Wednesday, July 18, 2018

Be careful with your parabolic mirror


Let's say you you were into making solar ovens. Let's say that you decided a few years ago to make the best solar oven ever. Further, let's stipulate that you saw a nearly meter-diameter Direct TV antenna on the side of the road. An idea happened. You rushed to the local plastics store and bought highly reflective Mylar and glued it to the antenna.

Your solar oven was pretty amazing. While the hot spot wasn't super small, it was hot. Really hot. It can pasteurize a liter of water in 15 minutes.

And now you work at the Exploratorium and you think that you might bring it to work for grins. If you forget it in the back of the your Outback face up on a sunny day near the solstice, well, it can melt the molding in a fairly impressive way. I think I was lucky that my car didn't catch on fire.



You might be wondering how I could make such a mistake? I had a lot to carry into the Exploratorium, and the mirror wouldn't fit on the cart. I planned on coming back in a few minutes, but I got busy doing something else, and it slipped my mind. Coming back in the afternoon, I sat in the driver seat and looked into the rear view mirror.

Uh oh.



If you want to make your own parabolic mirror, you can find some excellent instructions here.

Marc "Zeke" Kossover

Sunday, July 08, 2018

It's Not Easy Explaining Green

I had heard that when an LED is submerged in liquid nitrogen (LN2) it changes color. After the PTSOS workshop last January I had some leftover LN2 and decided to see for myself. I replaced the incandescent bulb in a Mini-Maglight with a green LED and submerged it in a Dewar of LN2. This was the result:


I was pleased when the color change was very apparent as the audio track confirms. My expectation was that the green light would change to a lower energy wavelength like yellow. I had a little familiarity with how LEDs work and knew the energy of the emitted photons was based on the band gap energy. I thought a colder material would have a lower band gap energy. My observation confirmed what I would find out later to be an erroneous expectation. Fortunately, after I made the video I got out my Red Tide spectrometer and recorded the spectrum of the LED at room temperature (22 degrees C) and in LN2 (-196 degrees C). I took a quick look but didn't study it because it was a Friday and I had spent enough time fooling around, er, I mean experimenting, in my class room. I tweeted out the video and went home.

Still image of original Tweet, link to entire thread below

The next day the tweet was getting a lot of attention. Several people responded that the color should blue shift when submerged in LN2. Others sent me related links and I started reading up on the subject. These confirmed that the band gap energy should increase as the temperature decreases although one source indicated that it could go the other way for some materials. Most of these sources invoked quantum mechanics in their explanations, much of it went over my head. After reading many sources I found an explanation that would satisfy a high school student (or teacher!). But first they would need to understand how p-n junctions and LEDs work. If you want to wade through all the replies to my tweet, here is the link:
https://twitter.com/kilroi22/status/962145895805476864
https://twitter.com/kilroi22/status/962145895805476864
p-n junction diagram from TheNoise at English Wikipedia

A p-n junction is a piece of semiconductor divided into two regions. The p-type side (p for positive) has impurities added that cause the semiconductor to accept electrons. The n-type side (n for negative) impurities cause the semiconductor to give up electrons. At the junction between the two materials, the electrons from the n-type side are attracted by the p-type side and drift into it. This leaves the region on the n-type of the junction side lacking electrons and the region on the p-type side with extra electrons. A region lacking electrons can be described as having positive "holes" (see diagram above). Now the remaining electrons on the n-type side face a potential barrier from the electrons on the other side of the junction. An applied voltage can get them to flow to the p-type side if it is large enough to overcome the potential of the barrier. The energy required for an electron to overcome the potential is the "band gap energy". An LED is a semiconductor with a p-n junction. If enough voltage is applied to the LED, the electrons receive enough energy to cross the junction, then drop back down in energy, giving off light. This is analogous to an electron being excited to a higher energy level in an atom, then dropping back down, giving off a photon of light having a very specific energy or wavelength. An LED differs because there is a spread of possible photon energies that can be emitted, centered on what is most probable, the band gap energy. The color or wavelength of an LED is often, but as we will see, not always the same as the wavelength corresponding to the bang gap energy. The figure below shows the spectrum for a green LED at room temperature. The peak wavelength is 571 nanometers (nm). This is right on the boundary between what is perceived by the human eye as green or yellow. The overall green color that is seen is a result of all the photons coming from the LED. Since the human eye peaks in color sensitivity at about 555 nm, the green photons to the left of the peak have more of an effect on what is seen than those on the right.

Spectrum of green LED at room temperature using Ocean Optic's Red Tide Spectrometer

I naively thought that cooling down the LED would "shrink" the band gap energy, causing the most probable wavelength to be of lower energy. This would mean it shifts to toward the red end of the spectrum. When I saw the color change from green to yellow, it confirmed my expectation. After doing some research, I learned that my expectation was wrong and there should be a blue shift. This is because at lower temperatures, the electrons on the n-type side have a lower initial energy from the random thermal motion in the material. This makes it harder for them to overcome the band gap energy much like it is harder to jump over a ditch while standing still versus taking a running start. My video seemed to refute this explanation so I took a closer look at the spectrum of the LED at room temperature and in the LN2. (see figure below) The peak wavelength in LN2 did show a tiny blue shift. It went from 571 nm to 568 nm. The Red Tide spectrometer has a 1 nm resolution but I would say this essentially unchanged. The main difference between the two is the narrowing of LN2 spectrum. The room temperature spectrum has a larger fraction of green photons coming from it. The LN2 spectrum is depleted of the green photons, allowing yellow to dominate. There also are what appear to be some nitrogen absorption features in the LN2 spectrum.

Spectrum of green LED at room temperature and in LN2

I now had a new question, why does the spectrum narrow? The temperature change also affects the number of photons emitted. Being submerged in LN2 selectively suppresses emission of green photons over yellow. Why this occurs I am not sure but it is definitely happening. This experience left me with other questions. What happens with other color LEDs? Will an infrared LED blue shift enough to become visible? Is the amount of blue shift dependent on the energy band gap? What would happen to a laser in LN2? When can I get some more LN2 and have a chance to try this? My chance came during the Fusion/Astrophysics Teacher Research Academy workshops I conduct at Lawrence Livermore National Laboratory. At the end of the first day we had some extra time and I brought out a Dewar of LN2 and we proceeded to immerse various light sources in it. The red laser pointer did not appear to change color but it eventually stopped working. It did recover after warming back up. An infrared LED appeared to show a very dim red light but it was hard to tell through the bubbling LN2. The ICE LED strip that contained blue, green, yellow, orange, red, and infrared LEDs was more impressive. It survived a lengthy immersion allowing us to see the blue dim but stay the same color, the green turn to yellow, both the yellow and orange turn to green, the red get slightly red-orange, and no sign from the infrared. None of the video turned out well and the teachers gathered closely around the Dewar made measurements difficult. I saved some LN2 to try again later by myself.

