Things Left Out of Other Books on Basic Electronics (c) 2000
Basic Electronics for the Gaming Industry
Atoms, Molecules and Electronics
Bear in mind that this a simplified discussion of the elements. Reality is a bit
more complicated. Our intention here is the study of the behavior of electrons. This study
we call electronics. This is a very condensed course. In a college we might spend a month
on this subject. In a technical school we might spend a week. Here we are going to spend
about one hour. College is certainly a better education. A technical school (like a Slot
Tech School) would be second best. This is intended to cover only the minimal
knowledge acceptable to learn basic concepts and is not intended to cover everything you
might get in a Technical School or College.
Defining atoms (that define an element) and molecules (that define a compound)
Everything around us that has substance is made of atoms. If we take a chunk of
Aluminum and start breaking it apart into smaller and smaller pieces, the smallest thing
we could break it into, and still have something identifiable as Aluminum, would be an
atom of Aluminum. All atoms of Aluminum are identical in size and structure. We can
not break Aluminum down into any other identifiable materials. This makes Aluminum a
basic element.
We have identified about one hundred basic elements that make up everything
around us. Water, for instance, is made of Hydrogen and Oxygen. If we take water apart
into smaller and smaller units. The smallest unit that would be identifiable as water
would be a group of two atoms of Hydrogen and one atom of Oxygen, designated H2O.
This is one molecule of water. These substances are called compounds.
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Various useful pictures have been conceived over the years to describe what an
atom looks like. Before Einstein's time the atom was thought of as a raisin muffin, with
the electrons being as raisins on a hard, solid, muffin. Most text books with such pictures
have long passed out of use. In older texts we might find drawings of Rutherford's
concept of an atom.
Rutherford's concept of the atom
To Rutherford the electrons formed in layers like onion skins. The electrons
formed in groups of shells and subshells, each with a predictable maximum number of
electrons per shell and subshell.
Most newer texts describe a Quantum Theory concept of the atom.
(Quantum Theory atom)
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The primary difference is that the electrons do not orbit in nice spherical shells.
The first shell (as in Hydrogen) may be spherical, but as we add another (Helium) the two
electrons react against one another. Being magnetic in nature, the bodies with like
polarity repel one another and opposites attract. The negative electrons are being repelled
from one another and tend to stay in a pear-shaped area with the narrow end centered
around the nucleus. The two electrons stay oppoosite one another with the two lobes
making a peanut-shape. At the same time the electrons are being attracted toward the
positively charged protons in the nucleus. If we add a third electron (making Lithium) the
third electron would form a donut-shaped orbit around the middle of the peanut.
The protons in the nucleus are being repeled from one another, but at the same
time being held in the confines of the nucleus by a "Strong Force". This "Strong Force"
also repells the electrons, keeping the electrons in confined territories. The whole of the
atom is an interplay of forces of energies. The shells and subshells of the Rutherford
model are kept to some degree. Experiments bear support to these theories, but none
should be considered to be the whole truth as yet.
We look back at the raisin muffin idea of a hundred years ago and smile. It is safe
to assume that the theories will be refined and people will look back at the quantum
theory a hundred years from now smile the same way.
Atoms and molecules are the smallest identifiable objects we can identify.
Molecules break down into atoms, but once we break an atom apart we cease to have
anything we can identify as a substance. Sub-atomic particles are primarily just globs of
energy.
All atoms are made of a central core, called a nucleus, surrounded by a shell of
electrons. Electrons from an Aluminum atom are the same as electrons from Hydrogen or
Oxygen atoms.
The nucleus is made of Protons and Neutrons. All protons are identical. All
Neutrons are identical. Around this central core is layers of electrons flyiing around in
what can best be described as orbits. The only thing that makes Aluminum different from
Oxygen or Hydrogen is the number of Electrons, Protons, and Neutrons that make up the
atoms.
Hydrogen, for example, is the most basic element. An atom of Hydrogen has a
nucleus of one proton with one electron circling around it. All hydrogen atoms are made
this way, and everything made this way must be hydrogen.
The next heaviest element is Helium, which has two protons in the nucleus,
surrounded by two electrons. All helium atoms are made this way, and everything made
this way must be helium.
