An electric circuit is a closed loop made of conductors and other electrical elements through which electric current can flow. For example, Figure 1-2 shows a very simple electrical circuit that consists of three elements: a battery, a lamp, and an electrical wire that connects the two.The circuit shown in Figure 1-2 is, as I already said, very simple. Circuits can get much more complex, consisting of dozens, hundreds, or even thousands or millions of separate components, all connected with conductors in precisely orchestrated ways so that each component can do its bit to contribute to the overall purpose of the circuit. But all circuits must obey the basic principle of a closed loop. All circuits must create a closed loop that provides a complete path from the source of voltage (in this case, the battery) through the various components that make up the circuit (in this case, the lamp) and back to the source (again, the battery).
FIGURE 1-1: An insulated wire consists of a conductor surrounded by an insulator.
FIGURE 1-2: A simple electrical circuit consisting of a battery, a lamp, and some wire.
What Is Electronics?
One of the reasons I started this chapter with the history lesson about Thomas Edison was to point out that when the whole field of electronics was invented in 1883, electrical devices had already been around for at least 100 years. For example:
Benjamin Franklin was flying kites in thunderstorms more than 100 years before.
The first electric batteries were invented by a fellow named Alessandro Volta in 1800. Volta’s contribution is so important that the common term volt is named for him. (There is some archeological evidence that the ancient Parthian Empire may have invented the electric battery in the second century BC, but if so we don’t know what they used their batteries for, and their invention was forgotten for 2,000 years.)
The electric telegraph was invented in the 1830s and popularized in America by Samuel Morse, who invented the famous Morse code used to encode the alphabet and numerals into a series of short and long clicks that could be transmitted via telegraph. In 1866, a telegraph cable was laid across the Atlantic Ocean, allowing instantaneous communication between the United States and Europe.
Contrary to popular belief, Benjamin Franklin wasn’t the first to fly a kite in a thunderstorm. In 1752, he published a paper outlining his idea. Then he let a few other people try it first. After they survived, he tried the experiment himself and wound up getting all the credit. Benjamin Franklin was not only very smart; he was also very wise.
All of these devices and many other common devices still in use today, such as light bulbs, vacuum cleaners, and toasters, are known as electrical devices. So what exactly is the difference between electrical devices and electronic devices?
The answer lies in how devices manipulate electricity to do their work. Electrical devices take the energy of electric current and transform it in simple ways into some other form of energy — most often light, heat, or motion. For example, light bulbs turn electrical energy into light so that you can stay up late at night reading this book. The heating elements in a toaster turn electrical energy into heat so that you can burn your toast. And the motor in your vacuum cleaner turns electrical energy into motion that drives a pump that sucks the burnt toast crumbs out of your carpet.
In contrast, electronic devices do much more. Instead of just converting electrical energy into heat, light, or motion, electronic devices are designed to manipulate the electrical current itself to coax it into doing interesting and useful things.
That very first electronic device invented in 1883 by Thomas Edison manipulated the electric current passing through a light bulb in a way that let Edison create a device that could monitor the voltage being provided to an electrical circuit and automatically increase or decrease the voltage if it became too low or too high.
One of the most common things that electronic devices do is manipulate electric current in a way that adds meaningful information to the current. For example, audio electronic devices add sound information to an electric current so that you can listen to music or talk on a cellphone. And video devices add images to an electric current so you can watch great movies like Office Space, Ferris Bueller’s Day Off, or The Princess Bride over and over again until you know every line by heart.
Keep in mind that the distinction between electric and electronic devices is a bit blurry. What used to be simple electrical devices now often include some electronic components in them. For example, your toaster may contain an electronic thermostat that attempts to keep the heat at just the right temperature to make perfect toast. (It will probably still burn your toast, but at least it tries not to.) And even the most complicated electronic devices have simple electrical components in them. For example, although your TV remote control is a pretty complicated little electronic device, it contains batteries, which are simple electrical devices.
What Can You Do with Electronics?
The amazing thing about electronics is that it’s being used today to do things that weren’t even imaginable just a few years ago. And of course, that means that in just a few years we’ll have electronic devices that haven’t even been thought up yet.
That being said, the following sections give a very brief overview of some of the basic things you can do with electronics.
Making noise
One of the most common applications for electronics is making noise. Often in the form of music, though the distinction between noise and music is often debatable. Electronic devices that make noise are often referred to as audio devices. These devices convert sound waves to electrical current, and then store, amplify, and otherwise manipulate the current, and eventually convert the current back to sound waves you can hear.
Most audio devices have these three parts:
A source, which is the input into the system. The source can be a microphone, which is a device that converts sound waves into an electrical signal. The subtle fluctuations in the sound waves are translated into subtle fluctuations in the electrical signal. Thus, the electrical signal that comes from the source contains audio information.The source may also be a recorded form of the sound, such as sound recorded on a CD or in an MP3.
An amplifier, which converts the small electrical signal that comes from the source into a much larger electrical signal that, when sent to the speaker or headphones, can be heard.Some amplifiers are