Even after a previous physics course with a fantastic focus on conceptual understanding of circuits, my AP Physics 2 students still struggle when reasoning through some scenarios. Today, I posed the following question:
Students agreed that bulb A would again be brighter. They were also able to justify their answer by stating that the current through the bulbs is the same and the resistance of the bulbs is different. What threw them was when I asked which bulb had the greater resistance.
I wanted to do a resistance paradigm lab to start the circuits unit in AP Physics 2. I found a Nature of Resistance series of activities from ￼￼the CLASSE Institute for Physics Teachers. The activities seemed well designed and emphasized the connections between macroscopic observations and atomic interactions. Today, after an introduction with an incandescent light bulb and the standard Modeling Instruction paradigm lab discussion, students focused on graphically and mathematically modeling the relationship between resistance and either length or cross-sectional area of the Play-Doh resistor. The accuracy of the data wasn’t fantastic, but they had a lot of fun and saw the relationships among the variables.
I’ve been grading these big “Interim Assessment” tests for an eternity, and I’ve gotta say I’m impressed with the work some students did. We spent a lot longer on our qualitative energy unit than I’d intended, but it never felt stale. What we’ve ended up with is a pretty cool little language, spoken mostly through the energy bar charts. They allow us to say things that make real connections to what’s happening in a situation.
This example is a favorite of mine. We can see all kinds of variety in this example. Starting with evidence about speed, height, and shape, then inferring Ediss and perhaps Echem from there, we can see details about why a ball bounces higher when you throw it down, etc. Intuitive and not-so-intuitive predictions can be made by simply referring to a sketch of a bar chart.
This test was the first time we’d seen a squished rubber ball, and some students figured out that elastic energy must be stored in that squished ball. This student has envisioned energy dissipating as a continuous process that happens both before and after “Moment B”.
This is the same room as students who blindly guess at all bars because they haven’t made the connection that a dot next to an object means that Ek is zero…
##etm ##physicsfirst ##representations
I was out of the classroom today while the AP Physics 2 students completed the electrostatics unit exam. I dug through my photos and found one of a whiteboard from a few days ago that I didn’t use in that day’s post. It is an electrostatics conservation of energy problem. The group that prepared this whiteboard included an energy LOL diagram. I’m thrilled how that particular representation helps students organize their knowledge for conservation of energy problems. I can’t believe it took me so long to integrate them into my teaching!
College-Prep Physics: Today students designed their own labs using pull-back toy trucks. They formulated their own question, designed their own procedures, collected data, and analyzed it. The one stipulation was that both the independent and dependent variable must be quantifiable because they are developing a specific mathematical model for their data. Later they will be presenting their results on mini-posters and sharing with the class.
NGSS Science and Engineering Practices:
#1. Asking questions and defining problems
#2. Developing and using models
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking