Day 111, 114, and 115: In Recovery Mode

Wednesday, March 28. Monday, April 2. Tuesday, April 3.

I was doing so well posting nearly every day, and then Robotics happened. I’m still recovering. I don’t remember at all what I did last Wednesday. Drat. Thursday and Friday I had a substitute while I was robotics-ing. Returned Saturday night and promptly got sick. Feeling tired, run-down, and sore-throaty. I’m zero surprised at the first two, but rather irritated at the last one. My voice sounds like I smoke 50 packs a day when/if it is actually working instead of cutting out entirely. Not conducive to the teaching of the physics. I do my best.

Physics: Monday we talked about electric current and answered the many, many questions students had from the textbook reading that is nearly incomprehensible. I get so annoyed at textbooks that try to introduce circuit elements and properties of circuit elements before circuits. Talking about the properties of capacitors is pointless and contextless if you aren’t talking about what it DOES in a circuit. Asking students to understand the conversion from AC to DC using a capacitor and diode might as well be talking about the conversion from BL to EA using a winger and a plobbit. Being able to repeat vocabulary in no way demonstrates understanding. Whatever. I’m cranky. Tuesday we introduced circuits and had them use the Circuit Construction Kit from PhET to explore series and parallel structures.

Honors Physics: Monday we talked more about induction and practiced right-hand rules. I have a specific way I have the students approach induction problems that I think simplifies it considerably. There are four questions to ask yourself when solving an induction problem:

  1. What was direction of the original magnetic field?
  2. How is it changing? (increasing or decreasing)
  3. What is the direction of the responding induced field using Lenz’s Law? (If increasing, induced field is in the opposite direction. If decreasing, induced field is in the same direction as #1)
  4. Based on the answer to #3, use the right-hand rule to discover the direction of the current that creates the field in the required direction.

Here’s an example with a table for them to use when answering these questions.

Screen Shot 2018-04-04 at 8.37.02 AM

And here is the filled out table with the answers. Because some students have trouble with spacial reasoning, I made the loop so that the front side was solid and back was dotted and then they had to tell me the direction of the current on the front of the loop to help with the clockwise/ccw confusion of which direction you’re looking at the loop changing the relative direction of the current.


This is the best tool I have found for getting students to ask themselves the right questions in the right order. I’ve been meaning to make similar structures for other types of problems, but it just hasn’t happened yet, just like the four billion other resources I intend to make “at some point”.

AP Physics: Monday and Tuesday was finishing up the course! We’re done with new content! DONE DONE DONE DONE DONE! Monday we did LR circuits, then Tuesday we did LC circuits and Maxwell’s equations as a wrap up. For the LC circuits I began with a review of spring/mass systems, which confused the hell out of the students. I had to keep reassuring them that there was a reason for this, to hang in there with me, it will all make sense in ten minutes. The sweet class was right there with me the whole time. The judgy class was far, far less willing to roll with it, but eventually came around.

We hadn’t done spring/mass systems with DEs, but since the spring/mass system and the LC circuit have the exact same mathematical behavior (FRICKIN’ WEIRD, y’all), I wanted to backtrack and do the confusing math on something familiar before we jumped into something completely new. It ended up working very, very well. Once we started analyzing the LC circuit, they were right there with me whole time. Well, we had some lengthy discussions about the signs of the potential change across the inductor and the capacitor, which I got through best I could, but I’m not sure it made sense to everyone. I need to work on clearing that understanding up a bit. But! Once we got that sorted, the rest of the analysis was a snap and everything went smoothly.

Then we watched two videos on Maxwell’s Equations (Dan Fullerton and Crash Course). And that wraps the class! Woooooo! From here on out is review, a midterm on Friday, and then going all the way back to Kinematics as we begin Mechanics review next week. Pazow, AP Physics C! YOU’RE FINISHED!


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