The immediate follow-up to the Electric Magnetism activity is the Magnetic Electricity activity. As one might expect, Electric Magnetism explored the ability to produce magnetic fields using electric currents. Magnetic Electricity moves on to using magnetic fields to produce electric currents, with an emphasis on "moves".
Induced current and turning motors into generators are at play in this one.
Student Document (Google Docs) Observations HTML Export | Movie (link embedded in Student Document) Answer Key (Google Docs)
Media links are included in the student document. The HTML export is preferred. The movie export is available for use on devices that struggle with the HTML export.
With Ørsted's Discovery, we established that electric currents are surrounded by magnetic fields. In this activity, we extend that to the design of electromagnets and motors. In our traditional, In-Person Learning electricity and magnetism sequence, we would have used our Genecon hand-crank generators to power electric circuits. In short, we would have been familiar with their utility as generators. Here we turn the tables so that the Genecons become motors.
This one is also a bit fiddly in class: St. Louis motors are great, but students will discover all the ways they can go wrong. I don't think that's a bad thing, but there is frustration in the room. You lose that in the RT;DL version. You lose a lot in most RT;DL activities.
But it's a nice sequence of observations, building on Ørsted's Discovery and setting up the next activity: Magnetic Electricity.
Observations (HTML Export | Movie Export linked in Student Document)
Answer Key (Google Docs)
Media links are included in the student document. The HTML export is preferred. The movie export is available for use on devices that struggle with the HTML export.
Enjoy my lack of professional production sets, lighting, and technique. These are all shot in my classroom using classroom apparatus and lighting options, and shot on my iPhone 8. Presentations are created in Apple Keynote and exported as HTML and exported as a movie.
This activity explores the magnetic field around a current-carrying wire: Ørsted's Discovery. It's a bit fiddly when we do it in the classroom. The compasses can be thrown off by steel spines and/or leg plates in the tables. To be honest, I've seen compass behavior I cannot explain in my classroom. Perhaps strange things happen to our compasses while they're stored during the off-season. They are stored in proximity to bar magnets.
In any case, I got passably reasonable behavior from my compasses as I recorded the videos for the RT;DL observations of this activity.
Because I was recording the observations on behalf of the students, I provided them to the students in a disorganized way. Students would need to match the randomly sequenced observations with the called-for observations in the activity instructions. It's RT;DL ... you do what you can.
The HTML reports are preferred; the movie exports are provided for users whose devices struggle with the HTML exports. Links to all media are embedded in the student document.
Apologies for any clumsiness that comes through in the videos. The physical geometry required for recording these events is awkward, and I really didn't invest much time in rehearsal. I was happy to get decent light on my subjects.
This activity shows a magnetic field projectual being used to reveal the magnetic field around various configurations of bar magnets. As with all RT;DLs, this activity began as an in-class lab and has been retooled for online delivery.
I will confess that I find watching iron filings slowly align with magnetic fields on a large screen to be calmingly satisfying. I suppose it's my ASMR.
When we study magnetism, we learn that certain animals have awareness of magnetic fields and can use it for navigation. Certain birds are known to have magnetite in their skulls. Here's a nice update of recent findings regarding magnetoception in birds.
Humans do not seem to have this capability. But that doesn't mean our brains are entirely oblivious to magnetic fields.
Veritasium's Derek Muller dons a sensor-laden shower cap of science to test his brain's awareness of the magnetic field it's immersed in. Could it be that the brain senses magnetic fields but doesn't share the information with our consciousness? Take a look.
Over the course of geologic time, magnetic north wanders like the oft-maligned "drunken sailor". And it reverses polarity on a not-entirely-stochastic basis. It seems the pole is on the move again—with faster than normal speed—and models will need to be updated to keep pace.
There comes an awkward moment in my AP Physics 2 course when we arrive at the topic of electromagnetism. Students enrolled in Physics last year studied magnetism in some depth, with a robust qualitative laboratory component. Students enrolled in AP Physics 1 did not hear the term "magnetic" in class at all: there is no magnetism in AP1.
