This was my last year to teach Gauss’ Law early in the course

The Matter and Interactions textbook has it right by bundling Gauss’ Law and Ampere’s Law together near the end of the E&M section of the book. I don’t think either of these topics belong in the introductory course at all (actually I don’t even think E&M topics belong in first year period). But since my hand is currently forced, Gauss’ Law will be a topic for the last couple of weeks in my future intro E&M courses.

Trying out a new type of simulation-based pre-class assignment

I always had trouble picturing the ground state of the deBroglie model of the Hydrogen atom. Now I don’t!

At this past week’s Global Physics Department virtual meeting Noah Podolefsky spoke with us about PhET simulations. Noah’s best practice suggestion was to let students play around with a simulation for 5-10 minutes before asking them to do anything specific. And when you ask them to do something specific, to use open / investigative questions (e.g., “explore all things that affect pH”, as opposed to cookbook directions such as “set the acid concentration to 0.010 M…”).

I asked Noah

I’m wondering how you would suggest using these in pre-class (JiTT-style) assignments. If I am ultimately going to give them some sort of a question (could be nice and open like you suggest), I feel like most students will jump to try to answer the question without first doing the “free play”. Any suggestions on getting them to do “free play” first?

Noah suggested getting them to play around with the sim and generate 2-3 questions or screenshots of “cool things” that they found, which Brian Frank echoed by suggesting I do the same thing I did when I got my Quantum Mechanics class to generate questions based on a reading. Andy Rundquist also suggested I could get them to screencast their interesting discoveries (instead of just screencapping).

My Quantum Mechanics class is in the middle of developing the Hydrogen wavefunctions (I showed them the shooting method results for the angular wavefunctions last class, thanks Andy!).  We’re skipping our regular pre-class assignment this week, so I sent them a bonus pre-class assignment before we look at the Hydrogen spectrum on Monday. Here’s a slightly paraphrased version of what I asked them to do with the “Models of the Hydrogen Atom” PhET simulation:

Spend 5-10 minutes playing around with the simulation. Generate 3 items of interest — these could be any combination of questions that you have, interesting observations that you made or descriptions of things that the simulation made really clear to you that you didn’t quite get before. You can take screen captures, generate screencasts or just send me regular old text.

I’m really interested to see what they come up with. I will make sure to report back.  Just for fun, I have embedded the simulation below

Models of the Hydrogen Atom

Click to Run

Using review homework assignments to minimize class time spent on review topics

One of the many great ideas that I use from the University of Colorado Physics department is to start my 3rd-year Quantum Mechanics course off with a review assignment. On the first day I gave them an assignment which was due on the second day and had questions addressing the major relevant things that they should know coming into  this course based on their prerequisites.

It consisted of some fairly straight-forward review questions on topics such as complex numbers, matrix multiplication, dirac delta functions, the relationship between energy and frequency for light, orthogonal functions, the deBroglie wavelength and basic discrete probability.

But what really makes this work is that you ask them to include, along with their solutions, a rating for  each question on the following scale (credit goes completely to the University of Colorado folks that put the original assignment of this type together for these ratings):

  1. I knew this material, it was fairly trivial for me.
  2. I knew this material, and didn’t need to look up anything or get help, but it was not what I would call “trivial” for me.
  3. I knew this material, but still need to look something up in a book/notes or on the internet.
  4. I knew this material, but still need to get help from a person.
  5. I did not know this, and had to learn it for this homework.

I really like this system for multiple reasons. It communicates to them that there are some things that they should know from their previous courses and we are not going to use class time to review it. And if for some reason they have completely forgotten that material or never learned it in the first place, that they are in a position to go out and use the resources at their disposal to learn it. It is also a bit of a reflection exercise in that there are students that probably don’t realize how much help they ask for with their assignments and having to rate how much help they got might be a bit enlightening to them. And, of course, their rating of each question gives me a much better understanding of where everybody in the class stands coming in compared to if I just gave them the review assignment without asking them to rate the questions. This is related to the common issue of never knowing how much a student’s written homework represents their true level of understanding.

