Principles of Engineering
in Communications
Engineering Concepts
Communications
History of Communications
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1450 Johannes Gutenberg builds the movable printing press.
1826 Joseph Niepce of produces the wrold’s first permanent
photographic image.
1876-Alexander Graham Bell introduced telephone.
1877 Thomas Edison patents the phonograph.
1891 Thomas Edison and William Dickson invent the
kinetoscope.
1895 Guglielmo Marconi develops the wireless telegraph
1925 John Logie Baird transmits the first television signal.
1954 The transister radio or tubeless radios become available in
the USA
1990 The world wide web is created in Europe. It’s chief
architect is Tim Berners-Lee.
Communications
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Assignment 1:
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Have students pick one form of communication
technology and develop a PowerPoint presentation
to be presented to the class (See Communication Systems
PowerPoint Project)
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Assignment 2:
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Fill in the Principles of Engineering in Communications
vocabulary sheet as we go through this unit. Use the
PowerPoint, textbook, and any other resources to
complete the worksheet.
Communications
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Communication is the ability to send and
receive messages.
People to people
People to machine
Machine to people
Machine to machine
Communications
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Messages are intended to:
Inform – news papers, TV news casts
 Educate – texts, video, DVD’s, internet.
 Persuade - advertising
 Control – machines and tools such as Computer
Numeric Control: A type of programmable
control system, directed by mathematical data,
which uses microcomputers to carry out various
machining operations; such as a mill or lathe.
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Communications
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All Communications include a message, a
sender, a communication channel, and a receiver.
A communication channel is the path over
which a message must travel to get from the
sender to the receiver.
Communications
Communications
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The telegraph by Samuel Morse.
Sent electronic signals using wires.
Morse devised a language with a series of long
and short signals that represented letters and
numbers.
Video: Telegraph Machine
Communications
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Morse code
Assignment 3:
Using an old set of walkie
talkies, send a classmate a
message using Morse Code.
Communications
Video: Digital vs. Analog
Communications
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Electronics Components in
Communication
Transmission systems…
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Copper Wire: Many older phones consist
of two thin insulated copper wires twisted
around each other.
Coaxial Cable: Carry many more messages
all at once than twisted-pair wire. Consists
of an outer tube made of a material that
conducts electricity (usually copper). Inside
the tube is an insulated central conductor
(also copper). Several of these cables are
combined into one bundle.
Communications
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Optical Fibers: thin fibers
of pure glass that carry
signals in the form of
pulses of light. Each
optical fiber is surrounded
by a reflective cladding
and an outside protective
coating. The light pulses
are converted to electronic
signals.
Communications
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Microwaves can be used to carry phone conversations
over long distances. Microwaves are very short
electromagnetic waves that travel through the
atmosphere and make communication without
connecting wires possible.
In cell phones, sound waves are changed into
microwaves. They are transmitted using an antenna
(sent and received) and converted back to sound waves.
Communications
Circuits, Voltage & Current
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PARTS OF A CIRCUIT
An electric circuit is a combination of parts
connected from a complete path through
which electrons can move.
The purpose of a circuit is to make use of
energy of moving electrons.
Therefore a circuit is a system of parts, or
components by which electric energy can be
changed into other forms of energy.
Circuits, Voltage & Current
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HEAT, LIGHT & MAGNETISM
A basic complete circuit has four parts:
The energy source
 the conductors
 the load
 and the control device.
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Circuits, Voltage & Current
Light
Conductor
Wires
Energy
Source
Battery
Switch
Circuits, Voltage & Current
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ENERGY SOURCES
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Produces the force that causes electrons to move.
Similar to a pump that forces water through a pipe.
In electricity, this force is called voltage or
electromotive force.
Chemical Cells and electromagnetic generators.
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Circuits, Voltage & Current
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Because electrons are negatively charged, they
are attracted by positive charges and repelled
by negative charges.
If two charged objects are connected by a
conducting material such as wire, electrons
will flow from the negative object to the
positive object.
The flow of electrons is called current.
Circuits, Voltage & Current
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To produce a continuous electric current in the
wire, energy must be supplied continuously.
Electrons are not used up as they move through
a circuit.
