As I tutor physics, I often find students who are puzzled by experiments they were exposed to in class. Today’s she found herself confused by precisely what went on during a classic “electroscope” lab. She could describe the observations but she said she knew she didn’t understand precisely what was going on with the electron flow.
I knew I could explain the results to her, try to sketching things out and so on. Lucky for me and her, I was aware of something even better. A great video on inductive charging of an electroscope. Here it is:
Now I know some of you are going to say, “How can that be great? The scope is just an ugly bent hanger! There aren’t any equations. It isn’t cool, cutting edge. That would never make it into a NOVA like special. Blah. Blah.”
But I’ve shown this to several students who were puzzled about electroscopes, and it really gave them an “A Ha!” and an “Oh wow! Now I get it.” Also: the video is short, doesn’t digress into lots of other things; the electroscope may not be pretty but it is real (not a cartoon). The student did make me stop at one point where she was confused and I could show her precisely how the flow of electrons was illustrated by the guy’s super-imposed +/- signs and we could scroll back a bit.
Students always love the good videos if seen at just the right time.
Many ask how I find the ones I do find because they report that they sometimes look and hunting for useful videos — sometimes they hunt because their teacher suggests there are good ones “out there” without pointing to anything in particular. But they find hunting is just a time sink that never results in good ones.
In fact today’s student asked me how I find good ones and I told her: I spent quite a bit of time looking for the ones that are good and beyond that, I know what it is the teacher is trying to get them to grasp. So, I look for videos that focus on those topics. I would never tell a student who is trying to learn to actually look for a video themselves. It takes a long time to find the ones that actually help on the topic the student is trying to better understand in the time frame they need for their course.
I have a few more great videos I’ve found and I’ll be showing them from time to time. (There’s a great one out there showing standing waves and a few fun ones on the Doppler effect.) If anyone happens to know of great physics videos, I’d love to see links.
Mind you: what you think is “great” may not be what I think is great. 🙂 For helping kids with a concept videos generally need to be less than 10 minutes; ideally, it should be less than 5 minutes long. Half-hour or hour-long videos may be good lecture replacements but they are rarely (as in almost never) helpful to a student who has a specific question about a concept they are trying to master. That said: there are some good “lecture replacement” videos. It’s just that students rarely need them– they already have lectures or classroom activities. But if you think you’ve found a great video of any sort, let me know.
Is this an open thread: Yep. 🙂
Update 1/27/2017: For convenience, I’m moving political discussion to the following post which describes a Trump strategy on the ACE.
Several days ago Lucia mentioned her physics teaching, which so happens to be the same week my sophomore son has to schedule his classes for next year. He wants to schedule AP Physics 1 for himself. I am a little afraid that it may be difficult and time-consuming for him and that maybe he should take what I will call “moderate” physics, which is not as demanding as AP Physics.
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My son is good in science (scored in top 2% in Ohio last year as well as top 6% in math), but I am afraid that AP Physics may interfere with his other subjects and projects. He doesn’t want to major in a science field in college. This year he had a difficult chemistry course and started slowly and barely got an A. He also had some difficulties in the beginning with second year Algebra and got a B in the first quarter and an A in second quarter, which averaged out to a B for the first semester. (The only B he has gotten in high school)
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My basic question is whether it is worth risking getting a “B” in AP Physics when he could take the “moderate” physics and almost certainly get an “A” Of course, learning the subject matter is very important (Physics is both fun and important), but if he really isn’t going to use the physics later in life maybe the moderate physics is better. (For instance, I have never used Algebra 2 in my adult life) A big part of my motivation here is qualifying my son for a merit based scholarship. Not only would he almost certainly get an A in the moderate physics, it would help insure that he gets “A”s in other difficult subjects — He will be taking AP American History, for instance. I am afraid that lowering his grade average may make it harder to get a merit-based scholarship. Any thoughts or advice would be appreciated.
JD
See that’s interesting. I’d thought induction had to involve waves, or changing voltages – I thought that’s what it meant. Like explained here. I didn’t realize that this is also inductive charging.
I’m trying to figure out how to modify the working definition I have in my mind now for [edit: the word] ‘inductive’ to cover both cases..
