## Monday, March 28, 2022

### My Favorite Web Applications - Part 4

Previous posts:

My favorite web applications - Part 1

My favorite web applications - Part 2

My favorite web applications - Part 3

Of course, I have to include a PhET application. How could I not? It is such an amazing collection of very useful applications and simulations.

For this one it is the demonstration on Faraday's/Lenz's law. What is interesting about this is that, if you have read one of my previous posts, I use this not so much as a virtual lab, but rather as an in-class "discovery" tool. In fact, for my f2f classes, I had an identical setup to this PhET application sitting in front of the students at the beginning of class. So the instruction that you'll see given to the students is almost identical for this application and for in-class activity.

This obviously is a lesson on Lenz's law. Instead of starting the lesson with a lecture, I give the students a series of tasks for them to do. I first tell them to set up the application or in-class apparatus to look like the picture below:

We then spend some time discussing the direction of the current in the coil if the galvanometer (in-person) or the voltmeter (PhET) has a positive or negative deflection based on being observed from the right side of the coil.

Once the students have established this, I give them a series of tasks that they have to perform and to record what they observe. The tasks are listed in the table below:

When we were doing this in-person, I asked the students to perform Task 1, to record what they observed, and then we all, as a class, discuss the observation. This exercise was helpful especially to students who were still unsure on what to do and what they should be observing. So this first tasks often clarified further what they needed to perform and what they should observe. For remote classes, this is not that easy mainly because I don't quite see what they students are doing and what they are observing. They are also doing this in their separate Zoom breakout rooms. They have a chance to discuss with members of their group, but I am not always there to double-check what they are observing. I do, however, get to see what they are recording because the table above is posted on a Google Slide document that I give them. So I can see every entry for each group and able to step in if I see something not quite right.

In any case, the students for in-person session perform the task one step at a time, and each time, we all discuss the observation. Remember that I have not told them anything about Lenz's law at all. All they are doing at this stage is performing a task and recording the corresponding observation.

By the end of this activity, both the in-person and remote students will have a set of observations for each of the tasks performed. This is where it gets interesting. I then instruct the students to discuss with their group members on how to come up with a set of rules or "laws" to accurately describe the behavior of the current in the coil in relation to what the bar magnet is doing. In other words, I want the to come up with a written description of Lenz's law.

Of course, I give them hints. The biggest hint is for them to consider the induced magnetic field in the coil. By that point, they have learned that a current in a coil or solenoid generates a magnetic field. If there is a deflection in the galvanometer/voltmeter, then there must be a current in the coil. The positive or negative deflection indicates the direction of the current in the coil, which in turn indicates the direction of the induced magnetic field in the coil.

From my experience in doing this for several semesters, only about 1/4 of the students were able to come up with a description that had a close resemblance to Lenz's law. Many of them struggled not just in understanding what they observed and what the "laws" were, but also in communicating accurately and clearly what they intended to say. The latter is a very common problem for many students trying to write scientific prose.

However, regardless of whether they managed to successfully come up with their own version of Lenz's law, I find that this exercise demonstrates this principle a lot clearer than if I just simply spew out the material in a lecture. Even if the students could not communicate clearly what they understood, most of them actually had some realization of what it is. To me, this is the biggest stumbling block in understanding Lenz's law, which was the impetus for me to present this topic in this manner.

The PhET application allowed me to do almost the same activity online as the one I do in-person. That is a very good thing!

Zz.

## Saturday, March 19, 2022

### My Favorite Web Applications - Part 3

Previous posts:

My favorite web applications - Part 1

My favorite web applications - Part 2

Continuing with this series, here is my next favorite web application. This is a virtual experiment on measuring the specific heat of an object. The fun thing about this particular application is that (i) it is very similar to what we normally do in a real experiment and (ii) one can also use the step-by-step instruction as part of the experimental procedure, thus the name "Guided Specific Heat.... ".

Similar to the force table experiment that I cited in Part 2, this one also has randomized values for each person going through it. It randomizes the mass of the cold water, the mass of the object, and uses different specific heats. Each student doing this online will have a different answer.

When I assigned this to the students during our remote sessions, the students had to fill in all the information obtained during each step, i.e. measurement of the mass, etc. Then, during the actual measurement, once it stopped, the students had to do a screen capture of the graph of Temp. vs. time to paste in their report. They then had to show their work on how they arrived at the specific heat value of the object. If they entered the correct answer, the application acknowledges that and they should also do a screen capture of that to paste in the report. If they got it wrong, then they had the option of either submitting what they had and take the deduction for the wrong work and answer, or redo the experiment from the very beginning. They get to do this as many times as they wish until they get it right.

I also added an extra part where I asked them to think of the kind of errors and uncertainty in the experiment, especially if this were done in real life.