I finally got a chance the week after the LLNL workshops ended. I used ring stands and clamps so I could immerse the LED strip and record video hands-free. This allowed me to carefully measure the spectra. Below is the video in three parts, the initial immersion, after the LED strip reached equilibrium, and a sped-up video of the LED strip warming back up after removing it.


Frame grabs from video showing LED at room temperature and submerged in LN2

The video shows the same color changes that we observed in the workshop. No sign of visible emission from the infrared LED was seen. The infrared blocking filter on my iPhone prevented any infrared emission from showing on the video. The infrared emission does show on the spectrum as seen below. It shows a blue shift when immersed in LN2. The peak emission shifted from 934 nm to 904 nm. It would need to shift to at least 750 nm to be visible to the human eye. Some infrared LEDs peak at 850 nm. It is possible that they would shift enough to be visible but I doubt it.

Spectrum of infrared LED at room temperature and in LN2
The blue LED also shows a blue shift of the peak emission from 445 nm to 422 nm. However, this is due to a change in the relative intensity of the two peaks in each spectrum as shown in the figure below. The room temperature spectrum has a peak wavelength of 445 nm but shows a secondary peak at 425. The LN2 peak is at 422 nm with a secondary at 445 nm. I think the relative change in peak intensity has a similar cause as the green LED appearing yellow. The lower temperature is suppressing emission of certain energy photons more than others. Note: The intensity values on the y-axis of the spectrum graphs are not relevant because they depend mostly on how I aligned the fiber optic cable collecting the light. The blue LED dimmed noticeably so its intensity should be lower if everything else was equal. The small peak at about 570 nm is coming from the green LED that is adjacent the blue.

Spectrum of blue LED at room temperature and in LN2
The remaining 4 spectra are shown below. They all show a significant blue shift as they should according to the references I consulted. This green spectrum is very similar to the one I showed and discussed earlier. They both show a very slight blue shift and a depletion of emission of green photons. The small peaks on the sides are from adjacent LEDs on the strip.

Spectrum of green LED at room temperature and in LN2
Spectrum of yellow LED at room temperature and in LN2
Spectrum of orange LED at room temperature and in LN2
Spectrum of red LED at room temperature and in LN2

The red LED spectrum confirms the slight change from red to red-orange that was visible to the eye and in the video. Below is a data table of the wavelengths of the peak emissions as measured by the Red Tide spectrometer and Logger Pro software.



Notice the peak wavelengths for the yellow and orange LEDs are almost the same for both room temperature and in LN2. This is evidence that the color seen by the eye is more dependent on the overall emission from the LED than on the peak. The yellow LED at room temperature is not as narrow as the orange LED but has a little bit more emission from the yellow and green where the human eye is more sensitive. In LN2 their spectra and are almost identical and their visual appearance is almost the same green color.

If you are curious about the effect of temperature on LEDs, I have copied my references below. If you know or learn something relevant to this topic, please leave it as a comment. I am sure the next time I get some LN2 I will have a list of new things to try.

https://ecee.colorado.edu/~bart/book/eband5.htm

https://wiki.brown.edu/confluence/display/PhysicsLabs/7A30.10+LED+in+Liquid+Nitrogen

https://physics.stackexchange.com/questions/80513/how-does-temperature-affect-a-semiconductor-band-gap

https://www.researchgate.net/post/How_are_the_wavelength_of_LEDs_dependent_on_temperature

https://www.reddit.com/r/askscience/comments/2qxazo/why_does_led_glow_brighter_in_liquid_nitrogen_but/

https://io9.gizmodo.com/watch-an-led-light-change-color-in-liquid-nitrogen-1574982405

https://rebrn.com/re/changing-the-color-of-an-led-by-changing-simply-cooling-it-in-li-2844214/

http://www.circuitstoday.com/understanding-the-pn-junction

https://www.osapublishing.org/josk/abstract.cfm?uri=josk-19-3-311

Tuesday, July 03, 2018

Cell Phone Airbag Challenge

Videos and pictures of this airbag device have been circling the web the last few days:

While not available for production yet it is getting a lot of publicity, and rightly so. It is an ingenious design that appears to be effective and reusable. It got me thinking about Dan Burns and my Crash Cushion project. Students are asked to design a crash cushion for either a smart cart or a cart with an accelerometer on it to crash into. They are challenged to decrease the impact force as much as possible, something we hope they realize is accomplished by increasing the impact time. 

I want to assign this as an emergency sub assignment for students that can be done theoretically, no cracked screens needed. So I looked to see what other designs might already be out there and found this 2013 parody by Honda:

It is in Japanese and does not have subtitles but the engineering process is still evident in the parody video. The end product is a giant case for your phone which of course makes the phone impractical. I see the Honda version as where my students my start in the process and then the new spring loaded German design as where they might end, with lots of R&D in between.

I plan to start the activity by asking students what is necessary for an automatically deployed air bag for a dropped cell phone. They could work in pairs or groups and discuss the basics of the design criteria for a device that protects the dropped phone from breaking. I expect students to think about drop proof cases they may have seen commercially available that have enforced corners. Once they have made a list of the design needs groups/ pairs could share their individual lists to come up with a whole class list.

After their criteria has been established I would like to show students the original Honda parody video above. The original Honda video has been removed from their YouTube channel but the video is available on a few news sites. Since I can't find one with subtitles I'm not 100% sure its clean for the classroom but its probably safe since it was originally published on the official Honda page. Even on silent students can watch the video and observe his design process; it could be considered an advantage that they have to rely on the visual only and can't regurgitate anything they hear the engineer say. They will probably laugh at the final design but it will serve as a starting point for the next stage.

Before watching the video, or after, students can be given the shorter article about the parody video  that summarizes it and includes stills from the video. Ask students to discuss if the Honda Case N meets all aspects of their design criteria. If their class list was missing something about the phone case being of a practical size they will probably want to add it now. This should lead to a discuss about additional criteria they might want to add.

At this point you can ask students to actually start brainstorming an air bag device on paper. This may include some conjecture and may not hold up to questioning:
"There will be this bag that shoots out here..."
         "How will it shoot out?"
"Ummmm some kind of compressed gas..."
         "Where will that come from?"
"Uhhhh..."

And to an extent that is completely okay. Students aren't going to be able to build a workable model like they do with the Crash Cushions project. This activity is not even necessarily focused on the ideas of impulse either but more on reasonable design criteria

I found this article about the spring loaded German design and made a pdf to share with students. The original video can be shared as well, although it is in German. I plan to ask students what is most important to that design and if it meets all of their design criteria. Students can discuss differences in their design and the German spring loaded design, which of their own design criteria it does not meet, etc.

