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.

You may be familiar with LEDs if you have an LED flashlight or use LED bulbs in your home. An LED, or light-emitting diode, is a device made of a special material known as a semiconductor. A diode is the simplest type of semiconductor device (meaning, component). Diodes, LEDs, and other semiconductor devices have unique properties that make them useful.

To limit the current that flows from a 9-volt battery through your LED, you insert a resistor in your circuit. Resistors slow down current, like a kink in a hose slows the flow of water.The figure shows you a variety of resistors. Every resistor has two leads, and it doesn't matter which way you insert a resistor into a circuit.

An LED flashlight circuit uses just three components and is probably the simplest circuit you'll ever build. It's easy to package that circuit in a case so that it looks like a finished product (well, sort of — "Foam flashlights for sale! Get 'em while they last!").But as your circuits get more complicated, you'll discover that it's not always wise to create a permanent, packaged circuit right off the bat.

Building a single LED circuit on a breadboard is a snap! Grab one 470 ohm resistor (yellow-violet-brown), any LED, your battery with battery clip, and needle-nose pliers. Then place your breadboard on a flat surface and follow these three steps:Insert an LED into the breadboard.Using your needle-nose pliers, gently bend the leads of the LED out and down, as shown.