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Mr. McClean
Concepts of Engineering
Electrons are the negatively charged particles of an atom. Together, all of the
electrons of an atom create a negative charge that balances the positive charge
of the protons in the atomic nucleus. Electrons are extremely small compared
to all of the other parts of the atom. The mass of an electron is almost 1,000
times smaller than the mass of a proton. It can be either free (not attached to
any atom), or bound to the nucleus of an atom. Electrons in atoms exist in
spherical shells, representing energy levels. The larger the spherical shell, the
higher the energy in the electron.
ELECTRONS
The valence electrons are the electrons in the outer shell of an atom.
They are the ones involved in forming bonds to adjacent atoms.
Therefore, the number of valence electrons is important for
determining the number of bonds an atom will form. The valence
electrons are the electrons on an atom that can be gained or lost in a
chemical reaction.
VALENCE ELECTRONS
Protons are positively charged particles found within an atom. A
proton is a tiny particle, smaller than an atom. Protons are too small
to see, even with an electron microscope, but we know they must be
there because that's the only way we can explain how atoms behave.
To give you an idea how small a proton is, if an atom was the size of
a football stadium, then a proton would still be smaller than a marble.
PROTONS
An atom is the smallest unit of matter that defines the chemical elements.
Every solid, liquid, gas, and plasma is made up of atoms. Atoms are very
small. Atoms are building blocks. If you want to create a language, you'll
need an alphabet. If you want to build molecules, you will need atoms of
different elements. Elements are the alphabet in the language of molecules.
Each element is a little bit different from the rest. Atoms are the general
term used to describe pieces of matter. You have billions of billions of atoms
in your body. However, you may only find about 40 elements.
ATOMS
A covalent bond is a chemical bond
that involves the sharing of
electron pairs between atoms.
The stable balance of attractive
and repulsive forces between
atoms when they share electrons
is known as covalent bonding.
COVALENT BOND
Voltage, also called electromotive force, is an expression of the potential
difference in charge between two points in an electrical field. The greater
the voltage, the greater the flow of electrical current. We define voltage as
the amount of potential energy between two points on a circuit. One point
has more charge than another. This difference in charge between the two
points is called voltage.
VOLTAGE
The degree to which a
specified material
conducts electricity. A
conductor is an object
or material that allows
the flow of electricity,
like a wire or piece of
metal.
CONDUCTIVITY
An electrical insulator is a material
whose internal electric charges do not
flow freely, which makes it hard to
conduct an electric current under the
influence of electricity. An example is
a rubber cord. A perfect insulator does
not exist, because a portion of the
insulator could become electrically
conductive if the voltage applied
across it exceeds the breakdown
voltage.
INSULATION
In electronics, a circuit is a path between two or more points along
which an electrical current can be carried. A circuit breaker is a
device that interrupts the path when necessary to protect other
devices attached to the circuit - for example, in case of a power
surge.
CIRCUIT
A transistor is a semiconductor device used to amplify and switch
electronic signals and electrical power. It is composed of
semiconductor material with at least three terminals for connection
to an external circuit. A voltage or current applied to one pair of the
transistor's terminals changes the current through another pair of
terminals. Because the controlled (output) power can be higher than
the controlling (input) power, a transistor can amplify a signal.
TRANSISTOR
A power inverter is an electronic device or circuitry that changes
direct current (DC) to alternating current (AC). An example
would be a solar plant.
INVERTER
A resistor is a passive two-terminal electrical component that implements
electrical resistance. Resistors act to reduce current flow and act to lower
voltage levels within circuits. In electronic circuits resistors are used to
limit current flow, to adjust signal levels, terminate transmission lines
among other uses.
RESISTOR
An inductor, also called a coil, is a passive two-terminal electrical
component which resists changes in electric currents passing. It consists
of a conductor such as a wire, usually wound into a coil. When a current
flows through it, energy is stored temporarily in a magnetic field in the
coil.
INDUCTOR
A capacitor is a passive two-terminal electrical component used to store
energy electrostatically in an electric field. All capacitors contain at least
two electrical conductors (plates) separated by an insulating substance.
CAPACITOR
In electronics, a diode is a two-terminal electronic component
with asymmetric conductance; it has low (ideally zero) resistance
to current in one direction, and high (ideally infinite) resistance
in the other.
DIODE
An electrical device that can interrupt the flow of electrical current
when it is overloaded. A fuse interrupts excessive current ("blows") so
that further damage by overheating or fire is prevented.
FUSE
A semiconductor is a substance that can conduct (allow) electricity under
certain conditions but not others, making it a good medium for the control of
electrical current. It is a solid substance that has a conductivity between that
of an insulator and that of most metals, either due to the addition of an
impurity or because of temperature effects. Devices made of semiconductors,
notably silicon, are essential components of most electronic circuits.
SEMICONDUCTOR
A binary code represents text or computer processor instructions using
the digits 0 and 1. A binary code assigns a bit string to each symbol
or instruction. For example, a binary string of eight binary digits
(bits) can represent any of 256 possible values and can therefore
correspond to a variety of different symbols, letters or instructions.
The number one represents the ON state or condition of a device. The
number zero represents the OFF state or condition of a device.
Combine billions of devices into one machine and you can wire
them to do arithmetic calculations and sorting operations.
BINARY CODE
Analog and digital signals are used to
transmit information, usually through
electric signals. In both these
technologies, the information, such
as any audio or video, is transformed
into electric signals. The difference
between analog and digital
technologies is that in analog
technology, information is translated
into electric pulses of varying
amplitude. In digital technology,
translation of information is into
binary format (0 or 1).
ANALOG AND DIGITAL
SIGNALS
Batteries, fuel cells and solar cells all produce something called Direct Current (DC). The
(+) and (-) terminals of a battery are always positive and negative. Current always flows in
the same direction between those two terminals.
The power that comes from a power plant, on the other hand, is called Alternating Current
(AC). The direction of the current reverses, or alternates. The power in a wall socket in the
US is 120-volt of AC power. AC also has some useful properties, such as being able to
convert voltage levels with a single device (a transformer), which is why AC was chosen as
the primary means to transmit electricity over long distances. AC can be produced using a
device called an alternator.
Direct Current:
Tank of Water
ALTERNATING CURRENT
DIRECT CURRENT
A ground fault circuit interrupter (GFCI)
is a device that shuts off an electric circuit
when it detects that current is flowing
along an unintended path, possibly
through water or through a person. It is
used to reduce the risk of electric shock.
It works by measuring the current leaving
the hot side of the power source and
comparing it to the current returning to
the neutral side. If they are not equal, this
means that some of the current is flowing
along an unintended path, and the GFCI
shuts the power off.
GFCI
When creating semiconductors, doping intentionally brings impurities into an extremely
pure (Intrinsic) semiconductor for the purpose of changing its electrical properties. The
impurities depend on the type of semiconductor. Lightly doped semiconductors are called
Extrinsic. A semiconductor doped to such high levels that it acts more like a conductor
than a semiconductor is referred to as Degenerate.
Again, doping is the process of adding impurities to intrinsic semiconductors to alter their
properties.
N AND P DOPING
End