The definition here is how I’m used to thinking of it:
It’s not obvious to me how this applies to the example in the main post. What do you think Lucia, am I making simple things complicated for myself? (rhetorical invitation to remark in whatever way)
I guess whenever electromagnetic fields rearrange electrons in a conductor we can call that ‘induction’, is that the short answer? Real question.
Mark,
No. You’re just thinking the term “induction” is narrow. The word “induction” is more generic. Outside physics it can mean “the process or action of bringing about or giving rise to something.”
It happens to be the case that “charge by induction” and “electromagnetic induction” are ways to “bring about something in some way”, but the thing brought about is different. In current, “accumulation of charge” is induced and it occurs by a current being “induced” by contact to a ground– and obviously, some emf is applied. (The emf is applied by the difference in charge between the charged rod and the ground.)
This is not “electromagnetic” induction which would be induction caused by a conductor moving relative to a magnetic field.
Bear in mind, once one is discussing “electromagentic induction”, they tend to avoid discussing other induction and often drop the adjective. But that doesn’t make “charge by induction” mean someone means “by electromagnetic induction”. The two things are different.
I should add: no high school student will be confused by this use of “induction” at this point because the ‘electroscope’ stuff is done long before they cover “electromagnetic induction”. Those in conceptual physics don’t cover the latter at all. AP Physics C covers it and AP Physics 2 covers it. “Traditional” physics generally covers it a bit.
Ahh! So what’s going on in the example in the video is in fact a different thing.
Thanks Lucia. I was about to injure myself trying to somehow make those the same thing in my mind. 🙂
Nope. Not the same thing. They just share the word induction.
JD Ohio,
There isn’t much harm in taking it– he’ll get practice taking tests. But he should be aware pass rate for AP Physics 1 test is very low.
https://www.totalregistration.net/AP-Exam-Registration-Service/2016-AP-Exam-Score-Distributions.php
5 4 3 2 1
Physics 1 4.3% 13.6% 21.3% 30.7% 30.1% June 15
If he does want to try, he should buy an AP physics 1 prep book (used is fine) and make sure the topics he covered match the AP Physics 1 curriculum. Often “regular” physics contains some topics not on AP Phys 1 (it’s in AP phys 2) but skips some on AP Phys 1. This makes it very challenging for kids who think that because they did very well in their classes, they might be able to take AP Phys 1.)
For example: Kids in HInsdale Central high school “regular” physics has very little to no “rotational dynamics” which is on the AP 1 test. Specifically, they never cover “moment of inertia” or T=Iα. On the other hand, the Hinsdale Central kids do have “optics”, “sound”, “magnetism” and even and “electro-magnetic induction” which is not on the AP 1 test. (FWIW: I think often “traditional” physics is just as hard as AP1. BUT it doesn’t prepare the kids for the AP 1 test.)
Kids at Metea/Nequa in Naperville don’t cover “waves”– which is on the AP 1 test and similarly no rotational dynamics. But once again: they do cover some magnetism. My guess is Wheaton/Warrenville is similar.
So: get the syllabus and we can advise your son.
If your son’s teacher has a syllabus they are willing to share, I can compare for you and tell you whether the topics match.
Oh… I think I misunderstood. I thought he wanted to take the test even though he took “traditional” physics.
Actually: if you are worried about him taking AP I physics, I would recommend he do some not very stressful summer work. It’s not necessarily a harder class than Traditional physics. But ideally, he gets a 5 on the test. That way he gets college credit and if he’s not going into the sciences, he might be sort of done with physics. 🙂
I can point to some summer stuff that’s not too stressful. (There’s a mooc. I also have some self test stuff he can do pretty much for free– all at a level that’s easier than AP 1.)
If he grows to love physics, he can still take more.
There are tons of “conceptual” physics things he can go through on his own in the summer that will make AP Physics easier for him.
JD–
This MOOC is good for the summer before AP physics:
https://www.udacity.com/course/intro-to-physics–ph100
Lucia: “Nope. Not the same thing. They just share the word induction.”
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The use of confusing “technical” terms is something on my mind now. I rooted my Android tablet about 2 weeks ago, and once you learn how to do it, it takes about 5 minutes. However, wading through the confusing terminology is very difficult and resulted in me using about 100 hours to get it done over several months. (Pure stubbornness and bullheadedness on my part to spend so much time on this task.)
