Robert Prior, ePublisher of OAPT Newsletter
How do you conduct physics experiments remotely? Most students will not have access to much in the way of measuring equipment, but most of them have smartphones that contain a variety of sophisticated sensors. Phyphox is an award-winning app developed at RWTH Aachen University that allows access to these sensors for performing physics experiments.
What raw sensors can Phyphox use?
In 2020 the Ars legendi-faculty award was given to Prof. Heidrun Heinke, Dr. Sebastian Staacks and Prof. Christoph Stampfer for the development of Phyphox and its lasting effect for academic teaching and physics classes at school. This award is selected by the Stifterverband, the German Mathematical Society (DMV), the German Physical Society (DPG), the German Chemical Society (GDCh) and the society biology, bio sciences and bio medicine in Germany (VBIO).
Phyphox can access the following sensors, if they are present on the device:
- light intensity (not on iPhones)
Virtually all smartphones have accelerometers. Apparently, iOS restricts access so that light level can’t be measured on iPhones (even though the sensor is present on the phone). Cheaper phones often lack barometers and magnetometers.
Accessing the raw sensor data can be interesting, because it shows how noisy real-world data collection usually is, and how some level of processing is necessary to get ‘clean’ results. A class discussion on why this happens and what data processing means could be enlightening.
Raw data is interesting, but Phyphox also lets students perform experiments where the data is automatically analyzed and interpreted. In this it is a lot like traditional physics sensor systems such as Pasco and Vernier, where the raw data is hidden and students see only the results of the analysis. Fortunately, the experiments also have a ‘raw data’ tab that shows students the sensor readings — which again can lead to discussions about how real scientists present their experimental results.
Some of the experiments come with worksheets, but unless you can read German (or have a willing translator) they won’t be much use.https://phyphox.org/experiment/
Here are some of the more useful experiments. Some of these experiments were specifically designed by Dr. Sebastian Staacks as home lab challenges, aimed at students under lockdown who only had their phone and common household items.
You can find all the lab challenges here:https://www.youtube.com/playlist?list=PL98JPRgsjFYS6VNJKxp-zzurzUv61ymQKAcceleration without g, Acceleration with g
These experiments just provide graphs of the device’s accelerometers. Why two different experiments? That’s because an accelerometer is actually measuring the force on a small sample mass, so even when the phone is at rest there is a force to be measured. When showing acceleration without g this force is subtracted before showing the data.Acoustic Stopwatch
This experiment measures the time between two sound events (loud sounds).Audio Amplitude
This experiment uses the microphone to provide an estimate of sound intensity in decibels. The microphone is of course uncalibrated, so the results are only approximate, but they are better than nothing. If you have a source of known intensity you can calibrate the offset. This is explained in more detail in the experiment’s FAQ.Beats
This is a neat demonstration of beats using three devices. It is one of Sebastian’s home lab challenges (designed for locked-down science students).Centrifugal Acceleration
This experiment uses the gyroscope and accelerometers to explore the relationship between the angular velocity and centrifugal acceleration. It works well with a salad spinner.Collisions (Elastic and Inelastic)
This experiment uses the noise of a bouncing ball to determine initial height and energy loss.
This one could be tricky to do at home, but it is certainly possible. Sebastian used it as the basis for his first #homelabchallenge (designed for locked-down science students).Doppler Effect
This rather finicky experiment uses the microphone to measure Doppler shift. You need a constant-frequency source, which could be another device with Phyphox running the Tone Generator experiment.
This experiment requires a quiet setting — without TVs, radios, and people talking. Some of our students’ circumstances may not permit this.Elevator Speed
This rather neat experiment uses the barometer and accelerometer to measure the vertical speed of an elevator. To get good results you want about 10 metres of elevation difference (three stories). You could also attach a phone to a quadcopter, as they show in the video.
Note that in Canada you must have a Pilot Certificate to fly a quadcopter, your aircraft must be registered with Transport Canada, and you must observe all applicable laws while flying. Much of Toronto, for example, falls within the control zones of Buttonville, Downsview, Pearson, or Toronto Island airports and is thus Class E Controlled Airspace (which requires Advanced Pilot Certification and an approved NavCan Flight Authorization Request).https://tc.canada.ca/en/aviation/drone-safety/flying-your-drone-safely-legallyFree Fall
This experiment uses either acoustic or magnetic detection to measure the acceleration due to gravity. It can be a bit finicky, and quiet is required, but your students can get good results.Magnetic Field
This is just the raw data from the device’s magnetometer. Nothing fancy, but it can be used to show how the magnetic field strength obeys the inverse square law, for example. Pendulum
This experiment uses the device as a pendulum. Watch the video to see ways that you might use it as a whole-class experiment.Resonance
This is a neat demonstration of resonance. It is one of Sebastian’s home lab challenges (designed for locked-down science students).Sonar
We use sonar as an example of acoustic technology in the Waves and Sound unit. This experiment turns the device into a sonar sensor, allowing students to either measure distance or the speed of sound.
I tried this in class and the results were mixed. The experiment requires a quiet room, so if your class has students without the self-regulation to remain silent then they will not get good results. In a quiet home the results were much better.Speed of Sound
This experiment uses two devices and the acoustic stopwatch to measure the speed of sound.
To do this at home your students will need another person to operate one of the devices. Spring Oscillator
This experiment requires a spring, so many students might not be able to do this at home. A Slinky works well.
To use Phyphox, students will need to download it from either the App Store (for iOS) or Google Play (for Android). The app is free. When it is opened, they will see a warning about damaging their phone, which may concern them — I tell my students that this is basically a warning not to drop your phone when using it as a sensor. (This is one advantage of dedicated sensors like PocketLab: they are more robust than smartphones. For more info on PocketLab, see my review here
Phyphox has fairly active forums where you can ask questions (and get answers!), as well as see ideas for different ways to use Phyphox in class.https://phyphox.org/forums/Creating Your Own Experiments
If you don’t find the experiment you want, you can modify an existing experiment, or create a completely new one, using a web-based visual experiment editor.Legal Details
All material for Phyphox is available under a Creative Commons Attribution Share-Alike license. This means you are free to use the material provided that you correctly attribute it (which we all do anyway). If you modify the material (i.e. produce a derivative work) the same license applies.