As for the idea of the review assignment in general. It won’t work that great if every single class they are taking has one, but since they typically have very little homework in the first week, asking them to do this first assignment in two days was very reasonable. It also saves me some class time and sets us up to immediately challenge more difficult things in class instead of always having to go through some review first.

Note: The University of Colorado shares all their course materials for their intermediate and upper-division reformed courses (Classical Mechanics, Quantum, E&M), including the review homework assignment that I adapted slightly based on my students’ prerequisites coming in.

Peer Instruction Fail

(This is not a criticism of Peer Instruction. It is just a tale of one of those times where the right idea failed to gain traction)

Yesterday we tackled a classic parabolic motion conceptual question in class, “three ships”, shown below.

They answered this question in their pre-class “reading” (actually I’m using smartPhysics so they watched a multimedia presentation). I am teaching two sections (35 students each) and will just combine their data here. On the first in-class vote, they were 51% correct. After discussion (5 minutes in one section, just about 10 minutes in the other), they revoted and were only 59% correct, which is a learning gain of 0.16 for those who like to use learning gains on clicker questions.

And the discussion was super animated. It seemed like it was so productive, but I guess it was really more about the two sides (B vs. C) digging their heels in.

And this does happen on occasion with Peer Instruction. You see 50% correct on the initial vote and smile to yourself thinking that the subsequent peer discussions is going to be a good one, but then sometimes the number of correct answers barely budges on the revote.

In the case of this question, it seems like I need some scaffolding clicker questions or other activities leading up to this question. Perhaps this scaffolding won’t improve the initial vote, but will perhaps give them more points of reference and examples to use in their discussions, helping the peer instruction really do its job.

Before coming to this question we spent 20-30 minutes developing position and velocity graphs in the horizontal and vertical directions starting from a motion diagram of a basketball shot, but did not talk explicitly about time at all during the sequence. Then we discussed the clicker question for the horizontal projectile vs ball drop demo  and they were nearly unanimous in getting that question correct. But it seems like more scaffolding is still in order.

Great student questions generated from Postulates of Quantum Mechanics reading

In my 3rd year (intro to ) Quantum Mechanics course the first homework assignment I gave them was meant to serve as a mostly gentle review of probability and modern physics as is relevant to the first chapter of Griffiths.

But I also asked them to read an 8-page section of some supplemental notes prepared by Michael Dubson and Steve Pollock at CU-Boulder (they can be found in the “Lecture Notes” folder of the “all course materials EXCEPT assessments” link on this page). These notes talk explicitly about the postulates of quantum mechanics (which Griffiths does not), about postulates in general and they compare and contrast classical and quantum mechanics.

As part of that first homework assignment I asked my students to read these notes and gave them the instructions:

Please write one or two questions that were burning in your brain after you read these pages.

And they gave me some wonderful questions which should provide us with some rich discussion on Monday. Here they are:

  1. I’m very confused how a wavefunction can change instantly after a measurement has been made on it’s position. (note: several variations of this question showed up)
  2. What reasoning did Schrodinger have for writing down his equation? (note: several variations of this question showed up and one student noted that it looked a lot like an equation he had seen in our PDEs course)
  3. Why is gravity proving to be so difficult to incorporate into quantum theory?
  4. Do quantum and classical mechanics agree with each other in predicting the outcomes of physical phenomena at a particular intermediate scale between the quantum scale and the macroscopic scale?
  5. Why does Planck’s constant have that specific value?
  6. Does the wavefunction ever reconstruct itself after being collapsed due to an observation?
  7. How come taking measurements changes the look of the wavefunction? It almost looks like a dirac delta function in the after measurement graph shown.
  8. (edited for brevity) Since real-world sized objects are made up of large quantities of microscopic particles shouldn’t the (quantum) laws and properties that govern the small not also govern the behavior of the large, which are really just big groups of the small? Why would we get different physics looking at many than looking at one?
  9. If x and p are not well-defined for a point particle, how does putting a group of them together suddenly make them defined for the group? how many does it take? Two? Three? Four billion trillion? At what point does a system become macroscopic?
  10. Where did the notion of wave-particle duality originate?
  11. How valid is string theory and a fundamental level?
  12. How does a measurement give the particle a definite position?
  13. How does Psi-squared represent the probability that a particle is at a specific location when we are told that Psi only “carries information about the particle, it is not ‘the particle’ or ‘the position of the particle'”?