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For instance, what most people would call installing a program on a Windows computer is called “flashing” when you are rooting. The program that must be pre-installed before you can “flash” [install] what most computer people would call an operating system is called a “recovery.” When you start out, you feel you are entering a whole different world, but it really isn’t that different from Windows computer work. You back up your stuff and then install.
An example of a needlessly confusing legal term is “inchoate”, which fundamentally means unripened. An attorney I know used the term inchoate without explaining it while giving a talk to a group of lay people. I am sure nobody had any idea what she was talking about.
JD
JD Ohio
JD,
something which oozed out of the fence thing today was the notion that Mexico does have an interest in blocking the migration. If the migration is blocked all the folks who come up from their south with hopes of winding up in US will quit. Assumption is they’ll stay home rather than stay in Mexico.
Trump thinks a lot of these guys are banditos and Mexico should feel better off without them. Not to mention possibility that better fence might attenuate northward drug flow and southward weapon flow which also should be good for Mexico – so if you believe all that, Mexico should pitch in.
I wonder if I can get a job in the new administration explaining the unexplainable.
JD Ohio
Well… yeah. And you’d think Trump could privately discuss the fact that there was no need for a meeting unless building was a team project that– for some reason– Mexico wanted enough to pay for. In fact, as far as I am aware, Mexico doesn’t want it at all. There’s no conceivable reason why they would either want to (a) build it, (b) cooperate with getting it built or (c) paying for it. Of course they cancelled going to a meeting about this issue.
Not high-school physics, but this is a good short video on special relativity.
Here’s a short one on centripetal force .
RB.
High school students do do special relativity. Generally only those taking the lowest level, no math, physics (i.e. Conceptual Physics). Because it’s mathematically easier than things like rotational dynamics, multi-dimensional mechanics, magnetism or electrodynamics and so on.
Those in traditional physics or AP Physics C don’t take it. Though those in AP Physics 2 do take it– but very few schools do AP Physics 2.
Ooohhh! That’s a great centripetal force one!
That’s true, mathematically it is fairly simple. I probably have a few other videos I’ve emailed myself in the past which I could find if I had been better organized 🙂
RB,
Moodle has “categories” on the back side. The “top” physics category is accessible from all “courses” and I’m putting links to the good videos in there. Then I can add them to “sections” on the appropriate topic at any level of “course”.
You have to understand a bit about moodle to get what I”m doing. But mostly, the really good videos tend to be useful both to students in “conceptual” physics and in the AP courses or the entry level college course. What then happens is the “more advanced” classes apply the exact same conceptconcept at first. Once the get that, the already understand the math– which they got used to in their math class. So, many of the best videos are the same for nearly everyone.
But oddly– to many– it turns out special relativity as covered in high school fall is category (1) and so is nearly always covered in “Conceptual Physics” but often (but not always) skipped in classes with more math!
It’s electrostatic induction rather than electromagnetic induction. Electrostatic induction is used to power Van de Graaf generators.
That it is! Thanks DeWitt.
I saw this one when I was kid back in the early 70’s, can’t find the original though.
Fission / Ping Pong balls and mouse traps.
https://www.youtube.com/watch?v=XIvHd76EdQ4
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Here is the proper version, using 2 balls per trap. At 15:00
https://www.downlossless.net/videos/the-atom-a-closer-look-1980-educational-disney-film-q5k5e5f65675a6c5c4x4o5.html
Well, my take is this. Pretty much everything that has been written about “electromagnetic induction” is mumbo-jumbo jibber-jabber. Also lines of force. Maxwell’s equations contain all you need to know about the workings of the electromagnetic field, at least in free space. Or you could just read and digest volume 2 of the Feynman lectures on physics.
winston,
Feyman’s lectures may be all one truly need to know. But it is best to be aware that he assumed those taking his introductory class has learned some physics in high school. In his introduction he writes
So I would suggest the even he would never suggest that his lectures were a replacement for high school physics. His lecture audience consisted of kids who took physics in high school and who also were admitted to CalTech. This means they actually likely had already learned much of what the high school students are being first exposed to before sitting in that lecture.
Also: pretty much no one uses Feynman lectures to teach.
His own diagnosis suggests he doesn’t think his lectures are particularly outstanding in EM.
One thing I definitely agree with him on:
and later on
So often I read physicists moaning and wailing that kids don’t do “quantum” soon enough. And that’s some how a problem. Well that doesn’t seem to be what Feynman thought.
