Archive

Posts Tagged ‘electromagnetism’

Happy Birthday Nikola Tesla: ‘Poker Face’ Played On Tesla Coils!

July 11, 2011 1 comment

Yesterday was Nikola Tesla’s birthday, the man who is most famously known for giving us alternating current (AC).

In celebration, enjoy ‘Poker Face’ by Lady Gaga played with Tesla Coils!

 

Teaching Electricity and Magnetism: Part II

March 30, 2011 2 comments

ResearchBlogging.org
This is the second part of my posts about teaching Electricity and Magnetism (EM). Part I can be found here, which dealt with the confusion of students in learning electricity and magnetism together. Part II deals with a paper looking at ways to help improve teaching methods for EM. The paper is entitled “Using multimedia learning modules in a hybrid-online course in electricity and magnetism“.

When I was still TAing (about 2 years ago) the University was starting to implement a new way of performing tutorial sessions. They were going to do it online. This was done by the students logging into a virtual classroom with the other students and were able to type out questions to the TA. The TA was in a computer lab somewhere and outfitted with an electronic on-screen writing tool (don’t ask me what it’s really called) and would work out problems on their screen by hand, which the students were able to see in the virtual classroom.

When asked if I wanted to participate in this type of tutorial, I refused. Call me a dinosaur (I’m only 26, but whatever) but I wanted to be in the room with the students when I taught them.

But do online and multimedia learning tools help? Or are they worse? That was the topic of this study.

A multimedia learning module (MLM) was developed by the Physics Education Research Group at the University of Illinois at Urbana Champaign and implemented as a pre-lecture assignment to students in an introductory physics course. MLMs are interactive online exercises which include flash animations which introduced physics concepts to the students. The MLMs were about 12-15 minutes long.

So the goal of the study was to determine if using MLMs prior to learning the concepts in class resulted in better grades for the students and a better student experience. The study tried them out in an introductory Electricity and Magnetism course in the Fall of 2008 at California State Polytechnic University at Pomona.

They used two different sections of the course as the control group and the experimental group. The control group (N = 48) had only the traditional coursework. The experimental group (N = 34) used traditional coursework in conjunction with the MLMs. To make sure any increase in performance was not simply due to increased time spent on the material in the experimental group (i.e. classtime + time spent on MLMs) the amount of time spent in the class was reduced by one-third for the experimental group.

Students in the experimental group viewed the MLMs prior to learning the material in class. Both groups were approximately equal in academic performance  prior to taking the course, as determined by a survey.

Student performance after the term was measured by a multiple choice test, as well as the results of answering questions in class using a personal response system called a  “clicker“. Students were also asked to fill out a questionnaire to rate the usefulness of different aspects of the course, such as the textbook or the MLM.

Students who used the MLM showed an 8% higher normalized gain than those in the control group (45% compared to 37%) in their multiple choice test. In addition, students who used the MLMs answered a slightly higher percentage of in-class clicker questions correctly (60 +/- 4.0%) compared to the control group (54 +/- 3.0%). This leads to an effect size of 0.25, which is considered a small effect.

Finally, students rated the usefulness of the different course material on a scale of 1 (not useful at all) to 5 (extremely useful). Students in the experimental group rated the MLMs higher (~2.5) than the course textbook (~1.3).

So does multimedia course material improve student performance? Well these results show that it is no worse than traditional coursework. One thing to note is that any increased improvement of the group which did MLMs compared to the control group is very small. With a sample size of about 40 students in each group, it is difficult to draw any firm conclusions.

In addition,

It is worth mentioning that the comparison of final exam scores between students in the control and those in hybrid-MLM group showed no significant differences.

So at the end of the day, students did roughly just as well in both groups.

But this is an interesting study nonetheless. Probably the best thing to do would be to offer the MLMs as an optional and additional resource to the students, without cutting out the in-class learning time. Everybody learns differently, whether it be through visual stimuli, auditory or simply repetitiveness. The important thing is to make resources available so people of all learning styles can benefit.

I felt I could teach my students best face-to-face, so I declined to use the new fangled technology for online tutorials. But I understand they are still being used, and some students actually prefer them. So I guess in the end, this study showed that no single manner of learning is better than any other. Do what works for you and stick with it.