Fantastic! Now they’re curious. And I’m not great at establishing a framework that ties together the ideas in a course, but I think that these questions mostly provide that framework and it was them that generated it instead of me. It’s their framework! I am thrilled.

Walking the interactive classroom walk right out of the gate

Executive summary: This year I’m going to get my intro mechanics students to make motion diagrams and we are going to play “match the graph” games with motion detectors on the first day of class. This is going to happen instead of me spending the whole class period telling them how the course is going to work and then actually starting in with an interactive classroom on day 2. How novel!

First day of classes = kind of awkward

One thing that has bugged me about my courses over the past couple of years is that my first class ends up being a mostly administrative/logistical introduction to the course, with lots of salesmanship and my regular level of being silly on top. I spend most of the time that day talking and there is a huge disconnect since what I’m talking about is all the ways that they are going to learn that don’t involve me talking. Yuck!

Part of why I do it this way is because I am a big advocate of pre-class assignments/some sort of flipping of my classroom (using reading assignments, screencasts or other multimedia). I have touched on these things before (here and here). In terms of consistency, it seems inappropriate to stomp around telling them that I want them to ALWAYS come to class prepared to build on the concepts from their pre-class assignments, and then start trying to teach them Section 1.1 on the first day outside of my regular flipped framework.

But in terms of an interactive classroom, day 1 is me talking the talk, but not walking the walk.

My new plan is to jump right in

But this morning I decided I’m going to change it up this year. I’m going to introduce myself, tell them that I (heart) the interactive classroom and jump right into something fun and learningful (I’m allowed to make up these types of words).

I think they think the students are supposed to show up already having a physical feel for motion

Most introductory physics textbooks jump into 1D motion right away, perhaps with a preceding chapter on units, vectors and other physics-support stuff. But what they don’t do is try to spend some time helping the students develop a feel for motion. Perhaps students can quickly go from from an x-t graph to a v-t graph, but have they developed a physical sense of what sort of motion something is undergoing if they see a parabolic v-t graph? Knight does a decent job of some of this. He spends time on making motion diagrams (the picture that you be created if the moving object dropped a breadcrumb once per second, similar to a strobe image). But it is ultimately up to the students to develop a physics sense of these motion quantities and how they interact with each other, and most textbooks don’t even try set the students up to do this; they just treat this physical sense as developed from the get-go. By the way, I am using smartPhysics as my text this year (as I discuss here) and their text is no different in this way.

It is interesting that, under my new plan, it is almost better that the textbook doesn’t try to help the students develop this physical sense of motion. That means that I can jump right into some “developing a physical sense of motion” activities on day 1 without undermining my usual structure of doing some learning from the text before class and then coming to class to refine and build on that learning. Thanks textbooks.

The actual jump right in activities I am mulling over

Motion diagrams – The first thing I am going to do is to walk across the front of the room at constant velocity, saying “now”, once per second and ask them to whiteboad a picture that represents where I was each time I said now. Then through some combination of whiteboarding, clicker questions and me running around at the front rhythmically shouting “now” we explore what the motion diagrams look like if I am speeding up, slowing down, going in one direction vs. the other or just standing still. In the middle of all of this I can introduce the idea that velocity can be represented by an arrow drawn from one dot on the motion diagram to the next. Perhaps Dan Meyer’s WCYDWT basketball shot will make an appearance.

