnetism)

6 July to 9 July

University of North Texas – Denton

#####

Online! AP Physics 2

13 July to 17 July

University of Arkansas – Fayetteville

#####

Online! AP Physics 1 for New Teachers

20 July to 24 July

Rice University – Houston, Texas

######

Cancelled. AP Physics 2

27 July to 30 July

Silver State APSI

Liberty HS, Henderson, NV

Electricity Visualized! Teaching Circuits in AP1 with ideas from the CASTLE Curriculum.

CASTLE stands for Capacitor-Aided System for Teaching and Learning Electricity.

It is a conceptual curriculum available for download from Pasco Scientific (go to https://www.pasco.com/prodCompare/castle-kit/index.cfm and scroll down to find the downloads). The curriculum is a basically complete set of activities, demonstrations, student classwork, homework, and quizzes.

A teacher guide is available by contacting me (or Pasco Scientific).

It takes a lot of time for students to complete the whole curriculum, but there are benefits. The curriculum is student-guided and inquiry-based, and emphasizes deep conceptual understanding (there are virtually no calculations and equations). Because of time constraints, my students, even my students in “on-level” physics where there is less time pressure, don’t do all of the activities. I am presenting some of the useful ideas here, so that you can see the benefit of the curriculum and perhaps make use of some of the ideas even though you don’t use the whole thing (which would be ideal, but won’t work for everyone).

Any of these activities that use a capacitor and bulbs to visualize what is happening in a circuit will not work with ordinary capacitors. As far as I know, Pasco.com is the only source for the capacitors that are utilized in the CASTLE curriculum. But, many of the activities below do not require the CASTLE capacitors. 

1.2 Activity:  “Using the compass to investigate a closed loop.”

A compass is placed under one of the wires in a circuit. 

• The deflection of the needle indicates something is happening in wires.
• Reversing the battery reverses the deflection – whatever is happening has a direction.
• Moving the compass to different parts of the circuit shows the same deflection – indicates that whatever is happening in the wires happens everywhere. Charge is everywhere in the circuit. The battery provides energy that makes charge move/causes charge to do work, but is not the source of charge (See also Activity 8.1).

1.11 Activity: “Lighting a bulb with a single cell”

Students are given a miniature bulb, a D cell and a single wire. They are challenged to light the bulb using only those materials. Students are given a “dissected” light bulb to examine. 

• An incandescent bulb must provide a single conducting path for charge to move through the bulb, including the filament
• Charge must enter and leave through conducting parts of the bulb
• Insulating parts of the bulb separate the conducting parts to provide the single path

2.3 Activity “Additional Symbols for Circuit Diagrams”

Try drawing “starbursts” to represent bulb brightness:

And drawing “Arrowtails” to represent current magnitude and directions:

2.6 Activity “Examining filaments under magnification” and 2.8 “Comparing the resistance of a bulb to a wire”

This is done after students observe that adding resistors or bulbs in series to a circuit decreases the brightness of a bulb. They examine the filaments of incandescent bulbs using magnifying lenses. The filament wires are much thinner than the support wires and connecting wires (alligator clip leads). Adding a long wire to a circuit does not appreciably change the brightness. Connecting a wire in parallel with a bulb causes the bulb to go out, as nearly all of the flow stays in the wire. Students deduce that most of the resistance is in the bulb.

• Most of the resistance is in the bulb
• The filament of the bulb is much thinner than other parts of the circuit
• Thinness appears to equate with increased resistance
• In a series circuit, a long bulb is brighter than a long bulb – since current is the same in the series circuit, the brightness of the bulb must depend on the resistance of each bulb. The filament of the round bulb must have less resistance than the filament of the long/the filament of the round bulb is thicker than the filament of the long bulb a thin filament has high resistance (see pictures below)

Round bulb (image by Charles Mamolo)

Long Bulb (image by Charles Mamolo)

2.7 Activity “Detecting the resistance of straws to air flow”

In this activity different sized straws are used as an analogy for conductors in a circuit. Air is a compressible fluid that serves as the analogy for electric charge in the circuit. Coffee stirrer straws, ordinary drinking straws, bubble-tea straws, and paper towel tubes are all useful for this activity. Students blow through the straws and observe that resistance to airflow decreases with diameter. Putting like straws together with tape illustrates the series and parallel relationship with resistance. 

