Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Archive for April 2009

If you don’t know what a lateral thinking puzzle is, google it.  These are great puzzles to make the kids think a little differently.  The kids make so many assumptions, I’m always struggling to find ways to open up their thinking process.

I had a period to kill with one of my classes, so I pulled out a few of these puzzles.  It’s real important to lay down the rules for the puzzles.  They need to take turns asking questions, they get into it, but I can’t answer questions when they talk over each other.  The questions have to be in a form that I can answer with yes or no.  Sometimes I answer with “doesn’t matter” or “I don’t know” and that irritates them because it wasn’t in the rules.  It was, I just didn’t tell them.

The idea is for them to start asking questions and realizing they assumed an incorrect body of information.  Here’s an example, it’s so common, I don’t think I’m ruining any great puzzle sharing it.

A body is discovered in a park in Chicago in the middle of summer.  It has a fractured skull and many other broken bones, but the cause of death was hypothermia.

The solution is usually in the form of a story that the kids need to work out through their questioning.  Here is the solution to the above puzzle:

A poor peasant from somewhere in Europe desperately wants to come to the United States.  Lacking money for airfare, he stows away in the landing gear compartment of a jet.  He dies of hypothermia in mid flight and falls out when the compartment opens as the plane makes it final approach.

Check out some online sources and books at the stores.  I have a couple of books, but I find most of the puzzles aren’t good enough to use in class.  I might highlight for or five puzzles from a small book of puzzles.  Tell me how they work out for you.


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This mini-lab worked out really well.  In fact, quite of few kids surprised me by getting into building circuits.  I know a lab goes well when nobody bails or gives up in frustration.

I introduced series and parallel circuits with three quick overheads.  I also taught them the schematic symbols for a battery, switch, and bulb.  I helped them out by drawing the schematic for the first problem.  The attached document is pretty much self-explanatory, but I would suggest you have the kids read the last couple questions before they start building.

I had the kids in groups of two.  Each group needed a 3v battery pack (2-D cells), two light bulbs in holders, two knife switches, and about 6 sets of alligator jumpers.  You could use pre-cut wires, I had the jumpers available.

series-and-parallel-switches

With the introduction to series and parallel circuits, the lab took the entire class period to complete.

It’s not about being politically correct.  Limes are cheaper than lemons.  A bag of 5 limes was $1, lemons were $2.  Since we were sticking metal in them and then throwing them away, frugality wins.  Besides, I have some leftovers that may become margaritas.

Now, I ran out of time and didn’t create a lab sheet, so I had to wing this a bit.  We did have a kit from Carolina that included electrodes of Fe, Cu, Al, and Zn.  I decided I would have less trouble if I did the cutting into the limes.  I used a plastic knife and cut two slits about 3/4″ apart, large enough for the electrodes to easily slip into the lime.

On the board I created a simple 4×4 matrix of the metals and had the students test each metal pair as electrodes.  I also had them test Fe-Fe, and Cu-Cu, etc.  That meant they had to share electrodes to get the similar pairs.  They found that only dissimilar metals created a voltage and the voltages were not all equal.  Cu-Zn created the largest, at around .9 volts.

Next, I had them pull out change from their pockets and try the coins as electrodes.  I also had some galvanized screws (zinc coating) for them to use.

Once they had a feel for what makes their battery work, I gave them each an LED for them to try to light up.  A single battery didn’t have enough voltage, so they had to partner up with another group and figure out (with some guidance in the form of a drawing on the board) how to wire the batteries in series.  With two, they could get a red LED to light up.  We had to turn out the lights to make it visible.  The green LEDs seem to require more power and didn’t light up with the same batteries.  They also wired three together and made the light even brighter.

Yes, I needed more organization.  Tomorrow we do series and parallel circuits using switches and light bulbs.  It’s fourth quarter and I feel like I’m out of energy myself.

I now feel qualified to put something up on this post.  We played for two whole days in my physical science class, and the kids still want more.  Another day in my three physics classes, and I’m battle ready.