All elements can be referred to by their structural makeup. Hydrogen has just one
proton, so it is given the Atomic Number “1”. It has only one proton in it’s nucleus, so it
given the Atomic Weight of “1”. There are always (normally) an equal number of
electrons as there are protons. Helium has an Atomic Number of “2”, having two protons.
Helium has an Atomic Weight of “4”. The nucleus of Helium has two protons and
Two neutrons, the sum of the parts in the nucleus is what defines the Atomic Weight.
Every element has a unique Atomic Number and Atomic Weight. This is not a perfect
reality. Every element also has variations of it that may have more or less neutrons in the
nucleus than the norm would be. These are called isotopes of that element.
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The Atomic number covers a range from one to over one hundred, but atomic
diameter varies much less. Hydrogen, the smallest of the elements. At STPG (Standard
Temperature Pressure and Gravity) Hydrogen has a diameter of 0.53 Angstroms.
Francium, the largest element I have data for, with an atomic number of 87 only has a
diameter of 2.7 Angstroms. Only five times the diameter of Hydrogen. (*)
Almost all of the mass of an atom is in the nucleus. An electron is about the same
size as a proton or neutron, if you can imagine a cloud having a physical size. But the
electron has only about 1/1800th the mass of a proton or neutron.
Electrons have a negative electrostatic charge. Protons have a positive
electrostatic charge. It is this electrostatic charge that we will spend some time
discussing. Neutrons are neutral, and have no charge, and play no part in our study of
Electricity. An electron is mostly electromagnetic energy and it is the study of the
behavior of electrons we will primarily concern ourselves with.
The normal atom, having an equal number of negative electrons and positive
protons, has no electrical charge. It is this characteristic we will alter as we discuss
electricity. If we remove an electron from an atom, it now has more positively charged
protons than negatively charged electrons, and the atom becomes a positive ion, a
charged atom. Likewise, if we force an extra electron onto an atom it now has more
electrons than protons, and becomes a negative ion.
For our purposes, we are concerned with the outer shell of electrons. An electron
is mostly energy with very little mass. Electrons move around the nucleus is loosely
defined shells at extremely high speeds (186,000 miles per second, or 300,000 kilometers
per second). The structure of these shells defines many characteristics the element will
have.
The electrons are layered in predictable shells and subshells. It is the outer shell,
called the Valence Shell, of electrons that is of particular interest to us in the study of
electricity. If the outer shell has only one or two electrons, they may be pulled away and
move to a neighboring atom with relative ease. This is what makes an element a good
conductor of electricity. These are primarily metals.
If the outer shell is complete and stable (with eight eectrons), the electrons are not
readily pulled out of place. These elements are insulators, and do not conduct electricity
well.
These last two statements are true whether we are talking about an element or a
molecule. If a molecule has one or two loosely bonded electrons, it will be a good
conductor. If not, it will be a good insulator.
In between the extremes of conductors and insulators are a group of elements (or
molecules) that have four or five electrons in the outer shell. These are semiconductors.
They are neither good conductors, nor good insulators. By controlling the specific
characteristics of these elements we can get some very creative results. This is the realm
of Solid State Electronics.
Conductors, like metals, are used to carry electricity from one point to another.
Insulators are used to prevent the flow of electricity where we don't want it to go.
Semiconductors are used to specifically manipulate the flow of electricity in detail.
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Some popular semiconductors are elements like Carbon, Selenium, Silicon, and
Germanium, or compounds like Cadmium Sulfide, and Gallium Arsenide. The list of
useful molecular compounds is extensive. By including various elements, we can get
unique characteristics that cause light to be emitted (Gallium Arsenic, or Gallium Arsenic
Phosphide), or cause the compound to react to the presence of light (Cadmium Sulfide).
We can create substances that change shape on the application of electricity, or create
electricity by the application of physical pressure.
What we have said concerning what makes an atom a conductor or insulator also
applies to molecules. While a metal, like Iron, mixes with Oxygen to make iron oxide,
the result is an insulator. The outer electrons of the Iron atoms are tied up in bonds to the
Oxygen atoms. Rust (iron oxide) is a poor conductor.
The possibilities are limited only by the laws of physics, our understanding of the
elements and the imagination we apply in manipulating the laws of physics.