I was also struck by this
Well… of course that is tutoring provided the student has a disposition to ask questions and the tutor encourages that. Tutoring doesn’t always work out that way because (understandably) students are very focused on completing assignments their teacher gave them. (And they do need assignments and would need them even if one thought oneself acting as their Leonardo da Vinci to the Di Medici kids.)
lucia,
As someone who was a freshman at Caltech starting in 1961 when Feynman was the freshman and sophomore physics lecturer, I’ll second that. Most of us didn’t have the math background for QM, unless you had the mathematical intuition of a Feynman.
Tom Scharf (Comment #157948):
I recall simulating the mousetrap/pingpong balls back in high school. [This would have been in BASIC on a time-shared PDP-8.] My math teacher described the sytem and I wrote a short program. I vaguely remember producing a plot of the number of active balls at each time step. I didn’t think of it as a model of a nuclear chain reaction, but that makes sense.
First time I went beyond writing game programs: moon landers, poker, slot machine, etc.
P.S. For fun, I googled that teacher, who was just out of college at that time — evidently her first position. Turns out she ended up as a professor of math & computer science, apparently just retired in 2015.
Max_OK,
You bringing up the relativity video and max bringing up Feynman lectures makes me think it would be interesting to collect together data on which topics high school physics teachers do cover and in which classes at their school. Sort of a checklist with columns for topics and rows for classes or vice versa. Topics can be:
Newton’s 1st-3rd law.
Types of forces:
F=mg.
Static & Dynamic friction.
Tension.
Universal Gravitation.
Work-Energy: Sub
Energy only.
Work & Energy.
Cons. Momentum.
Impact Momentum.
.
.
.
Special relativity
And so on.
In principle, I could ask all the teachers. In practice, the two times I have contacted teachers of students I tutor they seem very reluctant to give out syllabus or answer questions like “what will you be covering next semester”? (By reluctant, I mean things like this: One would answer all questions of like “Do you have a syllabus?” or “For example, will you be covering Coulomb’s law?” and so on with “What do you mean?” and another would answer things like “Ask the student what we are covering?” I was mystified how the answer to a question like “Will you be covering Coulomb’s law?” could be “what do you mean?” or how the teacher could think asking the student would help me know what would be covered next semester– or even next week. Heck, struggling students often don’t know how to describe what was covered last week. That’s why they are struggling!)
But anyway, I suspect it would be hard to get together a list of “what teachers actually cover.” I do discover this based on students I tutor.
For example: So far, one of the classes here in Lisle has covered 1&2 D linear kinematics, Newton’s 1-3 with various specific forces, and some conservation of momentum. As far as I can tell, they have not covered impulse-momentum— but they may have. (The kids had bridge building and egg drop early, so I don’t know what other assignment or quiz topics were.) I can’t reveal seeing any torque, circular motion, universal gravitation or anything to do with E or M from the Lisle students. It’s v_e_r_y s_l_o_w. (I don’t know if there is a faster paced high school class as well– but their physics seems r_e_a_l_l_y s_l_o_w. Oddly, this does not necessarily decrease the difficulty for them.)
I know that in Hinsdale-Traditional Physics they would have had everything the Lisle kids had plus Impulse-Momentum (I=Δp), circular motion, universal gravitation. I’m trying to remember if they have torque-statics in the fall or spring. Hinsdale-Traditional doesn’t do rotational dynamics Ï„=Iα ever. They start EM, do geometric optics-light-color and waves-sound in the spring. (No harmonic motion. No relativity. No thermo, heat transfer, elasticity of materials. Mysteriously, their teacher tortures them with trivial minutae like the colors system used to indicate resistance on resistors. But they do not cover the fundamental concept of resistivity– R=ÏA/L. It strikes me as a waste that they are memorizing stupid stuff like ‘red means’ but don’t learn that resistivity, Ï, is a property of a material which relates to R is a certain way. But… oh. well. )
Benet Conceptual physics covers Newtons 1-3 & Kinematics w/o any trig, but then covers a huge number of topic w/o any trig or significant geometric complexity. (So, for example, they do cover special relativity, elasticity of materials, expansion of solids with heat, Pascal’s law and so on. If it’s a “one equation” thing, they pretty much do it!)