Day 160: Color Coding for Electric Pressure

Today, we continued developing the electric pressure model. I introduced the CASTLE representation for electric pressure where the relative pressure is denoted by different colored wires in the circuit diagram. The contrast of colors reinforces that there must be an electric pressure difference in order for current to flow and bulbs to glow. In addition, if the current is constant, elements with greater resistance require a greater difference in electric pressure than elements with less resistance. This year, my colleague carefully chose the diagrams such that five colors of electric pressure (highest, high, normal, low, lowest) would suffice, which avoids having to color wires orangish-red. This diagrammatic technique is a powerful way for students to visualize voltage. For homework tonight, they will revisit the pizza problem and solve it using our new electric pressure model.


  ##circuits ##representations  

Day 159: The Air Capacitor

In Honors Physics, we have finished elaborating the current model, identified its limitation with the pizza problem, and have started exploring the voltage model. We are now using the CASTLE materials including the modifications for Modeling Instruction. Presenting voltage as the difference in electric pressure resonates well with students. The concept is reinforced by drawing an analogy to air pressure. I introduce this analogy with the air capacitor:


The air capacitor is constructed from two peanut butter jars with rubber stoppers and fired glass tubes in each end. A balloon is stretched around one of the jars and then the jars are joined with packing tape such that the balloon acts as a membrane between the two halves of the air capacitor. The balloon serves as a visual indication of the pressure difference between the two halves of the apparatus. This apparatus reinforces a couple key aspects of the analogy:

  • air moves from high pressure to normal pressure (blow into one half)
  • air moves from normal pressure to low pressure (suck out of one half)
  • in general, air moves when there is a difference in pressure
  • pressurized air is stored in the capacitor when it cannot flow elsewhere (plug the ends of the air capacitor)
  • the air that leaves one half of the air capacitor is not the same air that enters the other half; the air that leaves was already in the air capacitor

  ##circuits ##equipment  

Day 158: Freshman Jamboree

Every spring, the teams and clubs gather in the field house to welcome the incoming freshmen, show them the variety of activities available, and sign up potentially interested students. Huskie Robotics, FIRST Team 3061, and Physics Club were there in force. This year’s robot, Annie, drew a crowd and the students, as always, did a fantastic job sharing their passion for FIRST and the team. Sixty five incoming freshman expressed interested and signed up. This year we gathered their personal email addresses so we can invite them to summer events.


  ##local ##omgrobots ##makeitloud  

Day 157: Mastery Manager

I’ve used a few assessment tools over the years. I still have nightmares about some. Due to these emotional scars, I’ve been putting off trying our district’s latest tool, Master Manager. Both my AP Computer Science and AP Physics classes are in the midst of their final exams (which double as practice for their AP exams); so, I decided to see if Mastery Manager could help in the administration and analysis. I’ve been really impressed so far. Every time I went looking for a feature, I found it. I can score an assessment based on multiple sections, print forms based on a different set of sections, capture both multiple choice and free response scores, generate efficient student reports, and see all the item analysis statistics.

Screen Shot 2014-04-26 at 10.40.19 PM


Day 155: NGSS Performance Standard Sequencing

Today while students took the PSAE (Prairie State Achievement Exam), those of us on the Science Curriculum Team continued to analyze the Next Generation Science Standards (NGSS) Performance Expectations, organize them into cohesive groupings, and sequence them into courses for 6th through 11th grade. By lunch, we had an example from each of the eight groups prepared for our gallery walk.


There were several different approaches. Some, like my group’s, were more traditional than others, though we did incorporate the idea of end-of-term capstones. One group had a particularly attractive freshman course. It had a wonderful narrative rather than just being a collection of related units. It would be challenging to teach that course and maximize its potential as it would require teachers of a certain mindset, familiarity with a variety of disciplines, confidence, and flexibility.

We continue our work tomorrow and it will be interesting what elements of these ideas the team converges towards by the end of the day.