The viral German spring loaded design is expected to go to Kickstarter soon to crowd fund enough capital to begin production. You could continue the activity with students by asking them which of their own designs they would help crowd fund (before showing them the German design). After they see the German spring loaded design you could ask students if they support it enough to fund it as well, hypothetically of course.

While I plan for this to be a substitute activity it does require the sub to be capable of playing online video clips if your students do not have one-to-one devices like Chromebooks. My subs are not usually capable of operating my projector nor are we a one-to-one school so I don't know how likely I will be to implement this in the next school year. I've summarized everything, including questions I would ask students in this teacher guide for the activity.

I would love to hear any one else's ideas for extending this activity below. 

Friday, June 29, 2018

PhysX-Games

Throughout the year I mentally categorized everything as either pre- or post-AP. When I finally made it to the promised land of post-AP testing I then encountered a new challenge, keeping students engaged for a few weeks when they want to do absolutely nothing. I had many options, even putting a poll to them just for information (reserving the right to completely disregard their #1 choice of "do nothing"). I could talk about topics not covered in AP C like waves or optics or thermo or relativity? We could do a research project or have some kind of demo build? They could present a talk? Some ideas seemed better than others but the timing wouldn't work.

I finally settled on doing a series of group competitions, something different each day, something hands on and fun. I found lots of ideas online, some from labs I didn't get to do, but did struggle to find ones that were Electricity & Magnetism (second semester) focused instead of Mechanics (first semester) focused. I was hoping that the competitions could be on the same topics they would later be tested on for their end-of-semester final. Unlike most AP classes, I opted not to give students a final prior to the AP test. The argument is usually that students need the practice of an AP-like exam prior to the test; so we completed mock AP exams for practice but not for a grade. My students may take up to six AP classes in their junior or senior year so they have several weeks of high stakes testing (class finals) before more high stakes testing (AP exams). I decided that the practice and their mental health was more important than their grades at that point in time and they could take the final exam during finals week.

Since I was building the competition up from scratch there was a lot of writing, re-writing, last minute tweaking and of course post notes for next time. In the end it was a workable model with no major issues but as is often the case with the first time through, it wasn't quite right. In either case now I have examples and procedures for a series of activities to either use in the same way next year or throughout the year.

Day 1: Explanation and Bridge Building
On the first day I explained to them that they would be arranged into groups and competing each day for the rest of the school year. Each group was assigned a Greek letter and asked to come up with a clever name using the letter. I tried to split Chi, Psi, Pi, etc. from being in the same class and removed Alpha to save as my example of "The Alpha Academics." As expected, my students were way more clever than I and came up with some great names:
Gamma's Cookies
Oof (Omicron upper and lower case)
Beta Testers
Mooupsilon
Kappa-citor
An Iota of Understanding

I introduced the format of the competition using this powerpoint. It had the rules, grading specifics and the explanation for each day's competition, which was never revealed ahead of time. I explained to students that coming up with the name for our little competition was hard, I almost decided on the Phunger Games (like the Hunger Games series) but just couldn't. It came down to the morning of when brilliance struck and I decided to name it the PhysX-Games, complete with logo based on the popular X-Games:
Students were of course very concerned about how their grades would be affected by the competition. I did not wanted to punish them if their group didn't win every day but I wanted everyone to put effort in. I also wanted them to be rewarded for working well as a team and accomplishing tasks. I opted for a system that separated individual effort from group effort. Each day that students were present they could earn 5 points for actively participating. Each group would earn points for the day for accomplishing the task but they would earn more points for being the best at it. Good participation on an individual level required helping their group for the whole period. Sleeping, doing other homework or being caught with a cell phone meant zero points for the day. These participation points went into students' lab category so it was a welcome bump for most. If a student was caught with a cell phone that day their group could not win the competition, but it did not negatively affect the other group members' individual points. I would keep a running tally of each group throughout the competition so we could always see who was in the lead.

But why care if you are "winning"? The prize had been another sticking point initially. What do I offer students who are only a few weeks from graduating, that are mentally "done" after AP testing? I hadn't offered extra credit all year so it seemed like a good reward. Specifically I decided to add enough extra credit to their individual final exam grade so as to boost their semester grade by 1%. Yet with three classes of AP Physics C I had to find a way to limit my first few periods from giving the last class the "answer" to the challenges each day. I needed a way to keep groups between classes competitive. So I upped the reward. The group with the most points in each class would get points added to their final exam to raise their grade 1% but the group with the most points across all three classes would get 2% added to their grade. This was met with hoots and hollers in my classes. I need not worry about answers being shared between classes, they were in it for a grade bump and the competition was fierce.

After the explanation and group naming we didn't have time for a long competition on the first day. Instead we started with something basic, balancing uniform sticks over a table edge. Groups were given five uniform paint stirrers and five uniform meter sticks. They were given instructions which included the rubric I would be grading them on. Without attaching the sticks in anyway to the table or counter-weighting them students were to extend each group of five out as far past the table edge as possible. Points were awarded for balancing the sticks and a bonus was given to the group with the farthest reach for paint sticks and another for the farthest reach for meter sticks. I did find that my naming it a Cantilever bridge was a bit of a misnomer; the activity is similar to the Take It From The Top activity from the Exploratorium.



Initially students tried to use some of the meter sticks as their own counterweight so we had to specify that the farthest extended meter stick had to be the top one. Students were to calculate the hypothetical Center of Mass of the system based on their measurements and assume no thickness to the sticks. The record for paint sticks was 41.4 cm and the record for meter sticks was 120 cm off the table. Groups would go back and forth, adding millimeters at a time as the record was erased and rewritten on my front board. It was a tense day in Physics!


Day 2: Mass & Spring
To review oscillations and simple harmonic motion (SHM) I adopted a lab practical challenge I had read about but unfortunately can't remember where. Students were challenged to hang the correct mass from a spring so that it's period was as close to 1 second as possible. Again their instructions included the rubric so they knew how to earn points. Students are given no other information however, and have to first determine what they need to know about the spring in order to find the needed mass. Once calculated, students would hang the mass and spring from a Vernier Dual Range Force Sensor and start it oscillating. They would use the software to determine the period for five cycles then divide by 5 to find the period for one cycle. Each class was assigned a different target, 0.5 s or 1 s or 1.5 s. I had used stiff, old springs that students had not worked with before so that they had unknown larger spring constants. This meant that the 1.5 s period required a large mass and so I changed it to 0.75 s for that class. Students used the Vernier probes to calculate the spring constant as well and so everyone got very accurate results as seen at below.


The second stage of the competition was to determine the mass of an unlabeled or hidden mass using the same procedure but in reverse. I used several old masses found in the back of my cabinet that had had their labels worn away over the years. I also made unknown masses out of toilet paper tubes and dead batteries. Each mass was measured and recorded so that I could see how close each group came. If they calculated the unknown mass to be within 10% of the actual they received group points. The group closest to the actual mass received bonus points; bonus points were also awarded for the group that got closest to the assigned period.