Games with motion detectors – This is super fun and a great way to help students develop a physical feel for all the motion quantities and how they are related. Put them in front of a motion detector and give them an x-t, v-t or a-t graph and ask them to move their bodies to reproduce that graph. Through this process they get to relate their own physical motion to all three graphs and how they are related. Note that I have never actually done this in my own classes, but have done it as a participant at a workshop and loved it!

These would be tough for a student to reproduce by running around in front of a motion detector. They are from throwing a basketball up in the air and then catching it again.

Generating buy-in by walking the walk

I believe that generating student buy-in is the single most important factor in running a successful interactive classroom. And jumping them right into whiteboarding and learningful clicker questions (instead of starting with “what is your major” clicker questions) seems like it can only help to generate buy-in.

Since I usually spend an entire class period talking to them about the course structure, there must still be a bunch of stuff that I need to communicate to them early in the course, if not on day one. And this is very true. I’m just not going to front load it. What I am now planning on the first day is not going to show up on their first homework assignment (partially true, they probably will have to translate between x-t, v-t and a-t graphs), so I can wait until the second day to talk about homework. Their first quiz isn’t until day 5 so I’m sure I can wait until day 3 to talk about that. I’m going to embrace the 5-minute maximum that has imposed on the world and not talk, for more than 5 minutes at a time, about anything related to course logistics.

A last note

Just in case you think it is ridiculous that I seem so handcuffed to and by my textbook I want to state my position. If I am using a specific textbook for a course, I like to try to follow its sequencing and notation/conventions as much as possible. If I am going to ask them to try to do some initial learning out of the textbook, I don’t want to make their lives more difficult by making them jump ahead 4 chapters to a place where they vaguely mention ideas that came up in the 4 chapters that we jumped over, and then jump back 3 chapters to cover the stuff that we skipped later. Same thing goes for the notation and conventions: if they are going to see something written in their book umpteen times while trying to make first contact with an idea, I don’t want to further add to their cognitive load by completely switching up the notation and conventions.

A second last note

This post was supposed to be short. I have no idea what my problem is.

Resources for selling and running an (inter)active intro physics class

This post is in response to Chad Orzel’s recent post about moving toward a more active classroom. He plans to get the students to read the textbook before coming to class, and then minimize lecture in class in favour of “in-class discussion/ problem solving/ questions/ etc.” At the end of the post he puts out a call for resources, which is where this post comes in.

There are three main things I want to discuss in this post, and (other than some links to specific clicker resources) they are all relevant to Chad or anybody else considering moving toward a more active classroom.

  1. Salesmanship is key. You need to generate buy-in from the students so that they truly believe that the reason you are doing all of this is so that they will learn more.
  2. When implementing any sort of “learn before class” strategy, you need to step back and decide what you realistically expect them to be able to learn  from reading the textbook or watching the multimedia pres
  3. The easiest first step toward a more (inter)active classroom is the appropriate use of clickers or some reasonable low-tech substitute.


KNA, a commenter on Chad’s post writes:
I also realized early on in my career that salesmanship is key. I need to explain why I want them to do the reading, and the 3 JiTT (ed. JiTT = Just-in-Time-Teaching) questions, and the homework problems sets, etc. My taking some time periodically to explain why it is all in their best interest (citing the PER studies, or showing them the correlation between homework done and exam grades), seems to help a lot with the end of term evals.

And I completely agree. I changed a lot of little things between my first and second year of teaching intro physics, but the thing that seemed to matter the most is that I managed to generate much more buy-in from the students the second year that I taught. Once they understood and believed that all the “crazy” stuff I was doing was for their benefit and was backed up by research, they followed me down all the different paths that I took them. My student evals, for basically the same course, went up significantly (0.75ish on a 5-point scale) between the first and second years.