To double-check the students' answers, I created a spreadsheet where all I needed to do was to enter the mass of the object, mass of the cold water, and the final temperature.

I like that each student will have a different answer. It added an extra layer where they could not just copy off each other's work directly. The experimental procedure is also almost identical to one of our experiments on specific heats anyway, so I didn't have to make huge modification to the instruction.

Now that we have gone back to f2f classes, I'm using this exercise as part of a homework assignment.

Zz.

## Wednesday, March 16, 2022

### Are Physics Papers Authored By Women Cited Less Than Those By Men?

So I'm reading this article in Physics Today of a study done on citation numbers and frequency of citation of papers where the first and/or last author is a woman. They found that papers authored by women tend to get less number of citations than men.

The number of papers authored by women in the eight physics subfields examined in the study almost doubled between 1995 and 2020, from around 17% to roughly 33%, as shown in the graph above. But those manuscripts attracted about 3% fewer citations than expected, whereas those whose first and last authors were men were cited roughly 1% more.

What’s more, the gender gap was largest in papers authored by men. According to the study, manuscripts with male authors cited recent male-authored papers about 2% more than expected and cited recent papers authored by women 6% less. Studies with a female author over-cited recent female-authored papers by 3% and under-cited recent papers by men by 1%.

Hum... But then they also say this:

One limitation of the study is that it couldn’t decipher the gender of about one-fifth of the authors, those who list only their initials instead of their first names, Bassett notes. Although Bassett says she and her team excluded those authors from their sample, McCullough thinks a significant number of them could be women. She says women in science often hide their first names to avoid discrimination.

Another problem, Bassett says, is that the software determines the chance of an author being a certain gender on the basis of his or her name, but it will be wrong at least some of the time, especially for gender-neutral names. It also cannot identify nonbinary individuals.

As someone who has read, and continues to read a lot of physics papers, the LAST thing I pay even any attention to is the gender of the authors. In fact, it is a common practice (and certainly in the groups that I have worked with) that when we publish a paper, we tend to only include first-name initials in the authors list rather than full name. It is also from my personal experiences that many of the papers that I have cited turned out to have women as first authors. No one could tell just by looking at the authors list that "K. A. Moler", "N. Trivedi", and "K. Levin" are women, for example.

Coupled with the fact that they found 3% fewer citation for women and that their study had to exclude about 20% of the authors because they couldn't tell their genders, this observation is not very convincing to me.

Zz.

## Tuesday, March 15, 2022

### Gender Differences in Test Anxiety and Self-Efficacy

It's interesting how something things come in clumps. I had just posted a paper on the effect of sharing tasks during lab work on student's interest and self-efficacy in physics. Now comes a study on gender differences in test anxiety and self-efficacy in general physics courses.

Now, to be clear, a large part of this paper clearly indicates that this is not something that physics educator can solve. This is because the issue of self-efficacy starts when a student is very young, and it has more to do with societal and cultural influences.

Performance differences between male and female students in physics courses are often due to sociocultural stereotypes and biases pertaining to who belongs in physics and who can excel in it, and insufficient efforts to counter them in order to make the learning environment more equitable and inclusive. For example, girls are less likely than boys to have parents who believe they can excel in the sciences so parents are less likely to encourage them to pursue related courses and activities from early on [5, 31]. This, combined with societal stereotypes that success in physics requires particular brilliance and brilliance is associated with men, in part explains the low numbers of women in the field [32]. Women are less likely than men to take physics in high school [10], so they are less likely to have prior experience if they are required to take physics in college. Once women are enrolled in physics courses, they tend to have lower SE, which is an important predictor of physics performance, even when controlling for prior academic preparation [19–21, 23, 24].

So already from this, this issue of test anxiety and self-efficacy among girls can't simply be swept away. Instead, this paper proposes how to handle such a thing by emphasizing more on assessment that are low-stakes (i.e. less stressful) and less on higher states assessments, such as exams.

This is definitely something to think about. It is already something that I am doing after we went remote when I consider how easily exams can be compromised. I shifted more emphasis on synchronous and asynchronous engagements that can assess a student's understanding of the material. In fact, in one of my general physics courses that ran synchronously, the total percentage of all the exams for the semester came up to less than 50% of the course grade.

Of course, I was doing this not for the reasons emphasized in this paper. I was unaware of such an effect until I came across this paper a week ago.

Zz.

## Wednesday, March 09, 2022

### Share It, Don't Split It?

This is a rather eye-opening paper on the impact of how students work together during lab work. It seems that when students divide specific tasks among themselves, there is less equitable benefits in terms of physics interest and self-efficacy. This is in comparison to the group of students (Group B) who tend to share the same tasks or take turns in doing different tasks during the experiment.