Sadaghiani, H. (2011). Using multimedia learning modules in a hybrid-online course in electricity and magnetism Physical Review Special Topics – Physics Education Research, 7 (1) DOI: 10.1103/PhysRevSTPER.7.010102

Teaching Electricity and Magnetism: Part I

March 29, 2011 2 comments

ResearchBlogging.org

When I was a physics TA, there were two topics which always got the students easily mixed up. The first was Newton’s Laws; students had a hard time knowing which law to apply in what situation. But with a little practice and teaching, they soon found that you could follow a very specific procedure to solving any problem involving Newton’s Laws, which helped immensely.

Electricity and Magnetism (EM) was different, however. There really is no set procedure for solving an EM problem. There are strategies and guidelines, but no step-by-step ways of solving EM problems like there is for Newton’s Laws.

I’m not the only one who has noticed this either. Two papers were published this month in Physical Review Special Topics – Physics Education Research. The first was entitled “Interference between electric and magnetic concepts in introductory physics“.

This study looked at the difficulty students had in determining which direction the force on a charged particle would be, if it were in either an electric or a magnetic field.

For a positive charge in an electric field, the force is always in the same direction as the field. If the charge is negative, the force is in the opposite direction of the electric field. Students generally don’t have a problem with this rule; that is, until you introduce the concept of a magnetic field to them.

In a magnetic field, the force on a charged particle is always perpendicular to the magnetic field lines. So when you get to the end of the term and you ask an EM question, students often (understandably) get confused which rule they should use.

The main hypothesis of the study, therefore, was that students have trouble because they learn about electric fields first, and then apply those lessons to working with magnetic fields.

You can test this hypothesis by seeing if the opposite is true. Does learning about the magnetic field first negatively affect the way students answered questions about electric fields?

The subjects (I mean, ‘participants’ hehe) of the study were students in an introductory physics course at The Ohio State University. The students were asked to answer EM related physics questions. They were split up between groups which had learned i) nothing about EM, ii) electricity but not magnetism, iii) magnetism but not electricity, and iv) having learned both. The order in which the questions were asked and some other variables were randomized for better results. Below is an example of the type of question the students were asked.

Can you get the answer to this question? For the left hand side the answer is 'e - Into Page' and for the right hand side the answer is 'f - Out of Page'

There are actually several results from this study, so if you are interested in them all I encourage you to read it (it is free to read). But the main hypothesis turned out to be true:

directly after instruction about magnetism, many students answer that the direction of the force on a charged particle moving through an electric field is perpendicular to the electric field, presumably by employing the same right-hand rule that was learned for magnetic forces. Thus, despite the fact that directly before magnetic force instruction students were answering electric force questions correctly, up to two weeks (and possible longer) after they learn about magnetic force, they answer electric force questions as though they were magnetic force questions.

So the authors actually showed that it is not electric fields or magnetic fields alone that confuse students, but after learning both they get them mixed up, which makes sense. It doesn’t seem to matter, either, which they learn first. After learning both electric and magnetic fields they still get confused.

The authors suggest (and I agree) that to combat this the instructor must frequently point out the distinction between electric and magnetic forces. It is a difficult thing to get a feel for, kind of like learning the offside rule in hockey.

A good strategy is always visual demonstrations. Take for example this video of MIT professor Walter Lewin demonstrating the perpendicular magnetic force (jump to around 46:40 for the demonstration):

So what else could we do about students having trouble with EM? What about online and multimedia tools?

That will be the topic of Part II of this series.

Scaife, T., & Heckler, A. (2011). Interference between electric and magnetic concepts in introductory physics Physical Review Special Topics – Physics Education Research, 7 (1) DOI: 10.1103/PhysRevSTPER.7.010104

Wi-Fi the New Danger to Children…Apparently

August 16, 2010 2 comments

Well, as if we didn’t have enough to be afraid of in the pseudoscientific world, now we have to be afraid of our wireless internet connection.

Parents in Barrie and other northern Ontario towns have called the public school board to remove its recently installed Wi-Fi system because, they claim, it is making their children sick.

The symptoms include memory loss, trouble concentrating, skin rashes, hyperactivity, night sweats and insomnia.

These are extremely non-specific symptoms, and most of them can describe pretty much every young child I know at some point in their lives.