• Resistance to flow decreases with increased diameter
• Resistance to flow increases with increased length
• Resistance to flow decreases when “resistors” are arranged in parallel, increases when they are arranged in series.

2.8 Activity “Comparing the Resistance of Wire with a Filament”

Students insert a long wire into their circuit and observe that the compass needle deflects the same as before. Then they insert a second bulb in series into their circuit, and observe less deflection. This leads to the conclusion that wire has negligible resistance and bulbs have significant resistance. 

4.2 Activity “Exploring air as an analogy”

Two linked hypodermic syringes (minus needles) show how pressure equalizes in a circuit. Potential difference (voltage) in a circuit acts like pressure differences in the syringes. 

• When circuit elements are connected to a source of electric pressure (a battery, for instance), the pressure quickly equalizes
• Although the elements may be different, the pressure equalizes if it can. 

4.7 Activity: How below-normal air pressure behaves (Air Capacitor)

In this activity, students work with an air capacitor (shown above in schematic and below in a photograph).

Blowing air in or out causes the balloon membrane to move, displacing air and/or changing the pressure within the capacitor. This is analogous to the flow of charge into and out of a capacitor. Air/Charge is already present in the capacitor, and is displaced from one side or the other, rather than moving through the capacitor. The balloon membrane acts like a dielectric, insulating one side from the other. 

4.9 Commentary “Color Coding for Electric Pressures in a Circuit”

In this section, students use colored pencils to represent levels of electric potential in a circuit by color-coding schematics of the circuit. Once students understand what is expected, it is very quick to determine which bulbs in a circuit will be the brightest, or identify any bulbs that will not light (because both ends are at the same “electric pressure”). Try color-coding this circuit: 

See below for a CASTLE-style representation of an RC circuit charging. 

8.1 Activity “Circuit with a Conducting Island”

Build the circuit, predict what will happen, and connect it. The bulbs light and then go out. Charge that lights the bulbs must not have come from the battery, since the capacitor has insulators that don’t let charge through. Charge everywhere in the circuit moves until the electric pressures are all equalized. Energy is stored in the capacitors when they charge, but not a net charge. 

Conclusion

There are twelve sections in CASTLE. The later sections delve into advanced topics, such as electric fields, semiconductors, magnetism and induction, and electromagnetic signal propagation and detection. All without making significant use of mathematics and equations. There are great teaching ideas in those sections, I just chose to highlight some sections that may be more broadly applicable.

You can download the curriculum from Pasco.com. Or leave me a message below /send me an email and I can share the entire curriculum, including a few things that are not available on the Pasco website.

Pasco Scientific is a convenient source of good-quality materials for the CASTLE kit used by students in the curriculum. You may be able to find everything in the kit cheaper elsewhere, but the capacitors. I have never seen those specific capacitors (High Capacitance, relatively high Voltage, and non-polar) anywhere else. 

PEER INSTRUCTION

I learned a very simple, powerful technique for engaging students’ interest, sparking intense classroom discussions, and guiding students how to think like a physicist from the book Peer Instruction  by Eric Mazur. What’s more, if you use this technique in AP Physics you’ll be incorporating a version of scientific argumentation into your instruction, something the College Board says we must be doing in AP Physics.

It’s a skinny volume, but it does contain a description of the Peer Instruction method, a discussion of the results of using PI, “Climate Setting” tools (techniques for getting students to buy in to inquiry) and ConcepTests for using PI in an introductory physics class.  There is good advice in here, but I will get you started using this technique right here.

