In Part 2 of this mini magnum opus, we introduced the concepts of voltage (V), current (I), and resistance using a water analogy (we also extended our analogy to introduce the concept of charge). Now it’s time to delve a little deeper into the way in which electricity works.
Protons, Neutrons, Electrons, and Atoms
Before we proceed, we first need to understand just a little bit about how the universe works. All of the physical objects we see around us -- tables, chairs, houses, clothes, animals, people, and cheese (I like cheese) -- are formed from teeny-tiny particles that are so small they can only be seen by scientists using very special equipment.
The three types of particles we're interested in here are called protons, neutrons, and electrons. I tend to think of protons and neutrons as being the equivalent of big, ponderous, lethargic adults who tend to sit on the sofa chatting about how much harder life used to be when they were young. By comparison, electrons make me think of small, boisterous, energetic kids racing around and around making nuisances of themselves.
Protons are relatively large, and each proton carries a single positive (+ve) charge. By comparison, electrons are really, really small; even so, each electron carries a single negative (-ve) charge that is the exact opposite of a proton's positive charge. Last, but certainly not least, neutrons are pretty much the same size as protons, but they are electrically neutral, which means they don’t carry any charge at all.
Do you remember playing with bar magnets at school? Each magnet has a north pole at one end and a south pole at the other. When the magnet is freely suspended, its north pole is the one that ends up pointing towards the Earth's North Magnetic Pole in the Artic. One of the interesting things you may recall is that the north pole of one magnet will attract the south pole of the other, and vice versa. However, their north poles will repel each other, as will their south poles.
Well, something similar happens with protons and electrons. A proton and an electron will be attracted to each other, but two protons will repel each other, as will two electrons. Of course, being electrically neutral, neutrons could “care less,” as they say.
One very important point to note is that, unlike bar magnets, protons and electrons never actually touch each other. Instead, the electron races round and round its adopted proton like a frisky little dog on a leash running around and around its owner's feet.
Protons, neutrons, and electrons don’t really like their own company and they aren’t particularly happy if they are left on their own. Instead, they are sociable little fellows who like to gather together to form groups that we call atoms. The protons and neutrons form a tight ball called the nucleus in the center of the atom, while the electrons zip round and round some distance from the nucleus. One way to visualize this is that electrons orbit the nucleus of an atom in the same way that planets orbit the Sun.
Now, remembering that two or more protons will repel each other, you might wonder how they manage to keep company in the nucleus. The answer is the amiable old neutrons, which act like glue and hold everything together.
As illustrated below, the number of protons determines the type of the atom. Also, by default, each proton in an atom has a corresponding electron, thereby leaving the atom electrically balanced. There may be slightly different flavors of each atom based on the number of neutrons (these flavors are called isotopes). For example, a hydrogen atom has one proton and one electron. The most common form of hydrogen doesn’t have any neutrons, but there are isotopes with one or two neutrons.
Meanwhile, a helium atom has two protons, two electrons, and two neutrons; a lithium atom has three protons, three electrons, and four neutrons; a beryllium atom has four protons, four electrons, and five neutrons; and so on.
The term “element” refers to a substance that is composed entirely from one type of atom. There are close to 100 naturally occurring elements*, including things like oxygen, carbon, silicon, iron, copper, and gold. (*The actual number depends on who you are talking to, how they classify things, and whether you limit yourself to elements that can be found on Earth, or if you also include elements that can be found somewhere in the universe.) In addition to the naturally occurring elements, there are also 24 or more synthetic elements that scientists have created in their laboratories (the reason I say "or more" is that you never know what those tricky scientists will get up to next).
Different mixtures of these elements can be combined to form an almost infinite number of materials, resulting in everything from inanimate things like rocks and glass, to interesting things like bacon sandwiches and ice cream (I like both, but not mixed together), to living creatures like you and me.
In my next column, we’ll consider how we can use our knowledge of atoms to create things like batteries, and how we can then use these batteries to power our electrical and electronic circuits. Until then, as always, I welcome your comments and questions.