Said one of the parents:

“I’m not saying it’s because of the Wi-Fi because we don’t know yet, but I’ve pretty much eliminated every other possible source.”

Really? You’ve eliminated EVERY possible source? Thats quite a bold statement when it comes to environmental factors.

Now, its hard to blame these parents for looking out for their kids, but this is a clear cut case of poor understanding of technology and media hysteria.

Oh yes, I’m talking about YOU CBC!

For example, take the “expert” they got to comment on this story, one Professor Magda Havas from Trent University (in my hometown of Peterborough, Ontario, incidentally).

So what does this professor say? From the CBC article:

Claims by Health Canada that Wi-Fi is safe provided exposures to radiation are below federal guidelines are “outdated and incorrect,” based on the growing number of scientific publications reporting adverse health and biological effects, Havas wrote.

Havas did her Ph.D in Botany, so what makes her an expert electromagnetism, I have no idea. But from her website (note the advertisement to her book at the bottom), it seems she is involved in fear mongering for just about every junk science theory about electromagnetism affecting humans, including the dangers of power lines and cell phones (all these technologies have repeatedly been shown to be safe).

It amazes me that they couldn’t find an actual expert in electromagnetism to comment on this story. But then, it wouldn’t increase readership would it?

But shall we interrupt this exercise in bad science and bad science reporting for some REAL science?

The energy deposition from a typical wireless signal is roughly 100 times less than exposure to a cell phone (which remember, has been shown to be a perfectly safe level). It is also thousands of times less than current government regulated safety levels, AND is less than normal background radio frequency radiation. Maybe that rat-bastard Ryan Seacrest and his Top 40 crap is making us all sick!

Now how about a bit of logic? The parents claim that these symptoms go away on the weekends. This makes no sense as children are exposed to wireless signals at their home, at the mall, the airport, restaurants, pretty much everywhere. If it was the Wi-Fi and these children are truly sensitive to it, they should be sick virtually all the time.

And what about children living in an apartment building, where there are literally dozens of wireless signals in their vicinity. Shouldn’t they be affected at home as well? Shouldn’t this be more widespread?

Ok, so when I start freaking out about stuff like this, my lovely girlfriend invariably asks “So what COULD it be, if not the Wi-Fi?”

My Lovely Girlfriend. Yes, I have one!

Well, remember these symptoms: trouble concentrating, hyperactivity, insomnia, night sweats. This sounds like me when I was a kid. I was always having trouble sleeping and running around like a madman. These tended to go away on the weekend though, when I could just relax and play video games. Also, kids don’t like school; they could get stressed out and cause these symptoms, which would of course go away on the weekends and in the summer. They may be staying up too late on weeknights, so sleep deprivation could easily cause some of these symptoms.

Want to know what I really think is happening? I think a child got sick with something, and an over-zealous parent read something about Wi-Fi being dangerous on the internet. They heard that the school had recently installed Wi-Fi and BAM! you got yourself the perfect storm of fear.

If you take nothing else from my blog, please take this: Correlation does NOT equal causation.

Just because these children got sick after (several months after, which is kinda weird. Shouldn’t they have gotten sick right away?) the school board installed wireless networks, does NOT mean wireless networks made these children sick.

I could just as easily say the sun rose after my alarm clock went off this morning, therefore my alarm clock caused the sun to rise. It is a logical fallacy and stories like this are riddled with them.

So don’t worry folks, your internet is just fine. Continue using your laptop (to read this blog, hopefully) and your cell phone without fear. With every new technology there will be those who try to convince you its bad. And unfortunately, there will also be protective parents to make a fuss over it.

The (Simple) Physics of the ‘God Particle’

July 21, 2010 1 comment

The ‘God Particle’.

Pretty catchy name. Its been in the news quite a bit lately. But what is it exactly? And why would they call it the ‘God Particle’? Especially since science and religion get along about as well as Frank and Estelle Costanza!

Well in this blog post, I’m going to give you a basic and (hopefully!) entertaining explanation of what the God Particle is, and why we should care. So let’s start at the beginning.

The ‘God Particle’ is also (and more accurately) known as the Higgs Boson. Described in a single sentence, it is believed to be the particle that gives mass to all other particles in the Universe.

Ok, that SOUNDS important, but its still a bit hard to understand, so here’s a bit more thorough explanation.