So I segregate my AP2 charges by which course they had las year. The former AP1s move quickly through the Physics course material while the former Physics students get some enrichment by way of The Mechanical Universe, Conceptual Physics Alive, and Nova. Eventually we reunite and move into deeper issues of electromagnetism and induction, ending up at Faraday's Law.
The Nova episode is S31E07, "Magnetic Storm," concerning the changing nature of Earth's magnetic field. [Warning: do not make a drinking game out of each time a thunderbolt sound effect is deployed—you will not make it to the end.]
In developing a video question set to accompany the episode, I noticed that a pop song was featured heavily throughout the episode. A bit unusual for Nova in my experience. The end credits included the name of the artist but not much else. It was enough to track down the... track.
It's Judith Edelman's "Magnetic" from the 2009 Thirty One Tigers release, Clear Glass Jar, available on iTunes, Amazon, and wherever fine music is sold. Someone commented that Edelman's "Magnetic" is to electromagnetism what Don McLean's "Vincent" was to the art of van Gogh. You be the judge!
It's the buzz when I'm full Of your sweet magnetic pull It's the tug that I crave It's how opposites behave Is electricity all there is to you and me? In the fields, in the fields Where the static is revealed If the north isn't true Will I lose my way to you? Is electricity all there is to you and me? What's gonna happen when the magnetism fades? Will we burn up one bright day? Will the aurora borealis give us one last show? You can't leave love to science when you go. In the deep molten heart Where these strange attractions start If we are passionate Will this rock remember it? Is electricity all there is to you and me? What's gonna happen when the magnetism fades? Will we burn up one bright day? Will the aurora borealis give us one last show? You can't leave love to science when you go. What's gonna happen when the magnetism fades? Will we burn up one bright day? Will the aurora borealis give us one last show? You can't leave love to science when you go. It's the buzz when I'm full Of your sweet magnetic pull
Bree Barnett Dreyfuss recently pointed out this amusing feat of daring-do to me. Take a look at this breathless tale of magnetically-braked cordless bungee jumping.
As a veteran of bungee jumping, I was thrown off by the use of the term "wire" in this context. "Rope" or "cord" are common terms used to reference the bungee, but not "wire". The term is obscured a bit via use of a second language (translation issues?). But by the end, the need for the use of that specific word is clear.
In any case, it seems not everybody picked up on the clues that the whole spot was a spoof. That's what Snopes is for: Bungee Leap of Faith.
But magnetic braking is far from unheard-of. Engineered use of eddy currents/Lenz's law has been deployed on a large scale for the benefit of thrill-seekers at amusement parks for years.
It seems the Ikea production team took some cues from this classic Mercedes Benz barrel roll fake. A team of nervous scientists working furiously toward a singular moment. An accomplished daredevil willing to risk life and limb for the sake of science and adventure. This one really goes over the top (!) in terms of cinematography and soundtrack. I like this version, which includes a wink at the end.
At the 2017 Summer AAPT meeting in Sacramento Arbor Scientific had a booth in the exhibit hall showing off all their great demos. This Electricity & Magnetism Light Bulb demo caught my eye. It involves an incandescent light bulb with a long loose filament that can be turned on using AC or DC current. While on, a strong neodymium magnet is brought near the bulb with different results depending on the setting. When on DC the filament moves towards one pole of the magnet and away from the other. When on AC the filament vibrates when either pole of the magnet is brought close to it. I wanted one, but the reasonable price was still hard to manage for a once a year demo.
Last year I wanted to show my Conceptual Physics students a working dimmer switch and a simple light bulb. My retired father-in-law made me a self contained box with a dimmer switch and an incandescent bulb:
While shifting equipment around in my room I came across it again while my magnet cabinet was also open. As I recalled the Arbor Scientific demo I thought, "I wonder if...." and grabbed my biggest neodymium magnet.
With the light bulb on dim so that the filament can be easily seen I moved the magnet close to the bulb. Since my bulb's filament wasn't as long as the one in Arbor Scientific's demo you don't see as much movement but it is vibrating! The second video is easier to see the motion.