In the future I think I will decrease their accuracy by only providing a spring scale for the initial determination of the spring constant. This will make it harder for groups to get so close to the assigned period and award groups that employ careful lab techniques. I would still use the Vernier probe to determine the period of the oscillating mass.

Day 3: Flying Cups
Since our competition started during the second week of AP testing there were still students that were occasionally gone to take AP Exams. On those days they did not earn their individual points for participating in the PhysX games but they were also not penalized for missing them, it was excused. If they were *cough cough* "sick" that day however, they would have to complete a make-up activity. If the equipment could be easily gotten at home they could do it there but some competitions required sample data for their alternates because students did not have the equipment at home. 

The Flying Cups competition however, could easily be done at home. I saw this for the first time at an elementary school Science Night and immediately decided to do it in my classroom. This video (also below) explains the how to's and the teacher flies several different models. Essentially two identical cups (made of paper or thin plastic) are taped together at the bottom. A chain of four or more rubber bands is made and wrapped around the center of the cups and held on one end. When the cup is released and the rubber band chain pulled the cup is launched forward. 
Each period, 30+ AP students were completely engrossed in flying these cups. They tried all kinds of models, trying to figure out if paper or plastic worked better, a longer rubber band chain or shorter, more rubber bands or fewer, added mass at the center or the edges, etc. In the end a few smart students realized that launching from on top of a picnic bench gave them a distance advantage. Soon everyone caught on and eventually the whole class launched from a small hill in the center of our school. Some students were better launchers than others, one of the more successful being a varsity baseball pitcher. Groups earned points for each meter their cup traveled before striking the ground (not rolling) and had a bonus for the farthest in each class. By the end of the day the record was 14.7 m, with most groups over 9 meters. It was a simple activity, definitely mechanics but very fun.

Day 4: Leyden Jar
This was an activity that I used to do for years in my regular Physics and even Conceptual Physics classes. I taught students about parallel plate capacitors by having them build a simple Leyden Jar out of a film canister. I still hoard film cans to this day even though I haven't had time in the curriculum to do this for years. For the competition students were instructed to use a small film can, or a jar if they brought their own, to make a simple capacitor. This old video of mine shows the basic construction:
I had asked students to bring in cups for the flying cups activity and jars for the Leyden Jar activity without telling them what it would be for (so they didn't research it in advance). A larger jar would increase the capacitance their jar could hold, something they realized too late. Students were challenged to build a Leyden Jar that would hold a charge and then asked to hypothetically calculate what the capacitance should be using the cylindrical parallel plate equation they found in their textbook. After their calculation we charged up their Leyden Jars with my Whimhurst machine and measured the capacitance using my new capacitance meters.

I found that you have to be careful to stop charging the jar before it discharges itself, something that happened quickly for sloppily made jars. I used alligator leads to connect the Whimhurst machine (with discharge electrodes far apart) to the inner and outer surface of the jar being tested. At least one of the leads had to be removed for testing or you would measure the capacitance between the much larger Leyden Jars of the Whimhurst machine.

Students got HUGE errors between their theoretical and measured capacitance, as in the hundreds of percent. I need to improve the testing system if I ever want points to be awarded based on their error. Students had to research the dielectric constant of their jar, be it plastic or glass, and there is a lot of variety in that value depending on the actual material. Also without a pair of calipers students had to try to estimate the thickness of their jars as best they could. One creative group asked to borrow box cutters to cut off the thicker lip around their film can so that they could more accurately determine the thickness.  Generally the smaller film cans had a higher percent error and a smaller capacitance. The large jars brought from home tended to be more accurate and their larger surface area gave them a larger capacitance. My students were able to produce capacitors from 10 (film cans) to 100 (glass mason jars) picofarads.

While I liked the review of capacitance, specifically what it was and what physical attributes of the capacitor affects its capacitance, the build was pretty easy. There wasn't too much difference between the capacitance of a well made or sloppily-made jar from the same film can. One student made a simple flat capacitor about 4x6" just for fun and it had a capacitance several orders of magnitude larger. Another variation may be to assign a certain dielectric material, plastic or paper or cardboard, etc. and a certain capacitance. Students would have to determine the size of the parallel plate capacitor for that particular thickness of that particular dielectric to achieve that particular capacitance. I feel like it would be more accurate, easier to test and I could judge them based on their accuracy to their hypothetical.

Day 5: Mystery Circuit
This was a variation on my Electric Building (House) Project for regular Physics and Conceptual Physics. I gave each group a shoebox that had a lid with their instructions and made paperclips, brads, wire cutters, wire strippers and holiday lights available. Unlike the previous project students got to design whatever circuit they want as long as it met the conditions:
1. Uses only one 9 V battery.
2. Has at least 8 lights.
3. Has at least 2 switches.
4. All lights can be lit up, all lights have to be able to be turned off (for storage).

Groups were to design their circuits, build it so that just the lights were visible on the outside of the box (rest of wiring hidden on the inside) and make a matching circuit schematic. That earned them the minimum points for accomplishing the task. When they were done each group were to exchange their mystery circuit box with another group and try to guess the schematic. Each group that they successfully stumped earned their a bonus point. I told them that it was quite possible that each group would be stumped and earn points after the exchange.

We did have a few hiccups on this one that I was not anticipating. In my first class of the day we found one LED strand of lights that was masquerading as an incandescent one. Since LEDs are directional it was very difficult for students to build a working circuit with them. And since relative brightness of bulbs is usually how students guess how bulbs are connected the equally bright LEDs wouldn't work for this task. Some of these groups got pretty far into their build before the mistake was recognized and ratified. I had also expected that since students had built a simpler circuit in the same way last year in regular physics they would be able to build this more complicated one quickly. I was wrong. We ended up taking two days to complete this and some groups never did.

There were a few groups that made their circuits so complicated that even they weren't sure how it worked, or the load was too high and it never did. Hurried and/or loose connections made it difficult to judge if their circuits matched their diagrams. Some made simple light connections but used the switches to complicate it, which was more of what I was hoping for, like below:

In the future I think I will limit the number of lights, switches and perhaps more strongly emphasize that all lights must light (not that "Technically a microamp could be flowing through it even though it looks off"). I will have to give them more instructions on how to make the switches, strip wires, etc. I expected students remembered those skills from the previous year; which assumes they did actually build the project they turned in. In the end the activity worked but I wasn't really satisfied with the quality of the project or their efforts.

I had also hoped to keep this year's projects (hence the requirement that they had to be completely turned off) so that perhaps the next year I just asked groups to map the mystery circuits made this year. So few were working a week later when I went to dismantle them that I had to abandon this idea and instead scavenged them for parts. Side note: I take apart all but the very best Electric House projects each year to save the parts (brads, paperclips, bulbs, 9Vs, motors) for the next year.