Therefore the number of electrons that return to
the positive terminal of the power source equals
the number of electrons that leave the negative
terminal of that energy source.
Circuits, Voltage & Current
- + - ++ NEG. CHARGED
OBJECT
+++
+
+
- + POS. CHARGED
OBJECT
Circuits, Voltage & Current
-
-
+
+
+
+
+
+
- +++ NEG. CHARGED
OBJECT
FLOW OF
ELECTRONS
POS. CHARGED
OBJECT
Circuits, Voltage & Current
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CONDUCTORS
in a circuit, conductors provide an easy path
through which electrons can move through
the circuit.
Copper is the most commonly used
conductor metal.
Fashioned into wire or channels, copper wire
may be bare or covered with some kind of
insulating material.
Circuits, Voltage & Current
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The insulation wire provides a method to
prevent the conductors (wires) from touching
each other or some other conducting surface.
It prevents a short.
In some circuits, metal objects other than
copper conductors form the conducting
paths.
Circuits, Voltage & Current
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Laminated circuit boards or bread boards are
conductors.
Lets look at the bread board.
Circuits, Voltage & Current
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Breadboards are used for testing and
experimenting with electronic circuits.
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They are very convenient since all you have
to do is plug in the components.
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On the surface of a breadboard, there are
many holes for plugging in components:
Circuits, Voltage & Current
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The bread board has many strips of metal
which run underneath the board that
connects the component. The metal strips are
laid out as shown below:
Circuits, Voltage & Current
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Each strip is a connection. So whichever
components connected to a certain strip are
connected to each other.
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The blue strips shown in the illustration are
usually used for connecting the batteries and
the green strips are for the components.
Circuits, Voltage & Current
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LOAD
The part of the circuit that changes the energy
of moving electrons into some other useful
form of energy.
A light bulb is a very common circuit load.
As electrons move through the filament of the
lamp, the energy of the electrons in motion is
changed into heat energy and light energy.
Circuits, Voltage & Current
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Loads can be connected into a circuit in
series and parallel or in series-parallel
combinations.
A series circuit provides only one path or one
loop through which electrons can move from
one terminal of the energy source to the
other.
Circuits, Voltage & Current
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In a parallel circuit there may be two or more
different paths, or loops.
A series-parallel circuit has a combination of
both parallel and series circuits in a single
circuit.
Circuits, Voltage & Current
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CONTROL DEVICE:
The mechanical wall switch is an example of
a simple circuit control.
When the switch is in the on position, it acts
as a conductor to keep electrons flowing
continuously through the circuit.
The circuit is said to be CLOSED or a closed
loop.
Circuits, Voltage & Current
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When the switch is in the off position, the
circuit path is interrupted.
Electrons can no longer move through the
circuit.
The circuit is said to be OPEN or an open
loop.
Different types of control devices.
Circuits, Voltage & Current
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VOLTAGE:
As stated earlier, the energy that forces electrons
through a circuit is called the electromotive
force.
The EMF is measured in units called volts.
It is referred to voltage.
Most homes operate on 120.
A common flashlight battery produces 1.5 volts
Circuits, Voltage & Current
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CURRENT:
The movement of electrons is called current.
It is measured in amperes or amps.
One ampere of current is equal to one
coulomb (6,240 quadrillion) of electrons
passing past any point in a circuit during one
second of time.
Circuits, Voltage & Current
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A 100 watt light bulb requires about .8 amps of
current to operate.
Most starters in cars use 200 amps when it is
switched on.
VOLTAGE AND CURRENT REQUIREMENTS:
Sources od energy must be able to do two things.
Supply the voltage
Deliver the current as required by the device.
Circuits, Voltage & Current
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You can connect 8 flashlight dry cells
together in such a way as to form a battery
that produces 12 volts.
However you would never get the car to start
with this energy source.
In order to do that a larger battery also
producing 12 volts but having a much larger
current-delivering capacity must be used.
Circuits, Voltage & Current
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It is important to know both the voltage and
current requirements are often given on the
name plates attached to these products.
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DIRECT CURRENT (dc)
Is produced in a circuit by a steady voltage
source.