Everything in the universe is made up of particles. And there are several different kinds of particles.

All the matter in the universe is made up of atoms. Atoms are made of a nucleus, which is found at the center of the atom and has neutrons and protons in it. Surrounding the nucleus are electrons, which are much smaller and fly around the nucleus in a circle, or an ‘orbit’.

Groups of atoms can get together and form molecules, and big groups can get together to form rocks, trees, and Maria Sharapova.

So thats 3 particles we have already described (protons, neutrons, and electrons). These 3 particles have mass; this essentially means that they weigh something.

But there are other types of particles out there too. For example, there is the photon.

Photons are are basically light. They are tiny packages of energy that make up a beam of light. They also make up radio waves, x-rays, and gamma rays (the stuff that gave the Fantastic Four their powers).

But photons are different from, say, protons, because they don’t have any mass. They carry light energy from the sun, for example, to the Earth. Or they can carry radio messages from the radio station to your house. So photons are like messengers; as such, they are sometimes called “messenger particles”.

A “messenger particle” is also called a boson. Bosons are really cool because they actually DO something. What do I mean by that?

Well, if you remember high school physics or chemistry class, you know there are 4 forces in nature. Gravity is one of them, and it is the most familiar too us. Its what keeps us firmly planted to the ground. Electromagnetism is what makes electricity, light beams, radio waves, and magnets work.

You Can Visualize a Magnetic Field with Iron filings and a Bar Magnet

The other two forces are a little less familar. They are called the Strong nuclear force, and the Weak nuclear force. These two are basically what holds the nucleus of the atom together, and make it behave the way it does.

So what does this have to do with anything? Well remember bosons are messenger particles. The photon carries the electromagnetic force “message”. The other forces in nature have bosons as well that carry their “messages”. Gravity has the “graviton” (which hasn’t been observed yet but we think its out there). The strong nuclear force has the “Gluon” (because it ‘glues’ the nucleus together). And the weak nuclear force has the “W” boson (it doesn”t get a cool name because its not cool).

Ok, now we get to the Higgs boson. So, since it is a boson, it must be the “messenger” of something right? So what is it the messenger of?

Well, remember I said that protons, neutrons and electrons have mass? But the photon does not have any mass. Why is that? What is it that makes one particle have mass, and the other not have mass? Even a couple of the bosons have mass! Thats just freakin’ weird.

So particle physicists (one of the named Peter Higgs, oddly enough) came up with a theory. They think there is some kind of a field in the universe called the “Higgs Field”. Its kind of like a gravity field, or a magnetic field. Just like a magnetic field will interact with some iron to pull it in one direction, the Higgs Field will also interact with particles. But instead of pulling at them, the Higgs Field gives these particles mass! It makes them heavy!

The theory also says there should be something called the Higgs boson: an actual particle that carries the Higgs field “message”. And thats what we are trying to find. The Higgs boson is the messenger particle of the Higgs Field, which is (theoretically) what gives particles their mass. If we do find it, then we know our theories about how the universe is made are on the right track. It would be HUGE breakthrough for physics!

One problem: the Higgs boson is supposed to be heavy! Well, for a particle its pretty heavy.

In fact, the only way to actually “make” one is by slamming together stuff like protons at close to the speed of light in what we call a “particle collider”. And we need to slam them together at a really BIG energy, so we need a BIG collider. Thats why we have the Large Hadron Collider.

The Large Hadron Collider in Geneva, Switzerland

Ok, so thats the explanation of what the Higgs boson is and why we should care. So why is it called the ‘God Particle’.

Well, a guy named Leon Lederman wrote a book called “The God Particle: If the Universe Is the Answer, What Is the Question?which was actually about the Higgs boson. Calling it the “God Particle” was a kind of grandiose name because it suggested we knew what it was that gave particles mass, what made they heavy or “real”. Very “god-like” I suppose”.

The term “God Particle” also showed up in Dan Brown’s novel “Angels and Demons”. In the book some claimed that the discovery of the particle would prove the existence of God.

Finding the Higgs would be great, but would hardly prove the existence of God. The use of these terms is largely to increase media interest.

Phew, well there you have it. If you want to hear more about Physics news as it happens you can follow me on Twitter! Or you can follow the Large Hadron Collider on Twitter!