A resource that I will point out for helping to generate student buy-in was put together for Peer Instruction (in Computer Science), but much of what is in there is applicable beyond Peer Instruction to the interactive classroom in general. Beth Simon (Lecturer at UCSD and former CWSEI STLF) made two screencasts to show/discuss how she generates student buy-in:

Reading assignments and other “learning before class” assignments

This seems to be a topic that I have posted about many times and for which I have had many conversations. I will briefly summarize my thoughts here, while pointing interested readers to some relevant posts and conversations.

When implementing “read the text before class” or any other type of “learn before class” assignments, you have to establish what exactly you want the students to get out of these assignments. My purpose for these types of assignments is to get them familiar with the terminology and lowest-level concepts, anything beyond that is what I want to work on in class. With that purpose in mind, not every single paragraph or section of a given chapter is relevant for my students to read before coming to class. I refer to this as “textbook overhead” and Mylene discussed this as part of a great post on student preparation for class.

I have tried reading quizzes at the beginning of class and found that it was too hard to pitch them at the exact right level that most of the students that did the reading would get them and that most of the students that didn’t do the reading wouldn’t get them.

Last year I used a modified version of the reading assignment portion of Jitt (this list was originally posted here):

  1. Assign reading
  2. Give them 3 questions. These questions are either directly from the JiTT book (I like their estimation questions) or are easy clicker questions pulled from my collection. For the clicker questions I ask them explain their reasoning in addition to simply answering the question.
  3. Get them to submit via web-form or email
  4. I respond to everybody’s submissions for each question to try to help clear up any mistakes in their thinking. I use a healthy dose of copy and paste after the first few and can make it through 30ish submissions in just over an hour.
  5. Give them some sort of credit for each question in which they made an effortful response whether they were correct or incorrect.

I was very happy with how this worked out. I think it really helped that I always responded to each and every one of their answers, even if it was nothing more than “great explanation” for a correct answer. I generated enough buy-in to have an average completion rate of 78% on these assignments over the term in my Mechanics course last time I taught it. I typically weight these assignments at 8-10% of their final grade so they have pretty strong (external) incentive for them to do them.

As I mentioned previously, my current thinking is that I want the initial presentation (reading or screencast) that the students encounter to be one that gets them familiar with terminology and low-level or core concepts. As Mylene says “It’s crazy to expect a single book to be both a reference for the pro and an introduction for the novice.” So that leaves me in a position where I need to generate my own “first-contact” reading materials or screencasts that best suit my needs and this is something that I am going to try out in my 3rd-year Quantum Mechanics course this fall.

It turns out that for intro physics there is an option which will save me this work. I am using smartPhysics this year (disclaimer: the publisher is providing the text and online access completely free to my students for the purposes of evaluation). To explain what smartPhysics is, I will pseudo-quote from something I previously wrote:

For those teaching intro physics that are more interested in screencasting/pre-class multimedia video presentations instead of pre-class reading assignments, you might wish to take a look at SmartPhysics. It’s a package developed by the PER group at UIUC that consists of online homework, online pre-class multimedia presentations and a shorter than usual textbook (read: cheaper than usual) because there are no end-of-chapter questions in the book, and the book’s presentation is geared more toward being a student reference since the multi-media presentations take care of the the “first time encountering a topic” level of exposition. My understanding is that they paid great attention to Mayer’s research on minimizing cognitive load during multimedia presentations. I will be using SmartPhysics for my first time this coming fall and will certainly write a post about my experience once I’m up and running.

Since writing that I have realized that the text from the textbook is more or less the transcript of the multimedia presentations so in a way this textbook actually is a reference for the pro and an introduction for the novice. They get into more challenging applications of concepts in their interactive examples which are part of the online homework assignments. For example, they don’t even mention objects landing at a different height than the launch height in the projectile motion portion of the textbook, but have an interactive example to look at this extension of projectile motion.