The Peer Instruction technique is fairly simple to describe and has been discussed in many places (see here, and here, for example). This post is an outline of how I use this technique, with some tips from my experiences with high school students.

Step 1. Present to students an interesting multiple choice, conceptual question.

Paul Hewitt’s Next-Time Questions contain many great examples (the link takes you to Arbor Scientific’s website where you can download all of them; or, send me an email and I can send you a link to my Google Drive folder of them all). In the example above, students would vote  (A) for 100 N, (B) for 200 N, (C) for Zero N.  I usually project the question. If you are a non-physics teacher reading this post, I can assure you that physics students will get into a very intense discussion about the question above.  

Step 2. Students silently read the question, and the teacher collects the anonymous responses.

My current favorite approach for gathering the responses is Plickers (“paper clickers”). Plickers are free, and fast. Students are assigned a card with a number and a pattern on it. They vote by holding up the card in one of four possible orientations, while a phone or tablet scans the room. They can change their answer on the fly, and the website records their responses. This usually takes only about 2 minutes, including scanning the plickers.

 

image from https://plickers.com/

Other high-tech methods include socrative, polleverywhere,  or dedicated remote answering systems (“clickers”).

Low-tech approaches include students voting with a stack of colored plastic cups, colored post-it notes, colored index cards, or a show of hands. These are not as good, because they are not anonymous. Some students will hesitate to vote, or just as bad, copy their neighbor’s votes. You want everybody voting their own ideas so you have the option of discussing all ideas!  

Step 3. The class views the first graph of responses.

A good question will have some respondents on every (or nearly every) choice. For the plickers website,  I have created generic (no text, no image) 2, 3, and 4-choice questions that I use over and over again, rather than typing the question text into the plickers library. The graph after responses are collected from plickers.com looks like this:

Notice the vote with plickers is anonymous. I can’t stress enough how much this improves discussions. If the vote is by a show of hands, for instance, watch your students and you will see them hesitate until others have voted, or change their vote based on what their neighbors are doing. This is not what you want! You want all ideas represented in the discussion. I either place my phone under the document camera, or switch to the Plickers website “Live View” to display the graph. If I have to use the low-tech approach, I always sketch the bar graph of the responses I see on the board. This step takes about 30 seconds.

Step 4. Students discuss their own answers and the first class graph with their neighbors.

This takes several minutes on most questions, and  longer on a tough question or ambiguous question. Tell your students they must use physics to convince their neighbors what the right answer is. This is where the real power of the approach comes in. Everybody (hopefully) has committed to an answer and (again hopefully) has something to discuss. Looking at the graph is a powerful moment where they realize there are multiple ideas out there. You want them to discuss. Even discussing a guess is likely to be better than just listening to other people. Make sure everybody talks physics during this time.  The teacher roams and discusses with various groups. This is your opportunity to ask probing questions, force students to defend their reasoning, make sure everybody is engaging in the argumentation. Move quickly and check in with everybody you can. Help guide their discussion by asking “interesting” questions when they are stuck. This will also help you gain a sense of which groups to call on for Step 7. You may want groups to explain both correct and incorrect reasoning. It is important not only that students understand what makes a correct answer correct, but what makes an incorrect answer incorrect.

Step 5. Students answer again, after agreeing with their neighbors on an answer.

I command “Hold up your card for your second answer, and you better be prepared to defend your group’s answer!” This takes another 30 seconds.

Step 6. The class views a graph of the second set of responses.

Really good discussions in Step 4 may lead to nearly everybody switching to the best answer. This doesn’t happen every time. Sometimes they nearly all switch to what is not the best answer! That is also an opportunity for a good discussion. If the responses are still dispersed, you can decide, based on the quality of the discussions in the groups, to have them discuss again, and vote again. This might be a point where you provide a strong hint. For instance, in discussing the Paul Hewitt question above, a lot of students might decide that the best answer is 200 N. If this is the case, I might say to the class “If the tension is 200 N, do the masses remain at rest? Discuss again, and we’ll vote again!”

