When classes had to go remote or online due to the pandemic, the biggest issue for general physics courses was, among other things, the labs. These courses were not designed to be done remotely, and so the labs could not simply be adopted for remote learning. This is in contrast to online general physics courses that were designed to be done remotely and have lab kits designed for such courses.
I had to resort to using virtual web applications and simulations at first, making extensive use of the PhET website, until I discovered Pivot Interactives. But this is not about that. Rather, I also had to think a little bit of actual activities that a student could do using simple, household stuff, that can either be their "experiment", or a supplement to any simulation or online labs that they did.
When we started a topic on electric charges, I used this as an in-class activity to supplement the lecture as a demonstration of static charges. When we went remote, I changed it so that it became an experiment that the students could do at home because it uses only one thing: sticky cellophane (Scotch) tape. I'm sure this is familiar to many people, but I'll describe briefly what is involved.
You take 4 strips of sticky tape, each about 6 inches long. Fold under one end of each tape so that that end doesn't stick to anything and acts as a convenient handle.
Take one tape and stick it to a flat surface such as a table or desk. Mark one end of it with a "B1" for bottom tape 1. Take another tape and stick it on top of B1. Mark that tape as "T1" for top tape 1.
Do the same for the other two tapes, but mark them as "B2" and "T2" for bottom and top tape 2, respectively. You should end up with something similar to the picture above.
Now take T1 and rip it off B1. Stick the sticky, unfolded end of T1 to the edge of the table so that most of the tape hangs freely.
Pull tape B1 off the table. Hold B1 at the folded end and let it hang down freely. Slowly, move it closer to tape T1 but don't let them touch. What do you see?
Next, attach the sticky, unfolded end of B1 to the edge of the table, very much like what was done to T1.
Rip tape T2 off B2.
Hold T2 at the folded end and let it hang down freely. Once again, slowly move it closer to T1 and observe. Repeat this by moving T2 closer to B1 and observe.
Attach T2 to the edge of the table again, the same as what you did with T1 and B1.
Pull tape B2 off the table, and repeat the process with T1, B1, and T2.
So that is the entire "experiment". The students had to describe clearly what they observed. I emphasized that this part should be just observational. I was not looking for explanation yet. The aim here is to distinguish between observations, which if valid are "facts", versus explanation which can be interpretation based on our understanding.
If the experiment was done carefully, the observation should be like this:
- When B1 is brought closer to T1, the two tapes appear to attract each other.
- When T2 is brought closer to T1, the two tapes appear to repel each other.
- When T2 is brought closer to B1, the two tapes appear to attract each other.
- When B2 is brought closer to T1, the two tapes appear to attract each other.
- When B2 is brought closer to B1, the two tapes appear to repel each other.
- When B2 is brought closer to T2, the two tapes appear to attract each other.
Those are the observations. So the next part is the explanation for the observation. Here, we invoke our understanding of the nature of forces on charges. We know that like charges repel, and unlike charges attract.
Since the two T tapes repel each other, we can conclude that they have the same type of charge. Similarly, since the two B tapes repel each other, we conclude that they have the same type of charge. Next, since the T tapes seem to attract the B tapes, then they have opposite charges. Thus, what we have in terms of the type of charge is
T1 = T2
B1 = B2
T1,T2 have opposite charge to B1,B2.
Now, if given NOTHING ELSE, this is as much as you can say about what you can get out of the experiment. But somehow, every single time I've had students do this, a few of them inevitably went a step further (or maybe a step too far?) and managed to conclude that tapes T1 and T2 have a particular type of charge (say, negative), which means that B1 and B2 tapes have positive charge. I don't quite know how they arrived at this conclusion.
Rather than just telling them that they were "wrong" in the sense that they could not deduce the nature of the charge just from the experiment alone, I decided to use this as a class discussion topic. My main question was that, to what extent can you squeeze all the information out of an experiment based on the observation, and when have you gone a bit too far?
Nothing in the observation alone tells you the type of charge on each tape. What you do get is the relative type of charge when you compare one tape against another. You can't tell which one is positive and which one is negative simply from the observation. You can only tell if two tapes have the same or opposite charges. That's it. That is the limit of the valid and verifiable conclusion that you can draw out of the observation. The experiment tells you nothing about the type of charge that each tape has.
I then asked the students if they can suggest what we can do next to actually determine the type of charge on each tape. Certainly, if we have a "reference" charge, something that we know that has a particular type of charge, then this can certainly be used to determine the type of charge. For example, rubbing wool onto a glass rod has been shown to induce a net positive charge on the rod. So the rod could be used as a reference. But I asked the students whether it is necessary to use this reference charge on ALL of the tapes, i.e. check what happens if they bring this reference charge to each individual tape. The purpose here is to use the inductive deduction, where one only needs to check with just one tape, and knowing that tape's relationship with the others, automatically determines the type of charge on all of them.
But the key thing here is that the experiment by itself can only tell you information about what is going on up to a point. Making a deduction that goes beyond that means that you are either guessing or speculating. While that is fine if you realize that that is what you are doing (we often do that in science research), it should not be confused as facts given by the experiment. They are not. The ability to know the type of charge on each tape requires a reference. Consequently, the validity of our determination of the type of charge on each tape depends on the validity of our knowledge about the reference charge. If, for some reason, our understanding of the reference charge is wrong, then our conclusion about the type of charge on each tape will also be wrong, BUT, our observations are not! The observations are facts, and they remain valid even if we wrongly assigned the type of charge on each tape.
This very simple exercise, and the lessons that can be learned from it, have huge implications to our world today. This is because a lot of people have a lot of problems deciphering and distinguishing between valid facts and conclusions/speculations. Often times, those two are intermingled until one can no longer tell which is which. I've seen people arguing about the conclusions, and somehow, that undermines the validity of the facts that they were based on, very much like wagging the dog. Even worse, when the "facts" are shown to be flawed or discredited, somehow the conclusions that were based on those facts remained alive and well!!
As science educators, we need to make a conscious effort to impress upon the students that science education is not just about learning the science. It is also learning how to think and the process of making systematic and rational deduction based on the nature of the facts.