Now I know that my simple demo has a dual purpose and can be used in my current electricity unit and come back in my electromagnetism unit!
Every year, for as long as I can remember, I've shown a clip from the British show Brainiacthat makes a giant pendulum mirroring the in-class bowling ball demo. My downloaded copy is grainy and pixelated so I decided to try and find a better version. I downloaded one Brainiac episode (Season 1, episode 3) with the intention of editing it down to the 4 minutes or so that I wanted. I ended up watching the whole 40 minute episode and editing out six clips to use in my classroom. Not too shabby for some fun TV time.
Conservation of Energy and a giant pendulum:
Well explained and stands alone well.
Oil Slip & Slide:
Even really slippery surfaces have a coefficient of friction that slows down moving objects. You could have students estimate it using the values given in the clip.
LN2 filled water bottle:
Quick example of pressure, boiling and of course liguid nitrogen.
Does a duck's quack echo?
Sometimes students just won't believe you unless they see it for themselves. Or in this case hear it.
Don't microwave a CD:
#ThingsThatShouldGoWithoutSaying
Playground G forces:
Brainiacs (the volunteers and staff that put on the science of the show) try to get the most G forces possible out of a playground merry-go-round. You could get more but they are limited by human power.
Iron in cereal:
This is an easy demo to do in the classroom but it does take some prep, the right cereal, etc. This is a super short clip that demonstrates it if you don't have the time.
Now I want to watch more of it. Besides the energy pendulum the only other clip I have seen prior to this was another all time favorite, "The Electric Fence." It is pretty much all the things you wish you could do in your classroom but couldn't:
Update: For an exhaustive video demo lesson on the Brainiacs: Electric Fence clip, see this old Blog of Phyz post:
Last weekend I presented at the Exploratorium's 4th Annual NGSS STEM Conference "Making Science Count: Integrating Math into an NGSS Classroom." I presented a few inverse and inverse square relationships participants explored using hands on experiments. One of them was to investigate the relationship between the strength of a magnetic field and the distance to the object.
Thanks to sponsors, participants were able to go home with their own "cow magnet" (if you don't know why they are called that read about Hardware Disease). While preparing for the workshop that morning senior scientist and staff physicist Paul Doherty cautioned me that while I would expect cow magnets to be dipoles they could be tripoles. After he check with magnetic viewing film it turned out they were quadpoles. And that can complicate an experiment.
Workshop participants either borrowed my Vernier Magnetic Field Sensor or used the magnetometer on the Physics Toolbox app during the workshop. When I was preparing for the workshop I found that this could be an inverse square or an inverse cubed relationship depending on the physical dimensions of the magnet. Given the orientation of these quadpole magnets if you rotated the cow magnet at all as it approached the sensor the polarity could change.
1. Asking questions (for science) and defining problems (for engineering)
Below is a video using a dipole donut magnet, a dipole cow magnet and a quadpole cow magnet that models what I would expect students to see.
I investigated further using my Vernier Magnetic Field Sensor once I got back to school. Below is a graph made by starting the sensor perpendicular to one end of the cow magnet and then moving up the length of the cow magnet to the other end. I put a pencil in between the cow magnet and the sensor to maintain the same distance between them.
On the left, the red line was made using a dipole cow magnet and the blue by the quadpole magnet. In this case they are similar and one might conclude that they are both dipoles. (Differences in slope are due to the sensor's speed.) On the right, the red line is the same, made with the dipole magnet. The orange and green were both made with the quadpole magnet. When the green line was made the magnet must not have had a pole directly facing the magnetic field sensor.
I also pointed the sensor at the end of the cow magnet and rolled it along the table, keeping the sensor from rolling and at the same distance away. I tried it twice with the quadpole magnet, creating the green and purple lines in the middle. This was harder to keep steady but you can see the polarity switch as the lines pass the time axis. Repeating the experiment with the dipole created the brown line at the top of the graph. For the dipole rolling it made no difference in the polarity strength or direction.