Step 7. A whole-class discussion on the final set of responses, with the goal that the class decides what is the best answer.

Have some student or students explain the reasoning for every choice, if you feel you have time. If time is short, or the discussion is dragging, you may quickly explain to the class what you heard from the groups about some choices. For instance, I might say “I heard that everybody excluded Zero newtons as the answer because everybody was sure you could feel some tension in the string, so let’s not discuss that one.” I try to get the students to reach consensus, without needing me to tell them the answer. A representative speaker is called on to defend their answer, and they are encouraged to engage in some (respectful) back-and-forth about what is the best reasoning. I try my hardest to stay out of the discussions as much as I can, interjecting only when I feel it is necessary. At the end, I try to never give up an answer, but I will say “It’s time to move on” when I feel that no more discussion is necessary. At this point they may demand an answer, but I repeat “I’m ready to move on.” Some kids really want me to explain the answer to them again, but what’s the point? They’ve already heard the answer.  If a student doesn’t get it, usually another student will say to them “Whatever we last said was right, or he wouldn’t be ready to finish.”

If a student asks, I would take the time (or have a student take the time) to summarize the reasoning we agreed upon by writing it on the whiteboard. But I don’t often initiate this. In my mind the discussion is the goal, not memorizing a solution.

I never grade these discussions for accuracy,  although I often keep track of who contributes to the discussion using ClassDojo.

Peer Instruction Links

Wikipedia page

 

YouTube video of Peer Instruction in use

 

 

YouTube video with Eric Mazur talking about PI

Peer Instruction blog

Peer Instruction network (nothing much there, yet)

A paper on Peer Instruction in Calculus

The Amazon page for the book

“Nothing is too wonderful to be true” – Michael Faraday’s Law

By Thomas Phillips (Thomas Phillips, 1842) [Public domain], via Wikimedia Commons

Science is moved forward by observations and experiments, yet some observations are too subtle and some experiments too complicated to reproduce in the classroom.Michael Faraday’s discovery of electromagnetic induction combines observation and experimentation yet requires nothing expensive or complicated. It is intriguing, easy to reproduce, and provides insight into the intellectual leap from observation to model-building.

The equipment is economical enough that many teachers could buy a set for every student. Below is a picture of the equipment I use when I do this as a demonstration. The stuffed gorilla is not absolutely necessary.

Batteries can be substituted for the power supply, the primary-secondary coil set comes with the core and costs less than fifty dollars, and a small galvanometer costs less than ten dollars.

The procedure is extremely simple, and mirrors Faraday’s. In class, we have already observed that electric charge moving in a wire produces a magnetic influence around the wire, which deflects a compass needle. This is known as “Oersted’s Law.” To begin the activity I raise the question, “If moving charge in a wire can influence a magnet, can a magnet make charge move? It seems likely, doesn’t it?”

At this point I’d introduce the apparatus. The galvanometer is a sensitive, uncalibrated meter. If an electric current runs through it, the needle deflects in one direction. If a current runs through in the opposite direction, the needle deflects in the opposite direction. The secondary coil has a lot of turns of fine copper wire. When we connect the galvanometer to the coil, we have made a device that can detect the motion of small amounts of charge within the coil.

I start out by showing when the galvanometer needle doesn’t deflect. Inserting one coil in the other does nothing. Inserting the core may make a small deflection, if your core is slightly magnetic, like mine. Inserting or dropping a small magnet through the coil makes the needle deflect first one way, and then the other. A moving magnetic field can make a current flow!

