Pedagogue Padawan 180

Today in AP Physics 2, we began to investigate the concept electrical potential energy. It is important that students have a strong understanding in electrical potential energy before we start to investigate the concept of electric potential. While students are familiar with other forms of potential energy (gravitational, elastic), a couple of aspects of electrical potential energy provides a challenge. One, unlike gravitational potential energy, the electrical potential energy depends not only on the position of the particle in the field but on the sign of the charge of the particle as well. Two, negative electrical potential energies are quite common. While “zero” gravitational potential energy could be defined such that negative gravitational potential energies are considered, students rarely encounter this in their first-year course.

Students spent most of class today, thinking through the following nine scenarios (from Knight’s Five Easy Lessons) and whether the electrical potential energy of the particle increases, decrease, or stays the same from the initial point to the final point; first individually, then among their groups, and finally as a whole class. It was fantastic to hear students justify their answers in terms of energy conservation, work done on the particle, and the relationship between the direction of displacement and force.

  ##electrostatics  

Based on the recommendation of a student, I showed the class this excellent video on fields produced by Minute Physics:

It introduces the concept of fields and the historical background of the discovery of that model, even introducing the concept of scalar and vector fields. I love the particles of cheesecake passing through space field! It also serves to introduce the class to Minute Physics if they are not already familiar. (Although I hope by now that they all are!)

Students completed a practice quiz on the concepts of electric forces and fields. I need to follow up with a handful of students who struggled on the quiz and ask if they are struggling to understand the concept of an electric field or if they didn’t carefully read one of the questions and thought they were to be solving for the electric force instead of field.

  ##electrostatics  

Today, we built upon the computational models for Coulomb’s Law which essentially became electric field vector diagrams. Historically, students have struggled to develop a deep understanding of electric fields. In the past, I used to “cover” electric fields in our first year course. I found that in AP Physics B, students retained little understanding. The past couple of years, I have introduced fields using the recommendations in Knight’s Five Easy Lessons; specifically, page 207-208. I’m impressed by how much discussion and learning can be achieve related to this simple diagram:

As recommended in the book, I ask students to draw the corresponding electric field vectors at each of the three points. I then point to the middle of one of the vectors and ask them if an electric field exists at that point and, if so, what is its direction. Finally, I ask them to draw force vectors for charges of different signs and magnitudes at the points. This sequence of questions seem to address many of the common misunderstandings regarding electric fields.

  ##electrostatics  

Today, we started class with students sharing their computational models. I then used one of the students models that attached a vector for the net force to the point charge to illustrate how their model showed the direction and relative magnitude of the electric force at every point through which the point charge moved. I then asked what we could do if we wanted to know the direction and relative magnitude of the electric force at every point around a charged object. Once they said that we would need a lot more point charges, I showed them this model:

While tomorrow’s lesson will formally introduce the concept of the electric field and its relationship to the electric force, I did use this model as a bridge by introducing the visual of electric field vectors. I also showed them another model with multiple charged objects to demonstrate that the electric field vectors represent a superposition of the electric force due to each charged particle:

I tried to write this model in a fairly extensible manner to make it easy to model various configurations of charged objects.

  ##electrostatics ##representations ##tech ##glowscript  

Today, AP Physics 2 students continued to develop their computational model of a the electric force on one or more point charges due to one of more charged objects. Some developed simple harmonic oscillators; others, helixes; others, eccentric orbits. Everyone got at least a basic version of the computational model working. Brandon, Tiffany, and Chris made some of my favorites:

  ##electrostatics ##representations ##tech ##glowscript  

Today, AP Physics 2 students started developing their a computational model for Coulomb’s Law. Unlike some of their previous computational models in GlowScript, I provided a minimal framework this time. The goal of students developing their own computational model for a free point charge in the presence of a fixed charged object was threefold: 1) students would develop a deeper understanding of Coulomb’s Law; 2) this model would serve as a bridge to understanding electric fields; 3) this model provides an opportunity to model a dynamics problem using vector math. In order to work towards this third goal, I introduced the concept of a unit vector and the functions to normalize a vector and returns its magnitude.

  ##electrostatics ##representations ##tech ##glowscript  

Today AP Physics 2 started the Electrostatics unit. The first topic was electron theory, which is review of last year’s class for all students (regardless of which class they took last year). Rather than a review lecture which would have little engagement, I finally had the idea to leverage peer instruction in this context. I presented a few notes on electron theory, emphasized the theme of explaining macroscopic phenomena from an atomic perspective, and then we spent the rest of class discussing conceptual questions via peer instruction. Students were much more engaged and I had much greater confidence in what they did and didn’t retain from last year.

  ##electrostatics ##peerinstruction  

Today AP Physics 2 concluded the thermodynamics unit with an exam. I didn’t bother to take a photo. Instead, I’ll share a photo from my 8th hour AP Computer Science class. They were having trouble focusing minutes before the bell and also discovered there were buttons on the monitors with which they could play.

Nice rainbow!

  ##thermo  

I felt that the AP Physics 2 student needed one more day practicing solving problems before the thermodynamics exam. I supplied a couple of practice problems and students worked together in small groups to solve them. They were very engaged. At the end of class, students were definitive that the practice was very helpful. We’ll see how tomorrow’s exam goes….

  ##thermo  

Today in AP Physics 2, we spent the entire period discussing conceptual questions via peer review. The past couple of times I felt that we didn’t explore that many questions after we finished the quiz. So, today we had all of class and went back and discussed some of those questions we didn’t have time for previously. My favorite was this Next-Time Question by Hewitt that highlights the difference between temperature and thermal energy.

I had students type their answer as a couple of sentences into InfuseLearning. It was helpful to share various answers as examples and highlight their strengths and weaknesses.

  ##thermo ##peerinstruction