Chapter 1

Introducing You to Electronics

IN THIS CHAPTER

Seeing electric current for what it really is

Recognizing the power of electrons

Using conductors to go with the flow (of electrons)

Pushing electrons around with voltage

Making the right connections with a circuit

Controlling the destiny of electrons with electronic components

Applying electrical energy to loads of things

If you're like most people, you probably have some idea about the topic of electronics. You've been up close and personal with lots of consumer electronics devices, such as smartphones, tablets, iPods, stereo equipment, personal computers, digital cameras, and televisions, but to you, they may seem like mysteriously magical boxes with buttons that respond to your every desire.

You know that underneath each sleek exterior lies an amazing assortment of tiny electronic parts connected in just the right way to make something happen. And now you want to understand how.

In this chapter, you find out that electrons moving in harmony through a conductor constitute electric current - and that controlling electric current is the basis of electronics. You discover what electric current really is and find out that you need voltage to keep the juice flowing. You also get an overview of some of the incredible things you can do with electronics.

Just What Is Electronics?

When you turn on a light in your home, you're connecting a source of electrical energy (usually supplied by your power company) to a light bulb in a complete path, known as an electrical circuit. If you add a dimmer or a timer to the light bulb circuit, you can control the operation of the light bulb in a more interesting way than just manually switching it on and off.

Electrical systems use electric current to power things such as light bulbs and kitchen appliances. Electronic systems take this a step further: They control the current, switching it on and off, changing its fluctuations, direction, and timing in various ways to accomplish a variety of functions, from dimming a light bulb (see Figure 1-1), to flashing your holiday light display in sync with your favorite holiday tune, to communicating via satellites - and lots of other things. This control distinguishes electronic systems from electrical systems.

FIGURE 1-1: The dimmer electronics in this circuit control the flow of electric current to the light bulb.

The word electronics describes both the field of study that focuses on the control of electrical energy and the physical systems (including circuits, components, and interconnections) that implement this control of electrical energy.

To understand what it means to control electric current, first you need a good working sense of what electric current really is and how it powers things such as light bulbs, speakers, and motors.

WHAT IS ELECTRICITY?

The term electricity is ambiguous, often contradictory, and can lead to confusion, even among scientists and teachers. Generally speaking, electricity has to do with how certain types of particles in nature interact with each other when in close proximity.

Rather than rely on the term electricity as you explore the field of electronics, you're better off using other, more precise, terminology to describe all things electric. Here are some of them:

• Electric charge: A fundamental property of certain particles that describes how they interact with each other. There are two types of electric charges: positive and negative. Particles of the same type (positive-positive or negative-negative) repel each other, and particles of the opposite type (positive-negative) attract each other.
• Electrical energy: A form of energy caused by the behavior of electrically charged particles. This is what you pay your electric company to supply.
• Electric current: The movement, or flow, of electrically charged particles. This connotation of electricity is probably the one you are most familiar with and the one I focus on in this book.

Checking Out Electric Current

Electric current, sometimes known as electricity (see the sidebar "What is electricity?"), is the movement in the same direction of microscopically small, electrically charged particles called electrons. So where exactly do you find electrons, and how do they move around? You'll find the answers by taking a peek inside the atom.

Exploring an atom

Atoms are the basic building blocks of everything in the universe, whether natural or manmade. They're so tiny that you'd find millions of them in a single speck of dust. Every atom contains the following types of subatomic particles:

• Protons carry a positive electric charge and exist inside the nucleus, or center, of the atom.
• Neutrons have no electric charge, and exist along with protons inside the nucleus.
• Electrons carry a negative electric charge and are located outside the nucleus in an electron cloud. Don't worry about exactly where the electrons of a particular atom are located. Just know that electrons whiz around outside the nucleus, and that some are closer to the nucleus than others.

The specific combination of protons, electrons, and neutrons in an atom defines the type of atom, and substances made up of just one type of atom are known as elements. (You may remember wrestling with the Periodic Table of the Elements way back in Chemistry class.) I show a simplistic representation of a helium atom in Figure 1-2 and one of a copper atom in Figure 1-3.

FIGURE 1-2: This helium atom consists of 2 protons and 2 neutrons in the nucleus with 2 electrons surrounding the nucleus.

FIGURE 1-3: A copper atom consists of 29 protons, 35 neutrons, and 29 electrons.

Getting a charge out of protons and electrons

Electric charge is a property of certain particles, such as electrons, protons, and quarks (yes, quarks) that describes how they interact with each other. There are two different types of electric charge, somewhat arbitrarily named positive and negative (much like the four cardinal directions are named north, south, east, and west). In general, particles carrying the same type of charge repel each other, whereas particles carrying opposite charges attract each other. Within each atom, the protons inside the nucleus attract the electrons that are outside the nucleus.

You can experience a similar attraction/repulsion phenomenon with magnets. If you place the north pole of a bar magnet near the south pole of a second bar magnet, you'll find that the magnets attract each other. If, instead, you place the north pole of one magnet near the north pole of another magnet, you'll observe that the magnets repel each other. This mini-experiment gives you some idea of what happens with protons and electrons - without requiring you to split an atom!

Under normal circumstances, every atom has an equal number of protons and electrons, and the atom is said to be electrically neutral. (Note that the helium atom has 2 protons and 2 electrons and that the copper atom has 29 of each.) The attractive force between the protons and electrons acts like invisible glue, holding the atom together, in much the same way that the gravitational force of the Earth keeps the moon within sight.

The electrons closest to the nucleus are held to the atom with a stronger force than the electrons farther from the nucleus; some atoms hold on to their outer electrons with a vengeance, while others are a bit more lax. Just how tightly certain atoms hold on to their electrons turns out to be important when it comes to electricity.

Identifying conductors and insulators

Materials (such as copper, silver, aluminum, and other metals) containing loosely bound outer electrons are called electrical conductors, or simply conductors. Copper is a good conductor because it contains a single loosely bound electron in the outermost reaches of its electron cloud. Materials that tend to keep their electrons close to home are classified as electrical insulators. Air, glass, paper, and plastic are good insulators, as are the rubber-like polymers that are used to insulate electrical wires.

In conductors, the outer electrons of each atom are bound so loosely that many of them break free and jump around from atom to atom. These free electrons are like sheep grazing on a hillside: They drift around aimlessly but don't move very far or in any particular direction. But if you give these free electrons a bit of a push in one direction, they will quickly get organized and move together in the direction of the push.

Mobilizing electrons to create current

Electric current (often called electricity) is the displacement of a large number of electrons in the same direction through a conductor when an external force (or push) is applied. That external force is known as voltage (which I describe in the next section, "Understanding Voltage").

This flow of electric current appears to happen instantaneously. That's because...