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Things Left Out of Other Books on Basic Electronics (c) 2000
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Electricity and Electronics
Electricity is the flow of electrons, and the accompanying things that happen
when an electron moves through a conductor. Electronics is the detailed study of how
electrons flow, and all the wonderful things that happen in solid state physics.
Current, Voltage, and Resistance.
The Intensity of current flow (I) is measured in Amps (Amperes). This is a
measure of how many electrons are in motion at any specific point in a circuit.
The electrical pressure pushing the electrons through a circuit is measured in
Volts. This is sometimes called Electromotive Force (EMF), because that is a good
description of what it is - the force that moves the electrons.
Normally, in an atom, we have an equal number of electrons and protons. The
electrical charge of the atom is neutral. When an electron is pulled away from an atom, it
leaves a tension in the atom. The atom now has a positive charge (from the missing
electron). This tension is the source of pressure we call voltage. This positively charged
atom sucks at the nearby environment, attracting an electron, causing current to flow.
The opposition to current flow is Resistance. Resistance is measured in Ohms. As
we mentioned, some elements require more pressure before we can get an electron to cut
loose from its bond to the atom. The harder it is to pull an electron away, the more
resistance the material has.
(The following analogy between water flow and electron flow is useful in learning
the basic concepts, but be mindful that this analogy develops flaws as you get into the
finer details of solid state electronics.)
Current, Voltage, and Resistance can be visualized as water flowing through a
pipe. The larger the pipe is, the easier water can flow through the pipe. More water can be
carried through a larger pipe. Likewise, larger wire is required to carry higher current
levels.
The pressure pushing water through the pipe is analogous to the voltage applied in
a circuit. By exerting more pressure, higher current can be caused to flow through a given
circuit. For higher pressures, thicker pipes, or pipes of stronger material, are required.
Likewise, higher voltage requires insulators of high resistance, or thicker material.
The opposition to the flow of water through a pipe is analogous to electrical
resistance. Thinner pipe resists the flow of large amounts of water. Smaller wire has a
higher resistance than larger wire. A pipe with a filter, or blockage, inhibits water flow.
Semiconductors, such as carbon or metal oxides, resist current flow and allow us to tailor
the current flow to a specific desirable value.
In a conductor the electrons in the outer shell of the atoms (called the Valence
shell) are in constant motion, but moving in no particular order. As one of the loose
electrons (called Valence electrons) moves from one atom towards another, the atom also
attracts an electron from another neighboring atom onto the atom it just left, and pushes
an electron off of the atom it is moving to.
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We can look at a voltage from either point of view; a negative voltage pushing
electrons; or a positive voltage sucking electrons. The difference is only relative. Voltage
is a difference of a potential to move electrons between two points in a circuit.
A conductor can be looked at as having a Sea of Electrons available to allow
current flow. All we have to do is apply pressure to get current to flow in the direction we
choose. Getting back to our analogy to water. We can view a glass of water, full to the
brim, as a conductor. If left alone the water molecules can move aimlessly around in the
glass, but no organized flow is apparent. When we add pressure to the water by inserting
our finger into the glass, water flows out of the glass in proportion to the force and
volume we exert.
Polarity
As mentioned before, electrons have a negative charge. As we insert an electron
into a conductor, it repels a neighboring electron, which pushes on this sea of electrons.
Almost instantly, on the opposite end of the conductor, another electron is forced out.
This force moves down the wire at the speed of light, 186,000 miles per second, or
300,000 kilometers per second, if you prefer.
A force that pushes electrons is called Negative. A force that attracts an electron
is called Positive. To have current flow we have to a difference of potential force between
two places in a circuit. Electrons flow from a Negative voltage to a Positive voltage.
Negative and Positive need only be of relative values.
How we view current flow can be viewed from two perspectives. We can say
electrons flow from negative to positive, and be quite correct. For every electron that
moves from negative to positive, we have a hole where that electron was that sucks in a
neighboring electron. If we view the electron as moving from left to right through a line
of electrons, we can also allow the point of view that a hole moves from right to left.
Conventional current flow (hole flow) can be said to move from positive to negative.
If you learn electricity in a chemistry or physics class, you were probably taught
that electricity flows from positive to negative. Such was the story when Ben Franklin
flew his kite. As we got into the twentieth century and discovered what was inside the
atom, the concept of the electron changes our opinion of what electricity was.
