Igloos and big sweaters: Pre-class overheads (October 28 – November 1)

(This post is part of an ongoing, semester long series. Each week, as a lecture TA in Physics 100, I choose a pre-class overhead for each of the two lectures I help out in. I attempt to choose images that connect to the current material and that are fun and possibly provocative. Here, I keep a record of the images I choose and thoughts I have about the in-class outcomes.)

2048px-Iglu_1999-04-02Moving on from power, we began working on thermal conduction in Physics 100. The main example worked through in the lectures was computing the power of a space heater needed to keep a cabin heated. Along these lines, the first pre-class overhead I chose for this week was a picture of an igloo. We put up this image with no prompting phrase and the instructor did not try to initiate a conversation this time. Rather, he explained it in the context of heat conduction as a lead-in to the lecture.

Although I thought the connection to thermal conduction was clear, a conversation with a student revealed that this may not have been obvious. During the pre-lecture time, I asked a student about the pre-class images in general and whether or not they thought they were a good contribution to the class. The student agreed that they were a good contribution and went on to muse about the igloo. Interestingly, the focus of their musing was on the structure of the igloo and not on how it might keep the inhabitants warm in such a cold atmosphere. Now, I’m happy that the igloo picture got the student to think something! (Especially a physicsy question about how the igloo was able to stay up.)  However, I was surprised to hear something different than thermal conduction physics. Upon reflecting, I realize that the structure of the igloo never even crossed my mind because I went searching for a picture directly after reading through the thermal conduction lecture (and after thinking through the cabin heat loss worksheet). I was stuck in a ‘thermal conduction frame of mind’ and did not appreciate that there could be alternative interest points and interpretations. This conversation was a good reminder that students may (and likely usually do) see things differently than the instructor or the TA.

I wonder how the environment affected the student’s thoughts and how their thoughts influenced their behaviour in the lecture. For example, did being there for a physics class cause them to think of something physics related (the structure)? Was having a physics-related thought enough to put them in a good frame of mind for the rest of the lecture or was it not useful because they did not make the explicit connection to the current material?

For the second lecture of the week, I chose this picture of a happy lady in a large purple sweater. I put it up in the pre-lecture with the queuing phrase, “Why is she so happy?”. The instructor attempted to initiate a discussion based on the image and phrase, but the class was having trouble settling down. (This extra rambunctiousness could have been because it was Halloween.) As a result, the instructor again ended up explaining the relevance of the image as a lead in to the lecture. Before and after the class, I did overhear some students commenting on the lady with the sweater. At the very least then, this image attracted some attention.

Comment/question starters

Some possible comment starters for you:

  • The student’s wondering about the igloo’s structure was useless because …
  • The student’s wondering about the igloo’s structure was useful because …
  • The student would never have thought about the structure if you showed them the igloo while they were at …
  • Some interesting heat conduction related images I would have considered are …
  • A good queuing phrase for the igloo would be …
  • A better queuing phrase for the lady in the sweater would have been …
  • A way you can use pre-class overheads more effectively could be ….
  • What is your goal with the pre-class overheads?
  • The main goal of pre-class overheads should be _____________. To accomplish this, you should …

(Igloo attribution: By Ansgar Walk (photo taken by Ansgar Walk) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC-BY-2.5 (http://creativecommons.org/licenses/by/2.5)%5D, via Wikimedia Commons.)



  1. Andy "SuperFly" Rundquist · · Reply

    I think this is a cool image to use for this topic. My boys are always interested to see how warm they can be in our snow forts (it’s usually what we make after digging out from big storms). I like this idea of having pics up to spur conversation. I’m trying to seed those conversations by emailing my class a “question of the day” like “what makes noise when you snap?” and sometimes we have a fun conversation about it in class. However, much like the conversation you describe, sometimes the students focus on aspects of the question that I wasn’t planning on. I find that I’m not always very good at going with their passion in those instances.

    If you were running the class, what would you have done if someone had piped up about the structure?