Day 6: Defibrillator 
I got this idea from Frank Nochese on Twitter about challenging students to build a defibrillator model like an RC circuit. I researched defibrillators and put a call into my sister who is a registered nurse to get the low down on how they were actually used and how that related to the circuits my AP students had used. Turns out that the typical movie scene is completely wrong (and a pet peeve of medical professionals everywhere). Usually a patient is shown flat lining (no more heart beat) and it is then that a defibrillator is applied and the doctor charges it up and shouts "Clear!" and a big thwump is heard as the person/ body jumps up on the table. This is repeated until a heart beat is restored. In reality the defibrillator can only be used when there is still a heart beat but it is irregular. A loss of a heart beat means that chest compressions must be applied in order to restart the heart and get it beating again.

When I researched how they actually worked I found that the first prototypes used AC current and modern ones used inductors. I didn't have any inductors so I opted to still use Frank's original plan using an RC (resistor-capacitor) circuit. Real defibrillators use inductors so that the current oscillates, the oscillation can be controlled to match the desired heart beat. An RC circuit model would simulate one "beat" if you will because it would only charge and discharge once. My research led to a few additional questions about defibrillators and the more physics related concepts that I've added to the bottom of the instructions page.

Groups were told that they could use whatever resistors and capacitors they wanted to meet the requirement to save their "patient." I made little paper hospital gowns to go around the "patient" resistor so that students wouldn't get confused when they had multiple resistors in the circuit. It needed a little paper cot as well. These just might turn into fabric ones by next year ...

Each class was assigned a specific "patient" resistance, the maximum current that could go through it and a maximum charge on the capacitor. Groups had to first figure out what their circuit might look like then use those maximum values to determine the specific size capacitor and total resistance to use. I had 100 or 2200 microfarad or 1 farad capacitors for groups to choose from. Almost everyone ended up using the 2200 microfarad. I had a shoebox, literally, of organized resistors for students to work through. They were not as organized when we were done. Some groups couldn't find exactly the value of total resistance they needed but found getting within a few ohms was fine. A few groups wanted to stick to only one resistor (or mistakenly thought that the "patient" resistor was the only one allowed in the circuit) and therefore tried to add a few capacitors in series or parallel.

Once students had built a circuit that allowed them to charge their capacitor (not through their patient) and discharge it through the patient they attached meters. We could probably have done it with multimeters as Frank did initially but I opted for our Vernier voltage and current probes since we had them. Since the currents were in the milliamp range the graphs are so small. Most groups got a good decay curve for the current through the "patient." I had wanted students to also measure the voltage across the capacitor and the resistor but often this was not done due to time.

Next time I won't have all my resistors out. I shudder to think of the order of the envelopes of resistors in that box when I go to look again. I would still have a variety but will try to pair down their options. I did not assign the additional context questions (below) that I wrote this time, they were my backup in case it didn't work at all. Next time I would definitely include them as I like them and think they bring some background to the activity. Other than that I think it was a great lab practical for RC circuits that Frank came up with and I will definitely use it in the future. This is one that I would like to add to my regular curriculum, if we have time. 

Day 7: Trivia
This was the Tuesday after Memorial Day weekend, the last real class day before finals. I thought the last day of competition would be a good day to review the material for their final. Rather than using a Jeopardy type format, in which can be slow and often leads to one group keeping control of the game,  I opted for a pub trivia format. If you aren't aware a lot of pubs or breweries have Trivia Nights that include teams that come back each week and multi-month tallies of points. Rather than having groups shout out answers or use a buzzer groups submit their answers to questions in writing. Everyone who gets the answer right can get the point, the question move along quickly and you can maintain a bit more decorum. I wrote up over 60 questions spanning the whole Electricity & Magnetism semester, some were multiple choice, some shorter response and some calculations. Each question had a timer for either one minute (conceptual) or two minutes (calculations & short responses) on the slide itself. 

Before we began I went over the rules with each class:
•All groups will be asked the same questions and record their answers on a sheet of paper to be turned in and graded later.
•NO CELL PHONES OR OTHER ELECTRONIC DEVICES, TEXTBOOKS OR NOTES ALLOWED. These are questions to be answered by your brains alone.
•Do not shout out answers. Do not talk to other groups. Whisper with your group.
•Groups earn points for each right answer. The group with the most points will earn an extra 5 points.
•Each question has a time limit before the next one is shown but you can write answers to previous questions if you have extra time on another question.
•You can have more than one paper and pencil out but must turn in one answer sheet.

Groups used whiteboards for their work or discussion/ debate drawings but kept all their "final answers" on a separate piece of paper I would collect at the end. I was able to sit down and read each question as it came up, the counter ticked by and then moved the slide forward for the next one. Students kept on task and most groups attempted all questions. Sometimes there was a lull as they answered a question in less time than was given but sometimes they ran out of time. I encouraged them to record information  for questions they ran out of time for so that they could go back on questions that they had extra time for. In the end I collected all the papers and graded them, awarding a point for each right answer. Since there was only one per group it did not take long and sometimes I offered partial credit. The group with the most questions correct also got the bonus points.

What was difficult was the mixing of the questions. We weren't going to get through all 60+ questions in each class so I tried to skip around so that they got a sampling from each major unit (electrostatics, current electricity, magnetism, etc.). This confused some of them as they had to number their answers with the question number which may not have been the number following the last one. There were some questions I wanted every class to get and I found myself having to record on a scratch piece of paper which classes got which question. I'm sure there is a program or website that would improve on this model and I'll have to look for it before next year.


In the end the competition did what I needed it to do: engage the students in some fun physics exploration until the end of the school year. I think my students enjoyed it, especially since they didn't have homework, but it could use some improvements. For one, I don't think it did as good of a job helping them to review for their final exam. Their final exam scores were lower than I would have like, especially since for many it was their only "real" final exam after earlier AP finals. I expected the activities to keep them thinking about the content, which to an extent they did, but it did not help with remembering the finer details and tougher problems they needed to review. Many thought they still knew the material well enough not to have to study, a problem unrelated to the competition.

The points for several groups in each class were quite close, the winners only being a point or half a point ahead of the rest. It was nice to see though that different groups won different competitions. A few groups won twice over the course of the competition (thus earning bonus points) but it was not necessary to be the winner in each class. I would want to tighten up the system of awarding points, try to find activities that require more content knowledge for this semester and increase the difficulty of some of the activities. It wasn't bad for a first run but I anticipate the PhysX-Games of 2019 will be much better.


Friday, June 22, 2018

Rio Phyz 2018 media shoebox

There is no history unless you record it. I used to be much more active in getting candids in class of students conducting lab activities.