Day 154: Create Your Own Critter

Today, my AP Computer Science students began their final exam. While they were working through the multiple choice, I was reviewing their Create Your Own Critter lab and providing feedback. The lab is the summative lab for the GridWorld Case Study unit and has the following requirements:

Create your own critter which inherits from Critter. Be creative and think of some other things your critter can do that we haven’t done. You need to:

  • find a small gif file that looks like your critter – approximately 48×48 pixels and put it in your folder with your source file (must name it the same as your class)
  • have the new critter move differently from a Critter and/or
  • have the new critter eat or leave different things that the Critter doesn’t do and/or
  • have the critter do other things
  • your critter must override at least three of the five methods in the act method or you must have 2 classes (critter with another critter or actor) where there is at least two overridden methods in each. Do not override the act method.
  • add comments in your code (JavaDoc-style)
  • type up a full description of your Critter(s) in the README.txt file that is part of your BlueJ project and make sure it is submitted in your zipped project folder; the description should completely describe the behavior of your critter
  • write a runner class to demonstrate your critter and its behavior
  • submit a single zip file that contains the BlueJ project folder with the BlueJ package file and all source files

I love it when students go well beyond the requirements and create something amazing that is either really creative or challenges them. One student incorporated a shortest path finding algorithm into her lab!

  ##gridworld ##apcs  

Day 153: Circuit Whiteboards

After about a week of investigating circuits and the current model, we checked our understanding by presenting whiteboards of a series of problems. The discussion was okay and any mistakes were quickly identified. We do a lot of ranking problems followed by a discussion to justify the rankings. At this point, students only have the current model with which to apply, so several of these problems are more challenging than they would be if the voltage model was applied.


  ##whiteboarding ##circuits  

Day 152: A New Approach to Circuits

This year in Honors Physics (a.k.a. AP Physics 1), we are using a combination of the Physics by Inquiry materials and the Modeling Instruction CASTLE materials. Our current model is based on the Physics by Inquiry investigations and the electric pressure (voltage) model is based on the Modeling Instruction CASTLE materials. I’m thoroughly enjoying the investigations that we are doing. Groups are engaged in careful observation and the construction of long chains of reasoning. I have the opportunity each class period to visit every group and have an in-depth discussion with each about their observations and conclusions. I ask each small group the necessary questions to expose their inconsistencies in their analysis and refine the model that they are constructing. Today, most groups analyzed the “pizza problem:”

Screen Shot 2014-04-18 at 9.07.40 PM

In this exercise, students are asked to predict the brightness of bulb A and B when bulb C is removed. Unfortunately, most groups made predictions and then built the circuit to check their predictions. Their prediction for bulb A was correct, but most groups simply accepted that their prediction for bulb B was either right or wrong and didn’t carefully consider why. I had to ask several questions before these groups realized that they didn’t have a good explanation for why bulb B should be brighter or dimmer, and that was the point of the exercise – to expose the limitation of our current model. This is also why the circuit is called the pizza problem: “What is greater? Half of a large pizza or all of a small?”

Next year, I will explicitly instruct students not to build the circuit for this exercise, but instead throughly defend their prediction to each other and me. I think they will more easily recognize the limitation of the model when they can’t simply observe that bulb B is brighter in the actual circuit.

  ##circuits ##paradigmlab ##setbacks  

Day 151: Deriving the Algorithm for Fractal Trees

In AP Computer Science, we are finishing our last unit before the AP exam. The summative lab is the Fractal Tree Lab. This year, students are provided much less direction. However, today, I did offer to work through the derivation of the algorithm with those students, who after working on it for most of day, wanted some assistance. They really just needed some help enumerating the key parameters for the recursive method and the geometry necessary to derive them. Here’s what we came up with:


I think the key idea is that the angle of the previous branch relative to the coordinate system needs to be passed as a parameter. This facilitates the calculation for the endpoints of the new branch. I’m excited to see if this year’s class is as creative as last year’s given that they have to struggle much more to derive the basic recursive algorithm.