The real excitement occurs when you energize the coil that is not connected to the galvanometer by running a small electric current through it. Then insert it into the other coil. The galvanometer needle will deflect very noticeably, and even more so when the core is inserted into the energized coil, which becomes an electromagnet. The magnetic field of the moving charge in the energized coil has caused charge in the other coil to move in an electric current. Any change in the magnetic field in the primary coil causes charge to flow in the secondary coil. This phenomenon is known as electromagnetic induction, and its discovery is one of the most consequential discoveries in the history of science. Electric motors, generators, and transformers all depend on it. Our modern technological society owes as much or more to this discovery as any other.

This is a moment for the teacher to act a bit, and show real enthusiasm or feign surprise. The deflection of a tiny needle is neither explosive nor glamorous. You have to be excited or students will not get it. Channel the excitement of Michael Faraday when he made the original discovery after years of work. Proceed to show the effect of changing the current through the energized coil, adding the core, and moving the two coils at different speeds relative to each other. Note that the direction of the galvanometer needle motion is tied to the direction of the motion of the coils relative to each other.

Pretend to be finished. Turn the power supply off, and say “Hey, did you see that! The needle really jumped when I turned the power off.” Turn the power supply on again, and be surprised when the needle jumps in the opposite direction.

Much later, all of these observations were summarized as Faraday’s Law by incorporating the magnetic flux model, but I suggest not jumping right to the equation. Take a few minutes to talk about the excitement Faraday must have felt, and the trepidation at explaining such a mysterious phenomenon. What one model could explain all of these different observations? How would you explain it? Perhaps you will introduce magnetic flux later, but put students in Michael Faraday’s shoes for a few minutes.

Faraday wrote these words much later:

“ALL THIS IS A DREAM. Still examine it by a few experiments. Nothing is too wonderful to be true, if it be consistent with the laws of nature; and in such things as these, experiment is the best test of such consistency.”

Laboratory journal entry #10,040 (19 March 1849); published in The Life and Letters of Faraday (1870) Vol. II, edited by Henry Bence Jones [1], p. 248.

I made a short video of this demonstration, if you’d like to see me perform it (albeit without students). PhET Interactive Simulations has two excellent, free simulations that help students visualize what they have seen in the demonstration. Faraday’s Law (written in HTML5, so it runs on nearly all devices) and Faraday’s Electromagnetic Lab (which was written in Java, so it will not run on some devices).

Michael Faraday is one of the most important 19th century scientists, yet he was a of paradox. He began his scientific career as a lab assistant and rose to head the Royal Institution. Known for his careful observational experiments, he originated theories that are considered the crowning scientific achievement of his time. Briefly schooled, he knew little about mathematics, yet his ideas led to a mathematical synthesis of the cutting edge physics of his day, the theory of electricity and magnetism. The ring which he used to first observe electromagnetic induction is below:

by Paul Wilkinson, from the Royal Institution of Great Britain

The Electric Life of Michael Faraday by Allan W. Hirshfield is a very readable, relatively short account of his life and work.

You can read Michael Faraday’s original lab entry on the induction ring on this page at the Royal Institution website.

Veritasium made an excellent video in which the host, Derek Muller, visits the Royal Institution and views Faraday’s equipment where he used it.

In AP Physics 2,the relevant College Board Learning Objective is

4.E.2.1: The student is able to construct an explanation of the function of a simple electromagnetic device in which an induced emf is produced by a changing magnetic flux through an area defined by a current loop (i.e., a simple microphone or generator) or of the effect on behavior of a device in which an induced emf is produced by a constant magnetic field through a changing area. [SP 6.4]

And in AP Physics C Electricity and Magnetism:

“b) Students should understand Faraday’s law and Lenz’s law, so they can:

1) Recognize situations in which changing flux through a loop will cause an induced emf or current in the loop.

2) Calculate the magnitude and direction of the induced emf and current in a loop of wire or a conducting bar under the following conditions:

1. The magnitude of a related quantity such as magnetic field or area of the loop is changing at a constant rate.
2. The magnitude of a related quantity such as magnetic field or area of the loop is a specified non-linear function of time.”