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Hello, and welcome to Advent Science 2011, the pewterfish edition. This is a little experiment being performed by myself, pufferfish and duckbunny: we rather suspect we can teach our readership something interesting in the month of December, and we've each chosen a subject we know fairly well. It's kind of like an advent calendar, but each door conceals awesome knowledge instead of chocolate or paintings or Lego. Not that such things are bad, of course.
Pufferfish is talking about genetics, and duckbunny about the history of the atmosphere. In the next 24 days, I hope to lead you on a journey from science to engineering, and beyond, in one very narrow field.
Computers are everywhere these days, on our desks, in our pockets, in the back rooms behind companies like Google, and Facebook, and Oracle. They cook our food, wash our clothes, and guide our aircraft. But to many people, the computer is a magic box, a Thing within which humankind is not meant to peer.
That's nonsense. They're machines, just like everything else, the parts are just smaller and less obvious in function. I happen to know my way around them quite well, so I'm going to impart some of that knowledge to you, if you keep reading. I'll necessarily have to gloss over details from time to time, but I mean to touch everything important, and leave a trail of links for you to follow if you want to learn more.
Join me, then, as we wander from Electrons, to Email.
If we're going to go from Electrons to Email, I guess we'd better start at the beginning. Time for some particle physics.
The electron is a particle with a unit negative charge. That is, it is a particle with the smallest negative electrical charge known to exist - there's no such thing as "half an electron's worth of charge". An atom consists of protons and neutrons in the nucleus, and orbiting electrons: a proton has a unit positive charge, an uncharged atom has an equal number of protons in the nucleus as it has electrons orbiting it.
Opposites attract, as well we all know, and electrons are no different. Electrons, being negative, are drawn towards positively charged objects. But what's charge? It's the presence or absence of "the right number" of electrons. When I said that an uncharged atom has an equal number of electrons and protons a paragraph ago, I didn't mention what happened if the numbers weren't equal. If an atom has less electrons than protons, it is positively charged. If it has more, it is negatively charged. A charged atom is called an ion. Positive ions "want to" gain electrons, and achieve neutrality. Negative ions "want to" lose electrons. I put "want to" in quotes because there is, of course, no desire involved. Equally, it's not something I can easily explain without going deeper into partical physics than I really want to, so you kind of have to accept it.
Electrons are drawn to positively charged objects, and repelled by negatively charged objects. This is as true at the macroscopic level as it is at the atomic: a positive electrode will attract electrons, and negatively charged objects, to itself.
It follows that given a difference in charge, electrons will tend to flow from a negatively-charged object to a positively charged object, until the charges are equalised. This flow is called electricity. The chemical reactions within an AA battery cause one end to become more positive and the other more negative as they proceed, and it is possible to extract energy to light lamps, sound buzzers and so on by placing the item to be powered between the positive and negative ends: the electrons flow and, on their way, they power the item. Given enough time, the chemical reactions within the battery will cease as their fuel is consumed and the electrons will slowly drift back to equal out across the battery - this is what happens when a battery is discharged, or "flat".
The difference in charge between two objects is called the Voltage, or potential difference, that exists between them. The number of electrons per unit of time that flow between them is called the Current. Current is measured in Amperes, or "amps", and a single ampere is 6.241x10^18 electrons per second.
Given that that's an awful lot of electrons (roughly six quintillion), it should come as no surprise that in electronics, it is normal to deal with thousandths or millionths of an amp, or even smaller amounts.
So, that's the electron, more or less. I've glossed over some bits, because down at the tiny tiny scale of particle physics, it can be a bit too easy to get sucked down the rabbithole of detail, but that's enough that I can explain the next bit with. See you tomorrow.
For more in-depth information...
2011/12/02 - Craig (08:38)
Awesome idea sir's. As I see it I get the best of both worlds, a little bit of chocolate and a little bit of knowledge.
Although no mention of (if only for the name) gluons? *sadface*