  2. Hi Andy, good question! It made me think about the scenario for a bit – a good exercise in case I am at the front of the class at some point in the future.

    When, in our one-on-one conversation, the student mentioned the structure, I agreed that it was interesting in that aspect, and I did not push the thermal conductivity perspective on them. I think that if I hope that these pre-class overheads help students bring prior knowledge into the classroom, you need to support and encourage their ideas, even if they are outside of the lines you are thinking. After all, if you shoot them down, or imply that your interpretation is the correct one, I think they’d be less likely to volunteer their opinion the next time.

    If I were running the class, I hope my response would have been similar. Ideally, I would thank the student and acknowledge their contribution, then move on to solicit more ideas. If other students picked up on the structure idea, perhaps you let them go with it for a bit, even if they never get back to the idea you were hoping them to pick up. After all, I think that, in this context (a large-scale first-year course for students that will not be physicists), empowering them to contribute to class may be more important than them nailing the precise connection you had in mind. Maybe it is even a detriment to use a prompting image that has too obvious a connection to the material, if your goal is to promote contributions.

    Would you agree with this strategy in this context? How about in the context of your classroom?

    1. Andy "SuperFly" Rundquist · · Reply

      That seems like a great approach. I would like to think that I’m willing to follow my students’ passions, but I know I put too much pressure on myself to follow the syllabus. Making an environment where they feel like it’s ok to ask questions seems to be super important, and I hope that I can get better at that.

      How do you think they would have responded to this:
      Student: the structure is the key . . .
      you: others?
      Others: yeah, I agree.
      you: what about the structure
      someone: well, the arch . . .
      you: what if the material were different, would the structure still be optimized?
      others: maybe
      you: what about the thickness of the walls?

      and then you’re off to where you wanted to be.

      1. @Andy – That’s some nice agile teaching! I imagine that if you used pre-class overheads often, you would become much more proficient at gently guiding the discussion to where you wanted it to be. With that you would probably be just as excited to hear a “physics you didn’t expect” observation as opposed to the one you were looking for.

        @Jared – Being new to large lecture-hall courses I hope that I am able to promote contributions the way that you have also said you would hope to do if you were running the course. I think you may have stumbled onto a topic to study, which is how does the obviousness of the connection contribute to the amount of or quality of the contributions from the students.

      2. @Andy: That sounds great for that situation! However, I know that sometimes it can be tough to come up with something as clever as that on the fly and in front of the class. Perhaps with some thought and practice, like Joss said, it could go much smoother. That will certainly be something I plan to consciously work on if I end up an instructor.

        @Joss: Thanks for the credit for my hypothetical classroom discussion moderation! That question sounds like it could be interesting… Perhaps we could define obviousness of the connection using expert opinions, and it would be easy to count the number of comments. We should discuss this more!

  3. I’ll bite the bullet and leave a comment centered on what I would consider the main goal of pre-class overheads should be. In the case of thermal conductivity, igloos are certainly an interesting example that the class has knowledge of, thereby connecting them with the material. Although, how many people in the class – heck, at UBC as a whole – have actually been in/had direct experience with an igloo? Likely not many.

    I’m leaning towards the idea of establishing a a more personal connection – an example that has actually affected them at some point in their lives. Granted, I don’t know what that would be in the case of thermal conductivity, but it might help establish a stronger association with “why should I care?”

    1. Thanks for the comment Chad! For thermal conductivity, how about a drink koozie? Surely more people in the class would have seen/used on of those.

      An advantage of an example like the koozie might be that the instructor could start by making an easy connection to the class, with something like, “Who has used one of these before?” Once people raise their hand, you could go on to, “Why did you use it?”. You could even directly address someone that raised their hand.

      But, I can also see merit in an extreme example like an igloo. I’ve never been in or had direct experience with an igloo. But it’s a house made of snow! In a terribly cold environment! That makes it interesting for me. I’m not sure if students respond better to this more novel thing or to the common thing (the koozie).

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