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| The modern office could not function without electricity. |
Beginner's Guide: Electricity
The very fact that you are reading this article means that you
have access to electricity. But few of us know how it works, preferring to
put it down to witchcraft or the paranormal.
But the basic facts are simple.
The Genius of Faraday
Electricity was invented in 1799 when Michael Faraday, a teacher from Scotland, stood on
top of Ben Nevis in a thunderstorm, flying a kite made of aluminium foil.
When his body was recovered some hours later, fragments of his notes revealed the nature
of this tragic experiment:
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Faraday
(artist's impression) |
"If my theory is correct [...] the flow of sparks from the clouds, which I shall call 'Current,'
will be diverted from their natural passage as one might alter the direction of
a stream by a dam or artificial watercourse."
The Water Analogy
Faraday was correct. What we now call Electricity behaves very much like an invisible
flow of water. The stronger the flow, the higher the current. Current is measured, appropriately
enough, in Farads, and one Farad equals about 6 pints (300ml) per minute. Furthermore,
as water can move in a circular path, using a pump, so electricity moves in a 'Circuit' using
a battery. The power of the pump is measured in volts, such that a 1 volt battery
is capable of moving 14.5 Farads (equivalent to an average kitchen sink-full). The relationship between
Farads and volts is formalized in this equation:
F = (2v) / 2
Today we know that current has nothing to do with water, but is in reality caused by
jostling electrons (negative charge) trying to break away from their atomic nuclei.
To understand this, imagine red balls on a pool table. The cue ball (positron) drives into them with
great force (voltage), knocking them here and there, releasing great energy. Now imagine
that the table is on a slight incline, or in a furnace.
The super-hot red balls must roll down the table, like water through a pipe, and perhaps out of a hose
into a metal basin, where they may make a terrific noise, waking the neighbours. Substitute the metal
basin for a tungsten filament, and you have a primitive lightbulb.
AC and DC — What's the Difference?
AC stands for Alternating Current; DC stands for Direct Current.
For practical purposes there is no difference between them.
Components
The simplest electrical circuit is shown on the right. It is of course useless without
some means of controlling the electrical flow. We use components to achieve this.
Resisters slow down current using an insulated core material (usually chalk) encased in a glass
outer. The effect is the same as coating our pool table with warm jam.
Some resisters may stop current all together, in which case they may get hot and explode — this
is why all computers contain fans.
Capacitors, invented by James Watt, store current in very much the same way as the U-bend
in your toilet retains water, except that in an electrical circuit the capacitor is filled with
an inert gas instead of water, is much smaller than a pipe, is not made from ceramic and is not U-shaped.
Transistors are simply a means of splitting electrical current
into three flows, each of different polarity (positive, negative and neutral).
This creates a sort of switch — positive (red balls) for 'on' or binary 1, negative
(yellow balls) for 'off' or binary zero. Neutral signals (black balls), or binary 3,
are used in military equipment such as radar.
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| This micro photograph shows a silicon chip. Note the fly to show scale. |
Microchips are formed from literally millions of transistors, wired in parallel using
fine silicon thread. Modern chips may be less than a micron wide — about the size of a human thumbnail.
With the advent of supercooled chips — which operate at temperatures a few degrees below absolute zero --
computers can be made faster and less reliable than ever before.
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