So what can you do with a pesky quadpole cow magnet? Why, confuse your students of course! I plan to hand groups of students one dipole and one quadpole cow magnet and ask them to determine the number of poles on each. If they are lucky they will get a compass and/ or viewing film. Otherwise having two magnets should be interesting enough. If you're keeping track of the NGSS Science & Engineering Practices, such an investigation could lead to quite a few of them in one lesson:
2. Developing and using models [of thinking]
3. Planning and carrying out investigations
4. Analyzing and interpreting data
5. Using mathematics and computational thinking
6. Constructing explanations (for science) and designing solutions (for engineering)
7. Engaging in argument from evidence
8. Obtaining, evaluating, and communicating information
In late May, 2008, a set of videos were uploaded to YouTube that were soon to go viral. Each one appeared to be a handheld video capture of a group of enthusiastic twenty-somethings conducting a home-made experiment to see if cell phones could be used to pop popcorn.
The cell phones are arranged to focus their energy at the few kernels of popcorn. The phones are then simultaneously called, apparently by a second set of cell phones these casual friends happened to have on hand. After the phones begin to rattle and ring—but before they go silently to voicemail—pop go the kernels! Take a look.
My award for the greatest display of enthusiasm goes to the Japanese video. The notion of popping popcorn with cell phone radiation swept the Internet's imagination, and people tried to repeat the experiment around the world.
They all failed. Without exception. But it had to be real, it was a video on the Internet! (Ah, the innocence of 2008.) Speculation arose that specific cell phone brands had to be used. Some thought there was a hidden heating element at work. Others correctly deduced video editing shenanigans.
The complete worldwide failure among those who tried to reproduce the demonstration speaks nicely to a key principle in science: reproducibility.
It was later revealed that the videos were a stealth marketing campaign produced by a manufacturer of Bluetooth headsets. The president of that company denied that the intent was to suggest that it might be smart to use a headset and keep the microwave cooker of a cell phone away from your brain. (Medical evidence suggesting cell phones cook brains is not compelling.)
Eventually, the Internet moved on to the next viral video. Was it Microsoft's Megawhoosh featuring even more bad physics? Mythbusters didn't even bother with cell phone popcorn, but Brainiac Science Abuse did.
It's worth remembering such hoaxes. Looking back, there are easy-to-spot tell-tale signs of hoaxterism. So of course, I wrote a quick YouTube Skepticism lesson to probe this set of videos and its raison d'être.
YouTube Skepticism: Pop Corn with Cell Phones @ Teachers Pay Teachers The larger point isn't that this particular hoax needs to be debunked but rather that there will always be a next one. If students can recognize fakery in classic hoaxes, they'll be prepared to cast doubt on new ones.
Hoaxers are nothing if not consummate recyclers. Copper bracelets become magnetic bracelets become hologram bracelets become aqueous titanium-infused necklaces and so on and so on.
Join any teacher conversation group and you will inevitably hear one or more of the following: "Kids these days are so lazy!" "They can't get off their phones!" "Kids today can't THINK!" There are people on both sides of this argument, saying kids these days are or are not lazy. There has been a bit more research about the critical thinking component; I like this article from The Huffington Postwhich mentions quite a bit of that research. There is a well documented connection between the ability to argue and true understanding of the material. Being able to think about a situation from more than one perspective allows students to argue effectively and respectfully. That's probably why one of the new Next Generation Science Standards Science & Engineering Practices is "Engaging in Argument from Evidence." The 9-12 portion includes:
Compare and evaluate competing arguments or design solutions in light of currently accepted explanations, new evidence, limitations (e.g., trade-offs), constraints, and ethical issues.
Evaluate the claims, evidence, and/or reasoning behind currently accepted explanations or solutions to determine the merits of arguments.
Respectfully provide and/or receive critiques on scientific arguments by probing reasoning and evidence and challenging ideas and conclusions, responding thoughtfully to diverse perspectives, and determining what additional information is required to resolve contradictions.