I began by showing the balloon on the bald teacher’s head and sticking it to the wall.  Trust me, nothing gets them going more than a mostly bald teacher trying to rub a balloon on his hair. Amazingly, there were quite a few students that had never seen a balloon charged up and stuck to a wall.

We then went to the standard acrylic/fur type of static charge, explaining how the charges separate.  I caused paper and bits of styrofoam to jump from the charge.

The van de graaff generator is exactly like those static creating devices, but it just keeps making more and more static.  Here are a few ideas I have either done or picked up on the internet.  One important note; I got all of the kids up and involved.  Some of them were scared, but after the girls charged up their hair without pain, the chickens were shamed into bravery.

Before doing each of these demonstrations, I ask the students what they think will happen:

1.  I take a bunch of holes from a paper punch and put them on top of the dome.  Then I turn the machine on and the holes fly up into the air.  The dome and paper, all having the same charge, repel each other.  The paper holes spray up in a fountain of white dots.

2.  I tape strips of paper to the dome.  The paper stands up and stays standing until the dome is discharged.  This is a good precursor to the hair thing.  They don’t expect the paper to stay up in the air when the machine is off.

3.   I use the grounding electrode to make the sparks jump really far.  Let the generator run until you hear the ozone crackling.  Then you get a great big spark.  I use this to build some tension and fear of the generator because I’m asking for volunteers to do the hair thing.

4.  Making hair stand up.  The student needs to stand on a plastic milk crate or something to insulate them from the floor.  One student wanted to try this standing on the ground.  I think he had sweaty feet, he said (and we heard) the discharge going through his feet into the floor.  I wish I could tell you how to know what kind of hair works best.  Really long hair is too heavy, really short hair is too stiff.  Hair color doesn’t seem to matter, although dark is easier to see than blond.  For some reason, the hair of the black girls worked best.  I’d love to post the pictures, but posting pictures of student’s is a no-no, at least without written permission.

5. Fluorescent light bulb lights up.  It does not need to come into contact with the dome, the spark jumping to the glass with light up the bulb.  We found that placing the bulb about 1 inch from the dome gave the best results.  Stand on a piece of wood or you will feel the shocks in your toes.

6.  We made a chain starting with one person charged up.  He touched the next person, but held on.  Now they both charged up and continued to another person.  If the person getting shocked was sitting in one of our desk/chair units, he or she got a constant stream of shocks to the legs and back side.

7.  Water bottle on top produces lightening like show.  I’m going to tell you to be careful with this one.  It works pretty well at first, but the massive sparking in the bottle actually burned through the bottom of the plastic bottle.  Once they started leaking, they wouldn’t charge up.  I had to use a different bottle for each class.  More importantly, the bottle kept the charge.  Just holding the bottle and moving it around gave a constant stream of rather painful shocks.  At one point I was holding the grounding rod and the bottle.  I touched where the bottle was leaking through the bottom and I got an extremely nasty jolt across one arm to the other.  Be careful with this one.

8.  A balloon placed near the dome is first attracted, then when it touches the dome, the charge is conducted and it is repelled.  The charge leaks off and this repeats over and over again.  I used this to lead into Coulomb’s Law and the force due to the electric charge.  Again, you will want to stand on something to insulate you or you will have toe sparks.

Here are a few demonstrations that I haven’t yet tried:

  • Mini pie tins stacked on top fly away one at a time – the pie tins I tried were too big.
  • Soap bubbles are repelled as they get near the dome.

Any more?


What’s New in 2013/2014?

Every year brings a change, this one is no exception.

I will be picking up the sophomore honors Algebra II class to keep them separate from the juniors. This should help accelerate them and put them on a stronger track towards Calculus. Looks like there will be only one section each of Physics and Calculus, but still two of Robotics & Engineering.

Hot topics this year are going to be the Common-Core Standards, Standards-Based Grading (SBG), improving AP Calculus scores, and somehow adding Python, maybe as a club.

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