But I still like to get some from ExploratoRio. So I get students to snap up what they can during the event. I sifted and sorted, then cobbled together a slide show in the Mac OS Photos application. Set it to a bit of music, then uploaded it to YouTube. Turns out, you have to set the video to "private" when you use copyrighted music. So that's what I do. Here's the link.

Fascinated: The ExploratoRio 2018 Slide Show


I still break out the camera for Egg Toss and Van de Graaff generator activities. And class portraits on the day of the final exam, immediately following the issuance of the class's PhyzMaster certificates.

Here's the photo album.

Rio Phyz 2018 Photo Album
2018 00 Rio Phyz

Monday, June 18, 2018

The psychological implications of climate change

The rising tide of factual observations continually encroaches on the Island of Climate Denial, leaving fewer and fewer occupants. They become more desperate with each new wave of data.

The rest of the world moves on.

One aspect of that is the acknowledgement that climate change produces psychological problems.
A recent report from the American Psychiatric Association urges people to "participate in policy and advocacy to combat climate change." 
And that's just one of the medical groups writing about the connection between adverse mental health effects and global disasters related to changing climate.

NPR: Here and Now:A Connection Between Climate Change And Mental Health — Experts Say It's Time To Take Notice

Tuesday, June 12, 2018

Cosmos: A Spacetime Odyssey - Video Question Sets

First and most importantly, a third season of Cosmos is in production for a Spring, 2019 release. I believe the appropriate term of art here is "Squee!" My Close, Personal Friend, Neil deGrasse Tyson will once again be hosting. The complete title is Cosmos: Possible Worlds. Cosmos aficionados may refer to it as Cosmos 2019 or Cosmos: PW. I look forward to its addition alongside Cosmos: A Spacetime Odyssey (2014) and Carl Sagan's Cosmos: A Personal Voyage (1980).



In other Cosmos news, I have created video questions sets: student sheets and answer keys to accompany Cosmos: A Spacetime Odyssey. Each of the 13 episodes gets a two-sided sheet of questions that students can answer while the episode plays. Question types vary, but are intended for quick, short responses.

Some video question companions launch into deep, probing questions that take students out of the presentation. Not these. The goal of these questions is to help students maintain focus on the episode while it plays. I leave the deep questions to classroom instructors.

I've added this set to my Teachers Pay Teachers Store: The Lessons of Phyz. My question sets for the now-extinct high school adaptation of The Mechanical Universe are already posted there. Who knows what will be next.

In any case, here's a direct link to the Cosmos set:

Cosmos: A Spacetime Odyssey - Video Question Sets

I have used these sets in my AP Physics 2 course and in my Conceptual Physics course. We watch approximately one episode per unit as part of the ongoing skepticism and critical thinking component of the course curriculum.

Thursday, May 17, 2018

Breaking: The Yanny/Laurel Divide

UPDATE: Well, this is a rabbit hole you might enjoy: The New York Times made a Yanny/Laurel slider. Spend some time with it. It harbors surprises that intrigue. Perception is pliable. 

New York Times Yanny/Laurel Slider

It seems to be a matter of utmost international importance that I share this cogent audio demonstration involving the consumptive "Yanny vs. Laurel" debate.

YouTuber Dylan Bennett presents
1. The unaltered audio clip.
2. The clip with the high-frequencies masked.
3. The clip with the low-frequencies masked.

Yanny / Laurel - Removing High/Low Frequencies



As we age and/or do damage to our ears, it's typically the high-frequency response that goes first, as I understand things.

Reports are that this is a machine voice tasked with pronouncing "Laurel". Many folks with high-frequency hearing loss seem delighted to hear "Laurel". Many with acute high-frequency hearing detect "Yanny" with no ambiguity. Some folks report hearing both or that what they hear changes from one to the other. ...Auditory Switzerland?

I hope this brings peace to the many for whom this polemic has harshed an extant calm.

Tuesday, May 08, 2018

Physics Girl's twist on polarized light

If you're not subscribed to Dianna Cowern's Physics Girl channel, you should fix that as soon as you can.

She's got a nice episode on polarized light that covers the basics and extends into ... things I didn't know! As Paul Hewitt would say, "Yum!"

Take a look for yourself. If you already knew about human visual sensitivity to polarized light, you're ahead of me. (Not really a high bar, but still...)

Physics Girl: Only some humans can see this type of light


It was so much fun, I wanted to show it in class when I teach polarized light. Of course, I have that condition (?) that compels me to write up a questions set that students complete while they watch the video (and a bonus question for after).

That question sheet can be found at the link below:
YouTube Physics: Only some humans can see this type of light (PDF)

Saturday, May 05, 2018

RL Falstad Circuit

During my electromagnetism unit in my AP Physics C course I wanted my students to investigate a resistor-inductor circuit to reinforce the relationships for potential difference and current. Resistor-inductor circuits and resistor-capacitor circuits share a lot of similarities, including difficult-to-derive equations. While the derivations are a bit complicated they follow a similar format and once students have some practice they should see a pattern. Here is a write-up I made for my students for the resistor-inductor circuit equations. I tried to emphasize the patterns of decay and rise of each to reinforce the behavior of the current and potential difference over time. In a resistor-inductor circuit the current is initially zero when the switch is closed as the inductor produces an emf equal to the battery but in the opposite direction. We say that the inductor acts like a broken wire when the switch is first closed. Over time the current rises exponentially and the inductor produces a smaller and smaller emf until eventually the inductor acts like a solid conducting wire. As the current rises, so does the potential difference across the resistor.

As the switch is left closed for a long time the current of the circuit reaches the maximum current as if the inductor was not there at all. If the circuit can be completed without the battery then the inductor will initially produce the same current as before the battery was removed. The current decays over time, therefore the potential difference across the resistor does as well.
When my students were learning about resistor-capacitor circuits I had them use real lab equipment and confirm the potential difference and current equations they had derived. But I did not have inductors to use in a lab for a resistor-inductor circuit. I found this Falstad simulation and it is amazingly powerful. You can make any complex circuit you want! Below is one I mocked up for a homework problem. I screenshot the circuit and added more text to explain it to my students.


I constructed the circuit I wanted my students to explore and exported a link to the circuit. That is something I plan to do again; I can construct a problem-specific simulation and save that simulation forever as an exported link or screen capture. In the #GraphFails post I shared some terrible excel graphs my students had made. Since they obviously need more Excel practice I also decided to make a portion of this lab an Excel lesson.

Students started by drawing a Resistor-Inductor circuit and the appropriate meters to measure the potential difference across the inductor, resistor and the current through the circuit. They were to pick any value they wanted for the battery, resistor, and inductor. They used those values to write specific equations for the potential difference across the inductor, resistor and current when the switch is first closed and then as the switch is moved to exclude the battery. They calculated the time constant and maximum current for their circuit.