Construct, use, and/or present an oral and written argument or counter-arguments based on data and evidence.
Make and defend a claim based on evidence about the natural world or the effectiveness of a design solution that reflects scientific knowledge, and student-generated evidence.
Evaluate competing design solutions to a real-world problem based on scientific ideas and principles, empirical evidence, and logical arguments regarding relevant factors (e.g. economic, societal, environmental, ethical considerations).
If you look at that list in its entirety you might, (okay, you will) get overwhelmed. But don't be! Try looking at just one or two at a time and they are much more attainable. For instance, my 5 year old completed most of "Construct, use, and/or present an oral and written argument or counter-arguments based on data and evidence" the other day. And that's not bragging, allow me to explain:
My kids love magnets and have this mixed set of sticks with small neodymium magnets and ball bearings. In typical kid fashion whichever piece my 5 year old daughter had my 2 year old son wanted and vice versa. He was usually color oriented; my daughter was more focused on particular pieces of their mixed set. I finally asked her why and she said, "These yellow ones are stronger than those." I asked her how she knew and she said "It just feels stronger." Sometimes I can't help that I'm a teacher, and we set up an experiment. I had her collect all the different kinds of magnetic sticks she could find (green, red and yellow below) and a ball bearing. We drew two lines on a pieces of scratch paper and put the ball bearing on one. We started with one magnet on the second line and I had her slowly move it towards the ball bearing on the other. At some point the magnet got close enough to attract the loose ball bearing. We marked that position and repeated it for all the different kinds of magnetic sticks. There was one trial during which the ball bearing moved (which is also when it got wet) and she said, "Mom, that doesn't count, it moved." *so proud*
In the end we got this simple set of data that showed how the magnetic force varied with each different type of magnetic stick. I was surprised that the results were fairly consistent. I asked her "Which magnet was strongest?" and she answered "The red one, because it pulled the ball more, from farther, the others had to get closer, so they aren't as strong. I thought it was the yellow but its not." So she constructed an argument for the phenomenon she was seeing based on the data we collected. She accepted a result different from her initial opinion based on her experiment. You might even count her description to me as a presentation of her argument! Not bad considering it all stemmed from a sibling squabble. How does this apply to your classroom? Focus on what your students know based on what they have done. Ask them to explain what they are seeing, have students discuss their findings with each other. Bottom line, "kids today" can think and critically think with your help.
Its mesmerizing. This is quite the set-up and while quite complex can be used to discuss a variety of things with students. As the video description mentions its not quite a Rube Goldberg machine because its done in several takes even one "scene" has quite a few energy transfers and they do begin with a single marble starting. I kind of want to just play it over and over again for my students and see what they notice.
As a child of the ’80s, I saw Short Circuit more times than I can count. To this day whenever I take something apart I hear the terrified Number 5 yelling, "Disassemble?! No!!" as he realizes what it would mean for him. But I still take things apart, because it is fun.
There have been many things I've collected (okay, maybe call it hoarded) over the years for use in my classroom. Some I have specific and immediate uses for .... some not so much. I still have part of the framing from a holiday light lawn sculpture of a snowman that I just know will be perfect for something, someday.
I finally got the time this year to disassemble an old toaster, hair dryer and space heater. I reference these appliances when I teach electricity as a practical example of the conversion of electric energy to thermal energy. By the time we get to that, students have often had personal experience with that conversion when they leave their circuits on too long and touch hot resistors.
Even though we've talked about the dissipation of heat from electrical circuits I don't think my students believed me until they saw all those coils of wire. It was a simple thing to take them apart (they weren't working anyway) but many of my students were just in awe of seeing the inside of something. Little do they know they get to do it next week.
Now that our current electricity unit has come and gone we have moved on to electromagnetism. I have my students make a speaker out of paper using a paper template I made (pdf or google doc), a doughnut magnet and a coil of magnetic wire. Its a simple build based on Modesto Tamez's activity from the Exploratorium, but the students love it every year. It can be expanded by asking students to improve the design, increase the volume or efficiency. I've also seen a headphone project follow this for which students have to make their own working headphones based on this speaker design. (NGSS Science & Engineering Practice right there!)
