It did. They soon discovered that an electric current flowed from the heated filament to this third wire, and that the hotter the filament got, the more electric current flowed. This discovery, which came to be known as the Edison Effect, marks the beginning of technology known as electronics. The device, which Edison patented on November 15, 1883, is the world’s first electronic device.
When Edison patented his device in 1883, he had no idea what it would lead to. Now, nearly 140 years later, it’s hard to imagine a world without electronics. Electronic devices are everywhere. There are more television sets in the United States than there are people. No one uses film to take pictures anymore; cameras have become electronic devices. And you rarely see a teenager anymore without headphones in their ears.
Without electronics, life would be very different.
Have you ever wondered what makes these electronic devices tick? In this chapter, I lay some important groundwork that will help the rest of this book make sense. I examine the bits and pieces that make up the most common types of electronic devices, and take a look at the basic concept that underlies all of electronics: electricity.
I promise I won’t bore you too much with tedious or complicated physics concepts, but I must warn you from the start: In order to learn how electronics works at a level that will let you begin to design and build your own electronic devices, you need to have at least a basic idea of what electricity is. Not just what it does, but what it actually is. So put on your thinking cap and get started.
What Is Electricity?
Before you can understand even the simplest concepts of electronics, you must first understand what electricity is. After all, the whole purpose of electronics is to get electricity to do useful and interesting things.
The concept of electricity is both familiar and mysterious. We all know what electricity is or at least have a rough idea based on practical experience. In particular, consider these points:
We are very familiar with the electricity that flows through wires like water flows through a pipe. That electricity comes from power plants that burn coal, catch the wind, absorb sunlight, or harness nuclear reactions. It travels from the power plants to our houses in big cables hung high in the air or buried in the ground. Once it gets to our houses, it travels through wires through the walls until it gets to electrical outlets. From there, we plug in power cords to get the electricity into the electrical devices we depend on every day, such as ovens and toasters and vacuum cleaners.
We know, because the electric company bills us for it every month, that electricity isn’t free. If we don’t pay the bill, the electric company turns off our electricity. Thus, we know that electricity is valuable.
We know that electricity can be stored in batteries, which contain a limited amount of electricity that can be used up. When the batteries die, all their electricity is gone.
We know that some kinds of batteries, like the ones in our cellphones, are rechargeable, which means that when they’ve been drained of all their electricity, more electricity can be put back into them by plugging them into a charger, which transfers electricity from an electrical outlet into the battery. Rechargeable batteries can be filled and drained over and over again, but eventually they lose their ability to be recharged — and you have to replace them with new batteries. (Or, in the case of your iPhone, you have to buy a whole new phone.)
We also know that electricity is the stuff that makes lightning strike in a thunderstorm. In grade school, we were taught that Ben Franklin discovered this by conducting an experiment involving a kite and a key, which we should not attempt to repeat at home.
We know that electricity can be measured in volts. Household electricity is 120 volts (abbreviated 120 V). Flashlight batteries are 1.5 volts. Car batteries are 12 volts.
We also know that electricity can be measured in watts. Traditional incandescent light bulbs are typically 60, 75, or 100 watts (abbreviated 100 W). Microwave ovens and hair dryers are 1,000 or 1,200 watts. The more watts, the brighter the light or the faster your pizza reheats and your hair dries.
Except that we also know that some technologies do more work for a given wattage. Thus, a 20-watt CFL bulb and a 12-watt LED bulb both produce as much light as a 75-watt incandescent bulb.
We also may know that there’s a third way to measure electricity, called amps. A typical household electrical outlet is 15 amps (abbreviated 15 A).
The truth is, most of us don’t really know the difference between volts, watts, and amps. (Don’t worry; by the time you finish Chapter 2 of this minibook, you will!)
We know that there’s a special kind of electricity called static electricity that just sort of hangs around in the air but can be transferred to us by dragging our feet on a carpet, rubbing a balloon against our hairy arms, or forgetting to put an antistatic sheet in the dryer. And finally, we know that electricity can be very dangerous. In fact, dangerous enough that for almost 100 years electricity was used to administer the death penalty. Every year, hundreds of people die in the United States from accidental electrocutions.
But Really, What Is Electricity?
In the previous section, I list several ideas most of us have about electricity based on everyday experience. But the reality of electricity is something very different. Chapter 2 of this minibook is devoted to a deeper look at the nature of electricity, but for the purposes of this chapter, I want to start by introducing you to three very basic concepts of electricity: namely, electric charge, electric current, and electric circuit.
Electric charge refers to a fundamental property of matter that even physicists as smart as Neil deGrasse Tyson don’t totally understand. Suffice it to say that two of the tiny particles that make up atoms — protons and electrons — are the bearers of electric charge. There are two types of charge: positive and negative. Protons have positive charge, electrons have negative charge.Electric charge is one of the basic forces of nature that hold the universe together. Positive and negative charges are irresistibly attracted to each other. Thus, the attraction of negatively charged electrons to positively charged protons hold atoms together.If an atom has the same number of protons as it has electrons, the positive charge of the protons balances out the negative charge of the electrons, and the atom itself has no overall charge.However, if an atom loses one of its electrons, the atom will have an extra proton, which gives the atom a net positive charge. When an atom has a net positive charge, it goes looking for an electron to restore its balanced charge.Similarly, if an atom somehow picks up an extra electron, the atom has a net negative charge. When this happens, the atom goes looking for a way to get rid of the extra electron to once again restore balance. Okay, technically, atoms don’t really go “looking” for anything. They don’t have eyes, and they don’t have minds that are troubled when they’re short an electron or have a few too many. However, the natural attraction of negative to positive charges causes atoms that are short an electron to be attracted to atoms that are long an electron. When they find each other, something almost magic happens… . The atom with the extra electron gives its electron to the atom that’s missing an electron. Thus, the charge represented by the electron moves from one atom to another, which brings us to the second important concept …
Electric current refers to the flow of the electric charge carried by electrons as they jump from atom to atom. Electric current is a very familiar concept: When you turn on a light switch, electric current flows from the switch through the wire to the light, and the room is instantly illuminated.Electric current flows more easily in some