Books and Articles by Cathleen Shamieh

Electronics is more than just schematics and circuits. By using various components, such as resistors and capacitors, electronics allows you to bend electric current to your will to create an infinite variety of gizmos and gadgets. In exploring electronics, use this handy reference for working with Ohm’s, Joule’s, and Kirchhoff’s Laws; making important calculations; determining the values of resistors and capacitors according to the codes that appear on their casings; and using a 555 timer and other integrated circuits (ICs).

You need a closed path, or closed circuit, to get electric current to flow. If there's a break anywhere in the path, you have an open circuit, and the current stops flowing — and the metal atoms in the wire quickly settle down to a peaceful, electrically neutral existence. A closed circuit allows current to flow, but an open circuit leaves electrons stranded.

The figure shows the front and back of one type of mini-speaker. Speakers usually come with leads attached. The leads are twisted together to keep things neat and tidy. You attach the leads to components in your circuit so that electrical current passes from your circuit into the speaker. The speaker then converts the current into sound.

A schematic (pronounced "skee-mat-ick") is a diagram of a circuit. Schematics use symbols to represent circuit components and lines to show the connections between components. What schematics don't do is tell you how to arrange your circuit (or whether or not to use foam cutouts). It's up to you to decide how to lay out your circuit.

Look at the two 2N3906 PNP transistors shown here. Do they look like the 2N3904 NPN transistor? Yup. Does it matter if you get the 2N3904 and 2N3906 transistors mixed up? Yessirree, Bob! Two PNP transistorsIn this project, you use both a 2N3904 NPN transistor and a 2N3906 PNP transistor, so you really need to keep track of which is which.

In scientific terms, radio is the transmission of a certain kind of electromagnetic energy through the air. Electromagnetic energy is energy that is radiated (meaning emitted) by an object and travels in waves, similar to the way sound is transmitted. X-rays, microwaves, visible light, and ultraviolet light (think sunburn) are other types of electromagnetic energy.

Unfortunately, there isn't a store in a shopping mall close to your house where you can just walk in, pick out all the electronics parts you need, plunk down about $100, and go home and start building projects. Even RadioShack stores no longer carry a wide variety of electronic components. So, you will need to order many of your supplies online, which means you have to plan to allow time for shipping.

The battery's job is to provide the electrical energy needed to power the LED in your flashlight circuit. Chances are you're familiar with 9-volt batteries like the one shown. Components needed to build an LED flashlight. Explore your battery Every battery has two terminals, which are the metal pieces that stick out from the top of a 9-volt battery (see the following figure) or the metal ends of an AA, AAA, C, or D battery.