We must understand that both of these are happening at the same time, it is only a
matter of how we look at what is happening. If we take a bottle of water with a narrow
neck and dump it into a sink do you see bubbles flowing upwards or water flowing
downward? One can not happen without the other. Such is current flow. Whether you
look at it as electrons (negative charges) flowing from negative to positive, or holes
(positive charges) flowing from positive to negative makes no difference. When we get to
solid state devices, you must consider and understand both concepts.
Another important concept is that negative and positive can only be relative
differences. Rivers flow down hill. It doesn't matter how high, with respect to sea level,
the higher level is. Gravity (our voltage) causes the water to flow from a higher level to a
lower level (our current flow) hampered only by the terrain (our resistance) over a path
we can manipulate (our circuit).
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Magnetism
The electron is little more than a small packet of electromagnetic energy. A
characteristic we have not mentioned so far is magnetism. When electrons move through
a conductor a magnetic field builds up around the conductor. This magnetic field is
present in the conductor all the time. With no voltage applied the movement of the
electrons is random. One field cancels out another, and there is no discernable field
present.
When we apply a voltage to a conductor, the flow of the electrons is orderly, and
the magnetic fields add to one another. A magnetic field builds up around the wire.
Another phenomenon worth mentioning; when a magnetic field crosses a wire, it
induces a voltage in the wire causing current to flow through the wire. As long as there is
relative motion between the wire and the magnetic field, we generate a voltage in the
wire.
If we rotate a permanent magnet around coil of wire we can generate electricity
(like a generator or alternator in a car). If we move electricity through a coil of wire
around a magnet (or magnetic material) we can cause motion to occur (as in a motor).
If we take one coil of wire and wrap it around another coil of wire we can change
the level of the voltage by selecting how many turns of wire are in each coil. This is
called a transformer.
DC, AC and Frequency
The circumstance we have described so far is a very simplified concept of a
circuit. We have two wires with a voltage across them, and are trying to take a close look
at what happens when the two wires come in contact with one another, or are connected
across something.
Our electrons flow from the more negative wire, through the "load" (consider it a
light bulb) and toward the more positive wire. This is Direct Current (DC). Our electricity
only flows in one direction, negative wire to positive wire. The Negative wire is always
negative and the Positive wire is always positive. We can vary the magnitude of how
much current is flowing, but it always flows in the same direction between the wires, and
at the same speed.
For purpose of description only, we will say that the wire in our left hand is
negative, and the wire in our right hand is positive. Electrons flow out of the wire in our
left hand, through the lamp, and into the wire in our right hand. In Alternating Current
(AC) first one wire is negative, and the other positive, then it alternates. The wire in our
right hand becomes negative, and the one in our left hand becomes positive. Electrons
flow from the wire in our right hand, through the lamp, and into the wire in our left hand.
The electrons flow back and forth through the lamp in alternating directions.
How fast the current changes direction is the frequency, in Cycles per Second, or
more commonly called Hertz (Hz). The power coming out of our wall socket is 50, 60, or
400 Hz, depending on what country you live in. The electricity comes out of the wire in
our left hand, through the lamp, into the wire in our right hand, then out of the wire in our
right hand, through the lamp, and into the wire in our left hand, 50, 60, or 400 times per
second. (Don't take me literally and try to hold the wires in your hands. The voltage
coming out of the wall is of high enough voltage to be lethal.)
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Even in AC, the electrons are still flowing from negative to positive. It is the
polarity of the wire that is changing. First the wire in your left hand is negative and the
right positive. Then the wire in your right hand is negative and your left positive.
The frequency is an important factor to us. To give you some idea of typical
frequencies;
DC to a few dozen Hz - Subsonic range. At this frequency we have the nervous
systems of animals and other biologics like plants.
A few dozen Hz to about 15,000 Hz - Sonic range we can hear. If we were to
translate the changes in the electromagnetic fields into sound, these frequencies we could
hear. You will hear the sound when you get shocked also. Some of us know very well
what 60 Hz sounds like. It is not suggested that you attempt to experience this first hand.
About 15,000 Hz up to about 100,000 Hz - Ultrasonic range. Animals with
smaller ears can hear higher frequencies. As implied above these electronic signals must
be converted to achnges in air pressure to be heard.