In particular, we find that Group B-style work is especially beneficial for women, a group that has historically been marginalized in physics. Thus, improving the equity of group work may be a productive step in efforts to improve equity in our field. In this context, we view equitable learning as providing equitable access to physics classes, inclusive learning environments that meet the needs of all students equitably, and learning outcomes that are not biased toward or against any groups of students. In order to improve equitable learning, we encourage educators to find ways to structure student learning to support Group B-style collaborative learning experiences for students.

Of course, this is easier said than done. The tendency here is to let the students themselves decide how they will work together. This means that if we want the students to adopt the working style of Group B, the instructor and the course structure itself has to coerce the students into it. The paper offers several suggestions on how to do this, which you may read in the paper.

This is something that I need to think about more carefully. Is there a compelling enough of evidence to support such an assertion? And if there is, have there been verified and tested methodology that accomplished the stated goals? I sometime feel that, as educators, we are being inundated with a "flavor of the month" of what we need to do for the students in the name of inclusion, equality, equity, accessibility, etc..... etc, and how to execute all that remotely even!

Still, as someone who emphasizes on experimental work quite a bit (being an experimentalist myself), I will need to read this paper a bit more and see if there are any of the recommendations that I can easily do without much modification to the current structure. I know that I have always try to limit the number of students in a group (typically 2 students per group if we have sufficient equipment), so that no one ends up just sitting there and doing nothing but watching and writing down numbers. But this paper may force me to figure out some ways to encourage each student to take turns to perform the experiment and experience every part of the work.

Something to think about, I suppose...

Zz.

## Tuesday, March 08, 2022

### My Favorite Web Applications - Part 2

Previous posts:

My favorite web applications - Part 1

It is rather appropriate that the next web application on my list can actually make full use of the vector calculator that I mentioned in a recent post. Many of you may be familiar with the force table in a General Physics course lab. It is a contraption that looks similar to the picture below.

It actually is a rather useful apparatus to demonstrate vector addition and the powerful and convenient method of vector addition using components. Of course, when I assigned this to my students, we didn't use any vector calculator. The students had to calculate the components and find the resultant vector themselves. But this was also the situation where the students encountered the issue with knowing the correct angle that I mention in the vector calculator post. The only difference being that the visual "obviousness" here is more apparent than just looking at the numbers on an Excel spreadsheet.

When we went remote, I was lucky enough to come across this website that had a virtual version of the force table. In fact, other than not having the students struggle with knowing what weights to use, where to clamp them, and how to set up the pulleys, this exercise is quite similar to what I would normally do in class. I had to do only minor rewrite to my lab instruction to incorporate this web exercise.

The one thing I like about this app is that the situation is different for each student, i.e. the magnitudes and directions are unique to each student. Therefore, while they can consult with each other, each student still has to do his/her own calculations to get the answer. The students are given the instruction that they need to do this until they get it right, even if they exhausted all the tries and have to get the web to regenerate brand new set of forces and angles. Once they get it right, they have to do a screen capture of the acknowledgement page, and paste that in the report along with the working done to arrive at the correct answer.

The only thing I wish this web app has is the ability to specify the number of weights (or vectors) in use. In my in-person lab, I had the students start with just one vector, and they have to construct an opposing vector to get the equilibrium condition (trivial, of course, but you'd be surprised at the number of students who had to think about how to do this). Then they move on to having 2 given vectors, and finally 3 vectors, which is what we have in the web app. By doing this gradually, the students realize that they first need to find the resultant vector, and once they have that, all they need to do to get the equilibrium condition is to create another vector of equal magnitude but in opposite direction to the resultant.

Nevertheless, this is a useful web app and something that I intend to use even for in-person instruction.

Zz.

## Saturday, March 05, 2022

### Solid State Sensors To Detect COVID Virus?

First of all, I'm not sure why this is called "Quantum sensor". Maybe it is because it is using solid-state physics principles?

This is an interesting report, and if the simulation is valid, I'm hoping that such devices will be made real soon because it has the ability to detect other types of viruses. It really is a solid state sensor that makes use of solid state physics principles.

In the presence of viral RNA, these pairs will detach from the nanodiamond surface thanks to a process called c-DNA and virus RNA hybridization. The newly formed c-DNA-Gd3+/RNA compound will then freely diffuse in solution, thereby increasing the distance between the magnetic Gd and the nanodiamond. As a result of this increased distance, the NV centres will sense less magnetic “noise” and thus have a longer T1 time, which manifests itself in a larger fluorescence intensity.

By optically monitoring the change in relaxation time using a laser-based sensor, the researchers say they could identify the presence of viral RNA in a sample and even quantify the number of RNA molecules. Indeed, according to their simulations, Cappellaro, Kohandel and colleagues, who report their work in Nano Letters, say that their technique could detect as few as a few hundred strands of viral RNA and boast an FNR of less than 1%, which is much lower than RT-PCR even without the RNA amplification step. The device could also be scaled up so that it could measure many samples at once and could detect RNA viruses other than SARS-CoV-2, they add.

