(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 Home 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 stores. 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.