Students then opened either Excel or Google Sheets to create their data. I taught them how to make a data table and apply simple equations to fill in their data tables. The equations for resistor-inductor circuits were not the easiest thing to learn to type into a spreadsheet so my instructions included a simple method and a more complex one. By graphing their data students were able to confirm that their equations and data were correct if the shape of their graph matched their expectations.
Students learned to label all the parts of their graphs, resize them, change their legend, etc. They printed out their data tables and graphs for both the rise and decay of current.
The final step was to follow the link to the Falstad simulation and create their circuit. Since I had set the circuit up students just had to right click on each element to change the values to what they had set up in the beginning of their lab. Students then ran the simulation watching the current rise and then change the switch after it leveled off (after 5 time constants) and decayed. They were able to pause the simulation and doublecheck that their values determined by equations matched the simulations.

Overall I felt like it was a successful lab simulation. Students practiced complex equations, double checked their graph predictions with computations, learned how to use Excel/ Google Sheets to write equations, create multiple graphs and customize them, and created a visual of their personal circuit to see the values change with time. In the future I'd love to get a real resistor-inductor circuit lab going but I think that I would add it to this lab rather than replace it.

Lots of students surprised themselves with their accuracy, some getting too excited, "We have no error!" That was inevitably followed with the slow realization, "Wait, everything was done with equations ... we shouldn't have any error." No, you should not. So when a student did produce a graph that disagreed with their prediction they were able to work it backwards to find out where they had made a mistake. All in all Falstad may be my new favorite electric circuits simulation. Shhhh.... don't tell PhET. ;)

Sunday, April 22, 2018

Tuesday, April 17, 2018

How to teach a class you've never taught before

Short answer: work hard.

Oh you wanted specifics? Keep reading.

One of the intricacies of education is that we can do the same thing year after year but nothing is the same or we can teach a completely different class and everything is still the same. Here are two examples:

I taught Physics every year for ten years. In that time period there have been new national and state standards implemented, two major bell schedule adjustments changing the number of minutes per day and week, furlough days have come and gone, new rallies and school traditions take instructional time, I have changed rooms four times, decided to forgo homework and gotten a new textbook twice. While I have taught "Physics" for ten years the class I would teach now is not the same as when I started.

I have also taught Conceptual Physics seven times in ten years. Several times there was a year in between in which I did not teach it. The population changed from freshmen only to freshmen and English Language Learners to open to all students to freshmen and special education only. The book has not changed but I have also had the same schedule and calendar changes I experienced for Physics. Because the class was meant to sere students that need additional support many of the pedagogical approaches and project based learning remains the same.

It can be hard to teach a course you have taught before with textbook or schedule or population or calendar changes. And then you may have to teach something completely different. Physics teachers often have to teach non-Physics courses because of traditionally lower enrollment in Physics classes compared to say Chemistry. In some schools they are the only Physics teacher and thus teach multiple levels. We tend to have more preps (different classes to teach) and change them up more often than other science disciplines. In your career you will probably at least once have to teach a brand-new-to-you course that makes you feel like a new teacher all over again. That's what happened to me this year with AP Physics C.

While I would love to say I met the challenge gracefully with my years of experience that was not always the case. Sometimes the workload crushed me. It definitely left my family neglected, our house in disorder and our lives chaotic. But as the end of the year approached I found that it got easier, not because the curriculum did but because I had developed a process. I found, through absolute trial and error, what helped me and what did not. I realized I went through the same steps in the same order at the start of each unit and it started to get (incrementally) easier.

And thus I decided to share, not because it is innovative or particularly amazing but because it could be helpful. I know someone out there, experienced or not, will be told in the coming weeks that they will be teaching (gulp) some class brand-new to them. It is daunting, makes you question whatever skills you thought you had and the workload downright sucks. So if some of this process helps you, great. If not, hopefully it helps lead you to your own.

Start with what you are given:
If you are inheriting the course from someone else you may find that you have also inherited a few filing cabinets worth of material. Or binders. Or shelves and shelves of "teacher resources." It is time consuming but worth it to go through this materials and do a first sort of what is and is not useful. Ditch the floppy disc versions of your textbook's teacher materials; ditch multiple copies of supplemental materials (unless there is more than one teacher). Check with your district about district copies of these resources, they may wish to consolidate extras in their warehouse for potential future use. You don't have to read every piece of paper left for you in a file cabinet now, you don't have to decide to adopt everything they left for you but you may want to keep it to give yourself the option.

As I moved into my new room this year there were eight total file cabinet drawers left for me for Physics and AP Physics. In my first sort I kept one copy of everything. I wanted to be able to read the labs he wrote but figured even if I decided to do the same ones I would probably be retyping it. I wanted to be able to see what his tests looked like, but knew I didn't need a class set. I kept a copy of his handwritten lecture notes so I could see how he implemented material, even though I planned to make powerpoints. I kept the manila folders, overheads and single sided paper to reuse as scrap paper. In the end, I filled four full size recycling bins with the paper I discarded, that was just the double-sided stuff. What I kept fit in two 4" binders in page protectors. I separated the stuff by unit, or at least by what I thought was by unit at the time. I was left with no digital files, except for uneditable pdfs I was able to download from  his website before the district took it down.

As the year has progressed I started every unit going through what I was left. I looked over and digitized the lecture notes (you can copy it into a tablet or just scan it) to see how the material was presented before. If there was a worksheet that I wanted to use I would retype it as it was at first. I then did the worksheet myself and edited it how I wanted to for my own kids. Basically I took a look at what was done before as a guide, not to follow exactly but just for comparison. It provided a place to start, so I didn't have to start from scratch. There were plenty of worksheets, labs, etc. that I took this second look to and tossed aside. If you are lucky enough to start a new-to-you course that someone else teaches, start with everything they have. You can change things but it is invaluable to see how someone else teaches it, for better or worse.

Textbook resources:
While you may or may not use your textbook, electronic or print, your district has probably adopted one. Looking through it can be helpful if you have to learn or relearn material. I would read and take notes on each chapter, so that I could experience how the material was introduced just like my kids would. Most publishers have digital teacher resources now, either for download or on their website. My publisher has answer keys, lecture powerpoints, test banks, image galleries, simulations and more. So as to not re-invent the wheel, for each unit I started my lecture powerpoints using the textbook ones as a base. As the  year progressed less and less of the original remained but it saved me time when I had so little. While using pre-made resources is not ideal, you should personalize your curriculum for yourself and your students, it is not the worst starting place. In later years of teaching the course you will probably use your own materials more and more.