I find this interesting because as students in solid-state physics, one of the first thing that the students encounter in such a course is the study of solid-state crystal lattice. This includes the type of defects in a crystal lattice, such as vacancies and impurities. So this diamond NV center is exactly those two types of defect in the lattice. Imagine that something you learned during the first couple of weeks of a course in school actually has a humongous application to human well-being!

Chalk this one up as another invaluable application from condensed matter physics.

Zz.

## Friday, March 04, 2022

### Excel Vector Calculator - Be Careful How You Use It

I was asked to show this video to students on how to set up their own vector calculator using Excel. The calculator gives you the ability to find the sum of vectors just by entering each vector's magnitude and direction.

Is it useful? Sure it is, but this is where if you don't know what is going on, you may be using it incorrectly! I have a couple of examples to show that.

After you have set up the calculator using the example shown in the video, enter these:

Vector A: Mag=9.8; Ref. Angle=114

Vector B: Mag=16.5; Ref. Angle= -104

Vector C: Mag=11; Ref. Angle=180

If you have set up the calculator correctly, you will get the resultant vector having a magnitude of 20.2 and a direction of 20.4 degrees.

If you don't know any better and I ask you to sketch out the direction of this vector, you would have drawn an arrow that is pointing in the first quadrant of a Cartesian coordinate system, which would be WRONG! In fact, most of my students would do that. It is a natural and automatic tendency to do so since angles are measured counter clockwise relative to the positive x-axis.

If you do a quick sketch and do a "tip-to-tail" vector addition, you will end up with a vector that is actually pointing in the 3rd quadrant! In fact, the true angular direction for this vector is 200.4 degrees (180 + 20.4, the latter is the angle found from the calculator).

The reason for this is that in calculating the angle, one is dividing the y-component by the x-component. This vector has both components being negative and so the division produces a positive value, producing a positive angle. But this angle given by the calculator, if one were to sketch out the vector, is the angle measured from the NEGATIVE x-axis, not the standard positive x-axis. If one remembers lessons from trigonometry, it is why the value of the tangent of an angle is positive in both the 1st and 3rd quadrant.

So the angle given is "correct" if one knows where it is measured from.

Here's another example to try:

Vector A: Mag=12.7; Ref. Angle=45

Vector B: Mag=19.2; Ref. Angle= -171

Entering this into the calculator, you get the resultant vector having a magnitude of 11.7 and angular direction of -30.9 degrees.

Once again, if you simply go by what you get, the tendency here is to think that the vector is in the 4th quadrant, because a negative angle means that it is an angle measured from the positive x-axis but going clockwise.

This is wrong.

The vector is actually in the 2nd quadrant. A simple sketch to do the vector addition will confirm that. The angle "-30.9 degrees" is actually an angle measured clockwise from the NEGATIVE x-axis. For this vector, the x-component of the resultant is negative, and thus, the ratio of the y-component to the x-component is negative, resulting in a negative value of the tangent and the angle. Once again, from trigonometric lesson, the tangent of an angle is negative in the 2nd and 4th quadrant.

What this all means is that a positive angle value is not unique - the vector could be in the 1st or 3rd quadrant - while a negative angle value is also not unique - the vector could be in the 2nd of 4th quadrant. Either do a quick sketch to do vector addition, or look at the sign of the resulting components.

There are two important lessons here. First is that one must know what the numbers mean. Using them blindly without understanding how they come about is risky and may result in the wrong conclusion. Secondly, for this exercise, there is no substitute for doing a sketch and knowing how vectors add. A simple sketch will provide an important sanity check that your conclusion about the vector direction is not wrong.

While this video and the setting up of the calculator is useful, the producer did not go far enough to demonstrate the possible pitfalls in using it blindly. There should have been examples involving what I had presented to tell the viewers what they should be careful about. I just wonder how many people had used this and interpreted their results incorrectly.

Zz.

## Tuesday, March 01, 2022

### Whatever Happened To The LHC-Will-Destroy-The-World Nutcases?

Remember way back when the LHC was about to start up and a couple of nutcases decided to file a lawsuit in the US to stop it? If you missed the fun, read a couple of my earlier posts here and here, and the dismissal of the lawsuit here.

So now that the LHC has run for many years, had gone through an upgrade, and will probably continue to do so for the next few years, what do these wackos have to say for themselves? I know that going back and asking them will probably be fruitless because we are giving them more airtime than they deserve, but I'm always curious to see how someone like this react to the clear demonstration of how wrong he is.

But then again, if something like the Jan 6th insurrection can be called a "legitimate political discourse" despite the most obvious evidence, then there's no convincing some people of how wrong they are.

Zz.