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Circuits, Voltage & Current
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That is, the positive and negative terminals, or
poles, of the voltage source do not change
their charges over time.
These terminals are said to have fixed
polarity.
Therefore the direction of the current does
not change over time.
Such a voltage is provided by electric cells,
batteries and dc generators.
Circuits, Voltage & Current
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DC may be constant, or steady, in value.
The current also may be varying or pulsating.
The applied voltage and the nature of the
load determine the kind of direct current
supplied.
Circuits, Voltage & Current
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ALTERNATING CURRENT (ac)
produced by a voltage source that changes
polarity, or alternates, with time.
The current moves in one direction and then
another direction over time.
The most common source is a an alternating
current generator or alternator.
Circuits, Voltage & Current
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For purposes of our project we will be using
DC power.
Circuits, Voltage & Current
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RESISTANCE
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To better understand what resistance is, you
must first get an idea of how electrons flow.
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When an electron is knocked out of an atom, it
will fly off and hit another atom. If the electron
strikes the atom with enough force, it will knock
off another electron. The atom that was just
knocked off will hit another atom and so forth.
Circuits, Voltage & Current
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Note that every time an electron strikes
another, it is transferring its energy. Some of
the energy is converted into heat every time it
is transferred.
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The voltage will drop as the energy is
transferred over long distances.
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Thus a long wire has a higher resistance than
a short wire.
Circuits, Voltage & Current
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Some materials - such as copper and silver does not hold on to its electrons very tightly.
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Therefore it doesn't require much energy to
knock off an electron.
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These materials are called conductors and has
a very low resistance to electron flow.
Circuits, Voltage & Current
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Materials such as clay and plastics hold on to their
electrons more tightly than conductors. It takes
more energy to knock off an electron from these
materials. These materials are called insulators and
has a high resistance to electron flow.
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Now, you must understand that this is NOT how
electrons really flow; It serves only as something for
you to work with. To really know how electrons
flow, which we will not get into, you will need to
study quantum physics
Circuits, Voltage & Current
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Resistance is represented by the letter R.
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The basic unit of measure is ohm or the
symbol (Greek omega).
Circuits, Voltage & Current
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OHM’S LAW
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Ohm's law is one of the most important concepts in
electronics. Fortunately it's only a very simple mathematical
relationship between current, voltage, and resistance.
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According to the Ohm's law, voltage equals current times
resistance which is expressed in the following equation:
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E=IR
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where E = voltage, I = current, and R = resistance
Circuits, Voltage & Current
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For example, if
I = 0.1A
R = 10k
then
E = 0.1 * 10k
E = 1000 volts
See excel spreadsheet: Ohms Law
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Note: "k" stands for "thousands". So 10k = 10,000 ohm
Circuits, Voltage & Current
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COMPONENTS
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Resistors are one of the most commonly
used components in electronics.
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As its name implies, resistors resist the flow
of electrons.
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They are used to add resistance to a circuit.
Circuits, Voltage & Current
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The color bands around the resistors are
color codes that tell you its resistance value.
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Recall that resistance is measured in ohms.
Circuits, Voltage & Current
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The tolerance bands
indicates the accuracy of
the values. A 5% tolerance
(gold band) for example,
indicates that the resistor
will be within 5% of its
value. For most
applications, a resistor
within 5% tolerance
should be sufficient.
Circuits, Voltage & Current
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To get the value of a resistor, hold
the resistor so that the tolerance
band is on the right.
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The first two color bands from the
left are the significant figures simply write down the numbers
represented by the colors. The third
band is the multiplier - it tells you
how many zeros to put after the
significant figures. Put them all
together and you have the value.
Circuits, Voltage & Current
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One last important note about resistors is
their wattage rating. You should not use a 1/4
watt resistor in a circuit that has more than
1/4 watt of power flowing.
For example, it is NOT okay to use a 1/4
watt resistor in a 1/2 watt circuit. However, it
is okay to use a 1/2 watt resistor in a 1/4 watt
circuit.
Circuits, Voltage & Current
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CAPACITORS
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Capacitors are the second most commonly
used component in electronics.
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They can be thought of as tiny rechargeable
batteries.