This year I'm adding a "Dissecting Headphones" lab to my unit. Thanks to RAFT I scored a gross of cheap ear bud headphones several years ago that I've been holding on to (hoarding again). Each pair of students will get a set of headphones so that they each get to dissect one ear bud. The instructions go step by step for these particular headphones and lead students all the way to the small magnet and coil. I've done it with high school aged students before and despite building the paper speaker only a few minutes before, they are shocked—shocked—that their ear buds work the same way. They use classroom scissors and a straight pin; they can use wire cutters too, but they are not required.
Suddenly they all start making connections. "This is how a microphone works, too!" and "That's why my headphones attract paperclips!" are heard all over the room. And it's magical.
The lab my students will do this week includes both the "Make A Speaker" and "Dissecting Headphones" labs in one file available as a pdf or google doc.
Uploaded on Oct 16, 2011 Video courtesy of the Association of Science-Technology Centers (ASTC), representing the science center and museum field worldwide. To learn more, visit www.astc.org. Follow us on Twitter: @ScienceCenters.
Captain Disillusion gets his Cosmos (NdT version) on, with nice references to his previous Tumba debunk, outlawed magnetic Buckyballs, and magnet boys.
Maybe it's just a symptom of their being too many people in the world: if someone can think it, someone will do it. How else to explain the digital magnet?
New York City writer Dann Berg decided to get a magnet implant about three years ago after reading about the trend online. The article described an implant gone wrong complete with graphic images of a magnet decomposing under flesh. Initially put off by the gory details, he decided to go for it anyway...
"I had a curiosity to explore the world in a completely different way," he explained.
As Jon Stewart would say at this point, "Go onnn...?"
Gradually his finger began to develop a "sixth sense" around any object that gave off electromagnetic waves.
"There is a half dome of vibration that surrounds the object almost like a tennis ball cut in half," he said. "The vibrations vary in strength depending on where I hold my finger and it's almost like the finger itself is vibrating against an invisible field of energy."
Well now the poor sod has my sympathy. A finger that jiggles when in proximity to objects that gives off electromagnetic waves? My my my. That's got to be rough since EVERYTHING GIVES OFF ELECTROMAGNETIC WAVES. Everything with a temperature greater than absolute zero, that is. So... everything. There may be some ideomotor effect going on here, but I doubt anything real is going on.
Physics teachers who stick to mechanics all year (by choice) must shoulder some blame for this story being floated as plausible. Magnets remain objects of mystery and imagination to those who have absolutely no understanding of how they work. Let's cut that population down wherever we get the chance, lest there be a resurgence in the sales of magnetic bracelets.
Implanting a magnet is certainly up there with getting a tattoo in terms of unnecessary body mutilation. Experts will likely disagree on which one requires the lesser threshold of good judgment.
UPDATE: Interesting comments, including some rebuttal from Dann Berg. Without an implant, I cannot argue what an implantee feels or when s/he feels it. He mentions a strong sensation near an operating microwave. There is reason to believe such magnetic fields are strong. And that they oscillate, so as to produce a vibrational sensation.
But here's the thing.
If you want to experience such vibrations, you don't need a rare earth magnet. All you need is a ferromagnetic object. A steel washer would work just fine. Upside? Your finger won't stick to an iPad (or earbuds, I imagine). Downside? You can't dangle a paperclip from your pinky.
Here's a simple demonstration showing the magnetism generated by a microwave transformer.
The wrench and razor knife are steel. They are not magnets.
We'll go through this gem and plenty more of a similar nature.
A seven year old boy in Serbia is shown to possess magnetic characteristics. Not to be outdone, Croatians show off a magnet boy of their own. And he's only six! Half a world away, an 11 year old Brazilian boy mystifies a doctor with a similarly attractive body.
But on an amusing Korean television program, James "The Amazing" Randi puts real-life Magnetos to the test. You know how this will end.
