Experiencing Electricity13Experiment 3: Your First CircuitCleanupandRecyclingThe first AA battery that you shorted out is probably damaged beyond repair. You should dispose of it. Putting batteries in the trash is not a great idea, be-cause they contain heavy metals that should be kept out of the ecosystem. Your state or town may include batteries in a local recycling scheme. (Califor-nia requires that almost all batteries be recycled.) You’ll have to check your local regulations for details.The blown fuse is of no further use, and can be thrown away.The second battery, which was protected by the fuse, should still be OK. The battery holder also can be reused later.Experiment 3: Your First CircuitNow it’s time to make electricity do something that’s at least slightly useful. For this purpose, you’ll use components known as resistors, and a light-emitting di-ode, or LED. You will need:• 1.5-volt AA batteries. Quantity: 4.• Four-battery holder. Quantity: 1.• Resistors: 470Ω, 1K, and either 2K or 2.2K (the 2.2K value happens to be more common than 2K, but either will do in this experiment). Quantity: 1 of each resistor. • An LED, any type. Quantity: 1. • Alligator clips. Quantity: 3.SetupIt’s time to get acquainted with the most fundamental component we’ll be us-ing in electronic circuits: the humble resistor. As its name implies, it resists the flow of electricity. As you might expect, the value is measured in ohms. If you bought a bargain-basement assortment package of resistors, you may find nothing that tells you their values. That’s OK; we can find out easily enough. In fact, even if they are clearly labeled, I want you to check their values yourself. You can do it in two ways:• Use your multimeter. This is excellent practice in learning to interpret the numbers that it displays.• Learn the color codes that are printed on most resistors. See the following section, “Fundamentals: Decoding resistors,” for instructions.After you check them, it’s a good idea to sort them into labeled compartments in a little plastic parts box. Personally, I like the boxes sold at the Michaels chain of crafts stores, but you can find them from many sources.BAckgroundFatherofelectromagnetismBorn in 1775 in France, André-Marie Ampère (Figure 1-40) was a mathematical prodigy who became a science teacher, despite being largely self-educated in his father’s library. His best-known work was to derive a theory of electromagnetism in 1820, describing the way that an electric current generates a magnetic field. He also built the first instrument to measure the flow of electricity (now known as a galvanometer), and discovered the element fluorine. Figure 1-40. Andre-Marie Ampere found that an electric current run-ning through a wire creates a mag-netic field around it. He used this principle to make the first reliable measurements of what came to be known as amperage.