Experiment 26: Tabletop Power Generation

Chapter Experiment 26: Tabletop Power Generation

Make Electronics Book Learning by Discovery
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Make Electronics Book Learning by Discovery

  • What Next?239Experiment 26: Tabletop Power GenerationExperiment 26: Tabletop Power GenerationIf you have just three components, you can see magnetism generating elec-tricity right in front of you, right now. You will need:• Cylindrical neodymium magnet, 3/4-inch diameter, axially magnetized. Quantity: 1. (Obtainable online at sites such asactionURI(http://www.kjmagnetics.com): http://www.kjmagnetics.com.)• Spool of hookup wire, 26-gauge, 100 feet. Quantity: 1.• Spool of magnet wire, quarter-pound, 26-gauge, about 350 feet. Quan-tity: 1. (Search online for sources for “magnet wire.”)• Generic LED. Quantity: 1.• 100 μF electrolytic capacitor. Quantity: 1.• Signal diode, 2N4001 or similar. Quantity: 1.• Jumper wires with alligator clips on the ends. Quantity: 2.ProcedureYou may be able to make this experiment work with the spool of hookup wire, depending on the size of the spool relative to the size of your magnet, but as the results are more likely to be better with the magnet wire, I’ll assume that you’re using that—initially, at least. The advantage of the magnet wire is that its very thin insulation allows the coils to be closely packed, increasing their inductance.First peek into the hollow center of the spool to see if the inner end of the wire has been left accessible, as is visible in Figures 5-18 and 5-19. If it hasn’t, you have to unwind the wire onto any large-diameter cylindrical object, then rewind it back onto the spool, this time taking care to leave the inner end stick-ing out.Scrape the transparent insulation off each end of the magnet wire with a utility knife or sandpaper, until bare copper is revealed. To check, attach your meter, set to measure ohms, to the free ends of the wire. If you make a good contact, you should measure a resistance of 30 ohms or less. Place the spool on a nonmagnetic, nonconductive surface such as a wooden, plastic, or glass-topped table. Attach the LED between the ends of the wire using jumper wires. The polarity is not important. Now take a cylindrical neo-dymium magnet of the type shown in Figure 5-20 and push it quickly down into the hollow core, then pull it quickly back out. See Figure 5-21. You should see the LED blink, either on the down stroke or the up stroke.The same thing may or may not happen if you use 100 feet of 26-gauge hook-up wire. Ideally, your cylindrical magnet should fit fairly closely in the hollow center of the spool. If there’s a big air gap, this will greatly reduce the effect of the magnet. Note that if you use a weaker, old-fashioned iron magnet instead of a neodymium magnet, you may get no result at all.Figure 5-18. An everyday 100-foot spool of hookup wire is capable of demonstrating the inductive power of a coil. Figure 5-19. Magnet wire has thinner insulation than hookup wire, allowing the turns to be more densely packed, inducing a more powerful magnetic field.