530,000 Hz to 1,710,000 Hz - AM radio (US). At these frequencies, and higher,
our electromagnetic fied will propogate as an electromagnetic wave.
87,500,000 to 108,000,000 Hz - FM radio (US)
Television channels go up to a few hundred million Hz.
Microwave channels go from many hundred millions of Hz to trillions of Hz.
Currently, the top range of what frequency we can generate in electronics is
around 150 GHz (Giga Hertz, one Giga is a thousand millions).
This is the short story, by all means. There is much more to it than what we have
covered here. This is supposed to be basics.
(To keep the subject up to date, if we remove a neutron from the strong forces at the center of an
atom, the neutron decays into a proton, an electron, an anti-neutrino, and energy. So, in a sense, we can say
that an atom is actually only made of electrons and protons. Protons and neutrons are made of even smaller
units, called quarks, but are not readily separated. Quarks come in various colors and flavors that use a
language English is at a loss to explain. The words are just not available to uniquely describe sub-atomic
particles and energies. There is considerably more to this concept, but it is of little importance to us on this
subject and at this time.)
Notes, just for the heck of it.
(*)
The size of the atoms does not evenly increase as the atomic number increases. There are a
handful of rules that govern the size of the atom. If we were to graph to atomic radius with the atomic
number you would find that the atoms increase in size atomic diameter peaks and falls six times. For
instance, looking at the first twenty-five elements, we find a peak at lithium (atomic number = 3), Sodium
(atomic number = 11), and potassium (atomic number = 19). In all these cases the peak coincides with the
new electron starting a new shell (Valence = 1). As more electrons (and protons) are added to make heavier
elements, the diameter of the atom actually decreases until the last outer shell is completed. Starting a new
shell causes the diameter to peak again.
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1)
An atom is made of an inner nucleus of ______________ charged Protons and
neutrally charged Neutrons, with an outer shell of _________________ charged
Electrons. The protons and neutrons are mostly matter and make up most of the mass of
the atom.
2)
If the outer shell has only one or two electrons, the outer electrons may be pulled
away and move to a neighboring atom with relative ease. This is what makes an element
a good ______________ of electricity. These are primarily metals.
3)
The Intensity of current flow (I) is measured in ________________. This is a
measure of how many electrons are in motion at any specific point in a circuit.
4)
The electrical pressure pushing the electrons through a circuit is measured in
__________________. This is sometimes called Electromotive Force (EMF), because
that is a good description of what it is. The force that moves the electrons.
5)
The opposition to current flow is _________________, and is measured in Ohms.
6)
Electrical force moves down the wire at ______________________, 186,000
miles per second, or 300,000 kilometers per second, if you prefer.
7)
____________________ have a negative charge and flow from a negative voltage
toward a more positive voltage.
8)
Electricity that only flow in one direction through a circuit is called ___________.
9)
Electricity that flows first in one direction, then reverses, in cycles, is called
_________________________.
10)
How fast an AC current changes is called its __________________, and is
measured in Hertz (or Cycles per Second).
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1)
An atom is made of an inner nucleus of positively charged Protons and neutrally
charged Neutrons, with an outer shell of negatively charged Electrons. The protons and
neutrons are mostly matter and make up most of the mass of the atom.
2)
If the outer shell has only one or two electrons, the outer electrons may be pulled
away and move to a neighboring atom with relative ease. This is what makes an element
a good conductor of electricity. These are primarily metals.
3)
The Intensity of current flow (I) is measured in Amps (Amperes). This is a
measure of how many electrons are in motion at any specific point in a circuit.
4)
The electrical pressure pushing the electrons through a circuit is measured in
Volts. This is sometimes called Electromotive Force (EMF), because that is a good
description of what it is. The force that moves the electrons.
5)
The opposition to current flow is Resistance, and is measured in Ohms.
6)
Electrical force moves down the wire at the speed of light, 186,000 miles per
second, or 300,000 kilometers per second, if you prefer.
7)
Electrons have a negative charge and flow from a negative voltage toward a more
positive voltage.
8)
Electricity that only flows in one direction through a circuit is called Direct
Current.
9)
Electricity that flows first in one direction, then reverses, in cycles, is called
Alternating Current.
10)
How fast an AC current changes is called its Frequency, and is measured in Hertz
(or Cycles per Second).
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