Find reliable resources:
No class should be taught by textbook alone. Finding a few trusted and reliable resources for your class is important. This may be a professional networking site or another teacher's website or even social media. I found helpful materials on a wiki page, PrettyGoodPhysics, that will sadly need to relocate. There were a few YouTube Channels that provided consistently good tutorials by subject for myself and my students. Sometimes it would be for a different course (AP Physics 1, 2 or Honors Physics) but good video lessons are good video lessons regardless. I recommend Flipping Physics, Dan Fullerton's APlusPhysics, Mrs. Twu's video tutorials and  AKLectures Physics series. If I needed to review a topic, or more importantly to learn what to emphasize for my students, it was very helpful watching other teachers teach it.

Social media turned out to be one of my greatest resources this year. I was able to find other physics teachers I did not know on Twitter and could follow or use hashtags like #APphysicsC to find resources by course. I was able to share data that didn't make sense and tag the equipment manufacturer who would often very quickly respond with suggestions. I once tagged @VernierST in the middle of a class period about weird looking data and got a response before my students left that period. They would continue to work with me for days as I tried to troubleshoot. Other teachers could jump on the thread and make suggestions or share sample data in the worst case scenario that nothing worked. I could share pictures of student work that made me scratch my head, asking more experienced teachers how I could prevent such incorrect problem solving in the future. As other teachers shared pictures of labs or demos they were doing I could save the picture for future use. I've even reached out to individuals to ask for their lab write-ups, ask follow-up questions or for advice. And they respond! Teachers usually like to help other teachers and many have been amazingly generous, sending me full curriculum guides, sample lecture notes, etc.

And perhaps most importantly, they don't judge much. On Twitter and on the College Board AP Physics C list serve I have posted problems that I cannot solve, or conceptual issues I still have that are preventing me from teaching it to my students. More experienced teachers have been able to respond with suggestions, solutions or alternate ways of approaching the problem. Everyone was patient as I usually started out my requests with "Since it's my first year teaching #APphysicsC..." And since I was putting that question out to anyone who could answer, people that could would and I would crowdsource some great solutions.

I also collected textbooks. Luckily we just adopted new AP textbooks so we had a textbooks from all the big publishers who had sent materials during the adoption process. I currently have six textbooks on my table, and I would often flip through all of them. For each chapter I would look through them to see if the example problems were different, how the material was grouped or arranged and to see what was emphasized. If my adopted textbook emphasized a type of problem that didn't appear in the other textbooks it helped confirm what was outside of the scope of the class.

Ask for help:
You know you should but it may still be difficult to admit that you don't know everything (yet) about your new course and you need help. Sometimes it was about the scope of the course, as my textbook includes a lot more than what is included on the AP Physics C exams. Sometimes the problem I tried to do out of the back of the chapter or on a worksheet I found was coming out wrong or I didn't have the answer to check it. Whatever it was I found that there were a few people I could ask for help. Most I knew personally through NCNAAPT but some I had met through my AP summer training or interactions online. I tried to spread out my questions, rotating through my "will help me" rolodex so that I did not take advantage of those willing to help me. I tried to figure it out by myself and not have to ask unless I was really stuck. My friends seemed to know this and did everything they could to help me when I asked.

Get trained:
I am a firm believer in proper science teaching professional development. Not all PD is good, don't get me wrong, but there are some consistently helpful training opportunities I always enjoy. For new teachers PTSOS and the Exploratorium's New teacher Institute of course. The national AAPT Summer and Winter meetings and your local AAPT meetings are full of the best-of-the-best resources shared among physics teachers. I find that the down-time in between workshops with other teachers can spark the best conversations and lead to lots of good shared ideas.

If the new-to-you course is an College Board Advanced Placement one you can also take a sanctioned AP training. They can be pricey but are often offered throughout the year. I had a hard time finding summer training for AP Physics C last year and had to travel to Texas to attend one. While it was helpful, I did not feel that one was enough to be comfortable teaching the course. I asked my district to send me to another one this summer and I'm crossing my fingers that there is more to learn.

Practice Practice Practice:
I found that, much like my students, I benefited from lots of practice. While I wouldn't do every problem in my textbook, I would probably work through twice as many as my students. I tried to do every conceptual question and did the ones that another AP Physics teacher using my book assigned. I figured that this more experienced teacher had probably already weeded out the problems that were too hard or awkward and these problems would be good for my students. Sometimes these still tripped me up and I decided early on that if I couldn't do the problem, I would not assign it to my students. By doing more problems I was able to see patterns in how the questions were asked or what they were asking for as well as improve my own problem solving technique. This also meant when it came to assessments I had more problems that I could solve then I had given to students to use.

One particularly helpful resource was an online workbook of released AP multiple choice and free response problems arranged by subject. This meant that I could look through the simple harmonic motion section and see all the problems ever asked on the AP exam about SHM. I could pick and choose the problems I wanted, combined with the textbook's test bank, to make my own tests. Sometimes working through all these extra problems seemed time consuming, especially if I wasn't going to assign them all, but overall it really helped my understanding.

Get organized:
This is easier for some than others, and I am not saying that everyone has to be a super clean desk all the time, but, if you are collecting new resources for a new class that doesn't do you any good if you can't find the cool thing your saved when the time comes. The easiest method is to create a folder for each unit and throw it all in there. At the start of the year I made a folder for each section of the AP Physics C objectives so that when I found a few resource I could sort it appropriately. This meant that prior to the start of the unit I would have maybe half a dozen to a dozen files before I really started to build the unit. As the unit progressed I would sort what I was using from the extra resources I wanted to keep from the assessments I would give. Since I tended to save everything I could get my hands on I would end up with a lot of files. For example, I started my magnetic field and forces unit with 5 digital files and two weeks later, before I've even written their test, I have 150.

Take care of you:
At the risk of sounding like a spa commercial, you need to take time out for yourself. Even though I was part time, developing new curriculum this year became my life. It was not unusual for me to work 12 hours a day, as in actual sitting down work, not just being awake for that long. I neglected my hobbies, cleaning, my health, because the work "had to get done." It will be the most work you've done outside of your first year to develop a new curriculum. Apologize to your family up front. However, do not lose yourself to it. Prior to this year I was trying to work on life-work balance and I failed miserably this year. I wish I had taken more breaks, spent more time with my kids, etc. but I didn't know how to get all my work done and do everything else. It got better as I developed this process and that's why I'm sharing. Hopefully having a game plan will help you develop your new-to-you course without drowning in your work. A burnt out teacher is not a helpful teacher.

To summarize:
1. Start with what you are given.
2. Try textbook resources.
3. Find reliable resources
4. Ask for help
5. Get trained
6. Practice Practice Practice
7. Get organized
8. Take care of you.

That's it, just 8 easy steps! (Totally sarcastic by the way)

It will be tough but by trying to focus on what I knew worked for me, I've almost gotten through it. As I can almost see the bright light on the other side believe me when I say you will too. Good luck!