The thing with smartPhysics is that their checkpoint assignments are basically the same as the pre-class assignments I have been using so it should be a pretty seamless transition for me from that perspective. I still haven’t figured out how easy it is to give students direct feedback on their checkpoint assignment questions in smartPhysics, and remember that I consider that to be an important part of the student buy-in that I have managed to generate in the past.

(edit: the following discussion regarding reflective writing was added Aug 11) Another option for getting students to read the text before coming to class is reflective writing, which is promoted in Physics by Calvin Kalman (Concordia).  From “Enhancing Students’ Conceptual Understanding by Engaging Science Text with Reflective Writing as a Hermeneutical Circle“, CS Kalman, Science & Education, 2010:

For each section of the textbook that a student reads, they are supposed to first read the extract very carefully trying to zero in on what they don‘t understand, and all points that they would like to be clarified during the class using underlining, highlighting and/or summarizing the textual extract. They are then told to freewrite on the extract. “Write about what it means.” Try and find out exactly what you don‘t know, and try to understand through your writing the material you don‘t know.

This writing itself is not marked since the students are doing the writing for the purposes of their own understanding. But this writing can be marked for being complete.

Clicker questions and other (inter)active physics classroom resources

Chad doesn’t mention anywhere in his post that he is thinking of using clickers, but I highly recommend using them or a suitable low-tech substitute for promoting an (inter)active class.  I use a modified version of Mazur’s Peer Instruction and have blogged about my specific use of clickers in my class in the past. Many folks have implemented vanilla or modified peer instruction with cards and had great success.

Clicker question resources: My two favourite resources for intro physics clicker questions are:

I quite like the questions that Mazur includes in his book but find that they are too challenging for my students without appropriate scaffolding in the form of intermediate clicker questions which can be found in both the resources I list above.

Clicker-based examples: Chad expressed frustration that “when I do an example on the board, then ask them to do a similar problem themselves, they doodle aimlessly and say they don’t have any idea what to do.” To deal with this very issue, I have a continuum that I call clicker-based examples and will discuss the two most extreme cases that I use, but you can mash them together to produce anything in between:

  • The easier-for-students case is that, when doing an example or derivation, I do most of the work but get THEM to make the important mental jumps. For a typical example, I will identify 2-4 points in the example that would cause them some grief if they tried to do the example completely on their own. When I work this example at the board (or on my tablet) I will work through the example as usual, but when I get to one of the “grief” points I will pose a clicker question. These clicker questions might be things like “which free-body diagram is correct?”, “which of the following terms cancel?” or “which reasoning allowed me to go from step 3 to step 4?”
  • The other end of the spectrum is that I give them a harder question and still identify the “grief” points. But I instead get them to do all the work in small groups on whiteboards. I then help them through the question by posing the clicker questions at the appropriate times as they work through the problems. Sometimes I put all the clicker questions up at the beginning so they have an idea of the roadmap of working through the problem.

An excellent resource for questions to use in this way is Randy Knight’s 5 Easy Lessons, which is a supercharged instructor’s guide to his calculus-based intro book. The first time I used a lot of these questions I found that the students often threw their hands up in the air in confusion. So I would wander around the room (36 students) and note the points at which the students were stuck and generate on-the-fly clicker questions. The next year I was able to take advantage of those questions I had generated the previous year and then had all the “grief” points mapped out and the clicker questions prepared for my clicker-based examples.

Group Quizzes

Not related to clicker questions, but they are related to the (inter)active class: group quizzes are something that I have previously posted about and I have also presented a poster on the topic. I give the students a weekly quiz that they write individually first, and then after they have all been handed in they re-write the quiz in groups. Check out the post that I linked to if you want to learn more about exactly how I implement these as well as the pros and cons. Know that they are my single favourite thing that happens in my class due to it being the most animated I get to see the students being while discussing the application of physics concepts. It is loud and wonderful and I am trying to figure out how to show that there is a quantifiable learning benefit.


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