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Teaching in LA

03 Dec

Video: Brainiacs – Electric Fence

Posted in Uncategorized on 03.12.11 by Frank

Link to video: Brainiacs – Electric Fence

How I use it

Before each “experiment”, pause the video and ask your students to predict what will happen. Have them discuss their predictions with their partner/group and write their prediction on their whiteboard (or call on them randomly, or have them write it on a sheet of paper). Continue playing the video clip. After the “experiment”, ask your students what actually happened (since sometimes they don’t pay attention, don’t catch important details, or just see the results differently than you may).

Worksheets

If you prefer the ready-out-of-the-box approach…

Worksheet by Dean Baird (veteran physics teacher at Rio Americano High School and host of Sacramento PTSOS)

Worksheet by Elisa Fanchiang (physics teacher at Animo Locke Tech Charter High School)

To download and save video to your computer

This works for any YouTube video (and sometimes other video services too)…

  • Go to keepvid.com: Click here to go to keepvid.com
  • Copy and paste the video link URL into the box and click the “Download” button
  • Save the video that’s your preferred format and resolution (or click the one labeled “Max 480p” if you’re not sure)
  • If your video program cannot view the file, try downloading and installing VLC media player

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03 Dec

Resources for NPTW (New Physics Teacher Workshop) Winter ’11

Posted in Uncategorized on 03.12.11 by Frank

Featured at Today’s Workshop

Links/Resources

Frank’s Demos

Not Featured at Today’s Workshop but Relevant or Worth Mentioning

Links/Resources

  • I do a few basic battery/wire/bulb labs, but you may have a hard time doing those if you don’t have batteries/wires/bulbs. If you’re the type to buy your own class materials (or you just need them urgently), you can buy batteries and wire pretty easily and at reasonable prices, but those little bulbs are generally pricey at hardware stores ($2-4 each). Try getting some cheap bulbs at your local dollar stores (a great place for teacher supplies in general). I found packs of 4/$1 at my favorite local dollar store. Also, if your students are normal for their age, they’ll want to add batteries in the circuit until the bulbs burn out. I recommend getting a string of old Christmas lights and removing the individual bulbs from their sockets for this purpose.
  • Global Physics Department (online physics teachers community) – Live online meetings every Wednesday.
  • Physics blogs – There are several physics teachers who also blog, giving us excellent resources and inspiring great conversations. I won’t try to post every blog, and there is no “best” blog, but I’ll point you to the blog of the guy who many would agree is the hub of the online physics community (Frank Noschese’s Action-Reaction). A great source for inspiration and discussion on physics content and pedagogy (and more!).

Labs/Activities

  • Squishy Circuits
    Targeted toward children, but you may find certain aspects useful. This was not featured at today’s workshop, but James’ Play-Doh resister reminded me of this. Addresses basic circuit concepts (open/closed circuits, Ohm’s Law, series/parallel circuits).
  • Scotch Tape electrostatics – There’s a simple electrostatics lab you can do using just a few pieces of Scotch tape. There’s a few variations of this, but I just found a random one on the internet.

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    03 Dec

    Magnet Through a Copper Tube

    Posted in Uncategorized on 03.12.11 by Frank

    Drop a magnet down this non-magnetic copper tube and witness the magic (physics) that is Lenz’s Law (or Eddy Currents… or… something).

    Ingredients:

    • A ~ 5 ft. copper pipe (I used 1/2″ diameter, might have to ask to get it cut to length at hardware store)
    • Strong “disc” or “ring” neodymium magnets with diameter less than pipe, (available for reasonable prices by searching for “neodymium magnets” on eBay)

    Directions:

    1. Establish that the copper is not magnetic. Have a student use the magnets to pick up something magnetic (paper clips, nose ring, etc.), then attempt to attract the copper pipe. It shouldn’t work. :o|
    2. Establish that gravity functions properly through the copper pipe. Have the student hold the pipe vertically, then drop an object (pen) through the pipe. Did the pen seem to accelerate down through the pipe at approximately 9.8 m/s/s? If yes, then physics is working.
    3. Do the same demonstration, but with a short stack of magnets long enough that they don’t flip in the pipe. After you drop the magnets at the top of the pipe, take a leisurely stroll to your desk and back, then reach out to catch the magnet.

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      03 Dec

      Electric Shocker Plans and Notes

      Posted in Uncategorized on 03.12.11 by Frank

      (Updated 1/18/2016)

      Deliver a (relatively) safe electric shock with this amusing device. Not recommended for individuals with heart problems.

      Here are the plans I used:

      Electric Shocker Plans by menkster


      (Document created by Lawrence Sverdrup)

      Materials notes:

      • For the 9V doorbell, I found one for around $10 (shipping included) on Amazon
      • The transformer costs around $10 at┬áHome Depot (make sure it steps up/down 10x, so a 120V/12V transformer)
      • Instead of the switch featured in the plans, I chose a momentary push button switch available at Home Depot┬ástores. I prefer the default state of the circuit be open, and closed only when intended to be, for only the duration intended.
      • For the handholds, I used cheap metal conduit, although any metal pipe should work. I used alligator wires to connect the handholds to the device.

      Usage ideas

      • You may want to remind students of a few concepts. They may be hesitant to fully grab the terminals. Actually, the more surface area contacting the terminal feels less intense than a small surface area of contact since a larger contact area means a larger cross-sectional area for the current to travel through. That’s why the feeling is most intense in the forearms and felt a lot less in the torso. Touching the terminal with a single finger is not a good idea.
      • Enforce the ideas of open circuits, closed circuits, and short circuits. If the student holds just one terminal, will he feel a shock? What if he held it with both hands? If the student holds both terminals, will he feel a shock? What if he holds both terminals together so that they’re touching? Will he feel a shock then? He may be shocked… intellectually! :oO
      • Demonstrate the inverse relationship between resistance and current in a series circuit (more resistance = less current) by having students hold hands to form a chain, then the students on the end of the chain each grab a terminal with their free hand (to form a complete loop). The more students in the chain, the less buzz they all feel. This also creates a snowball effect in getting more students to participate in the circle (since sometimes students can be quite hesitant). Also, hesitant students will want to stay away from the terminals and instead be in the “middle” of the chain. Prompt them to think whether there’s a difference in current in those positions.
      • In a one-student/shocker circuit, insert in series a large bowl of water (so one terminal is dipped in the water and the student’s hand that otherwise would be holding that terminal is instead dipped in the same water). Deliver shock. Salt the water to increase its conductivity. Deliver shock again. Have student feel the difference in conductivity. Try different liquids (Gatorade, etc., stuff with electrolytes, or distilled water, which shouldn’t conduct much. Blood would just be plain creepy.)
      • Set up the device to deliver a normal shock full strength to one student. Tell them to try to let go of the handholds when they feel the shock. Hold down the button and watch them try to let go. Explain that their muscles are controlled by electrical signals from their brain and that the signals of the shocker are stronger than those brain signals, so that’s why they’re unable to let go of the terminals, even though their brain is telling them to let go. Do a quick check for understanding by asking the student to summarize that in their own words. Evaluate the student’s response and provide feedback. Then, let go of the button.

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