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Capacitors can be charged and discharged.
Circuits, Voltage & Current
•Ceramic capacitors are brown and has a disc shape. These capacitors
are non-polarized, meaning that you can connect them in any way. To
find the value, you simply decode the 3 digit number on the surface of
the capacitor. The coding is just like the resistor color codes except that
they used numbers instead of colors. The first 2 digit are the significant
figures and the third digit is the multiplier. These capacitors are
measured in pF.
Circuits, Voltage & Current
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Electrolytic Capacitors has a cylinder shape. These capacitors are
polarized so you must connect the negative side in the right
place. The value of the resistor as well as the negative side is
clearly printed on the capacitor. These capacitors are measured in
µF.
Circuits, Voltage & Current
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DIODES
Diodes let electrons flow through them only
in one direction. Diodes flow from cathode
to anode. The cathode side of the diode is
marked with a band around it
Circuits, Voltage & Current
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Light Emitting Diodes (LED for short) are just like the
regular diodes except that it lights up when electrons
are flowing through. Note: there aren't any bands to
identify which pin is anode and which is cathode.
However, one pin is longer then the other. The longer
pin is the anode, the positive side.
Circuits, Voltage & Current
PNP
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TRANSISTORS
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Transistors are used as switches and
amplifiers. We will discuss two types of
transistors: PNP and NPN transistors. Both
of these transistors has 3 pins: emitter, base,
collector.
NPN
Circuits, Voltage & Current
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To allow electrons to flow through the
collector and emitter of a PNP transistor,
the following must apply:
The emitter is more positive than the base
and the collector leads to the negative
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The NPN transistor is the opposite:
The collector must be more positive than the
base and the emitter leads to the negative.
Circuits, Voltage & Current
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INTEGRATED CIRCUITS (chips)
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Logic circuits These IC's are basically decision makers. most contain logic gate circuits.
(logic gates will be discussed in a later section).
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Comparators These IC's compare inputs and gives an output.
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Operational Amplifiers These are amplifiers. Works very much like transistor amplifier circuits.
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Audio amplifiers These are used to amplify audio.
Circuits, Voltage & Current
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Timers These are counting IC's used for circuits that counts or needs to keep
track of time.
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Switches Switching IC's are also very much like the switching circuits of transistors
Circuits, Voltage & Current
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SPST = Single Pole, Single Throw
This is a two terminal switch that opens and closes a
circuit.
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SPDT = Single Pole, Double Throw
This is a three terminal switch that connects one
terminal to either of the other two.
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DPDT = Double Pole, Double Throw
This is a six terminal switch that connects a pair of
terminals to either of the other two pairs.
Circuits, Voltage & Current
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SCHEMATIC DIAGRAM
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A schematic diagram shows how each
component connect with another.
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It is a simple and easy to read outline of the
circuit.
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Each type of component has a unique
symbol and a name(usually 1-2 letters).
Circuits, Voltage & Current
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All relevant values and component specific
information are usually included.
Below is an example of a schematic diagram:
Circuits, Voltage & Current
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The 4 horizontal lines is the battery. The
triangle in the circle represents the light
emitting diode and the wavy lines represent
the resistor -- both of which will be discussed
in the components section.
Circuits, Voltage & Current
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Lets Build this one together!
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battery
led
R1
Circuits, Voltage & Current
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SAMPLE CIRCUITS
Circuits, Voltage & Current
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Use Mr. Circuit One and have students complete all lessons.
Use Mr. Circuit Three and have students complete lessons:
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2 – RESISTORS
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3 - OHM’S LAW
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4 – SERIES CIRCUITS AND THE VOLTAGE DIVIDER RULE
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5 – KIRCHOFF’S VOLTAGE LAW
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6 – PARALLEL CIRCUITS AND THE CURRENT DIVIDER
RULE
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8 – SERIES PARALLEL ANALYSIS
Circuits, Voltage & Current
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Video: Cyborg Technologies
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CYBORG MASKS (see Cyborg Mask Project.doc)
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We won’t be quite that complex. We will create
an electronic device that will depend upon simple
parallel circuits and a developed code to
communicate.