Electrical Principles
 There are two main types of energy: kinetic and potential.
 Kinetic energy is energy of motion.
 Any object or particle that is moving has kinetic energy.
 http://www.youtube.com/watch?v=2MkAZu6QW0I
 Potential energy is stored energy.
 Any object or particle that has energy but is not using it has
potential energy.
 http://www.youtube.com/watch?v=pNl8flwGWD8
 The unit of energy is the Joule (J).
http://www.youtube.com/watch?v=8ab
zpXCjyjA&feature=PlayList&p=8F4E5
BB40872CB7E&index=0&playnext=1
Other Types of Energy
 mechanical energy- the combined total of kinetic and
potential energies
 chemical energy- a type of potential energy; the
energy stored in the bonds of molecules
 thermal energy- a type of kinetic energy; the energy
of vibrating particles in a material
 electrical energy- a type of potential energy; the
energy carried by charged particles
Energy Transfer
 An electric motor is used to turn something. It converts
electrical energy to mechanical energy.
 A generator produces electricity. It converts mechanical
energy to electrical energy.
 A thermocouple produces electricity. It converts
thermal energy to electrical energy.
 A cell/battery produces electricity. It converts chemical
energy to electrical energy.
http://www.youtube.com/watch?v=E69RSok2TQ
Electrical Storage Design
 Electrochemical cell: a package of chemicals designed to
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produce small amounts of electricity e.g. a battery.
Dry cell- converts chemical energy to electrical energy.
Two electrodes (two different pieces of metal) and an
electrolyte (a conducting solution).
Charges leave the negative electrode, pass through the
electrolyte, and return to the positive electrode.
Called dry cells because the electrolyte is like a paste.
Wet cell- Same as above, but the electrolyte is a liquid that
is usually an acid.
Salt bridge allows the
exchange of ions.
http://www.youtube.com/watch?v=HlGITf-rhCE
http://www.youtube.com/
watch?v=0oSqPDD2rMA
 Dry cells and wet cells are both examples of primary cells.
The reaction cannot be reversed, and as a result, the cells can
only be used once.
 Rechargeable cells are known as secondary cells. Two
examples of rechargeable cells are Ni-Cd and Nickel metalhydride.
Electric motors
 2 types: AC and DC
 Motors need energy to make a coil of wire spin between a
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magnet
Armature: rotating coil of wire
Electromagnet: a coil of wire wrapped around a magnet
Commutator: a metal “switch” with split rings
An electromagnet will move to line up with the magnetic
field of a nearby permanent magnet
To keep the electromagnet spinning, motors use a
commutator (split ring) and brushes.
http://www.youtube.com/watch?v=it_Z7NdKgmY
 http://www.youtube.com/watch?v=Xi7o8cMPI0E
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 DC Motor
 Electrons flow from the battery to the commutator and then
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armature, North is repelled by North and attracted to South
The armature begins to rotate
As the armature passes the field magnets, current is cut off,
the armature continues to spin because of momentum.
The commutator then reconnects!
The commutator reverses the current in the armature and
the polarity of the magnets
MP3s, cell phones, computers, calculators
Electric DC Motor
A)
-Electrons flow to the right from
the battery to the commutator
into the armature.
-North pole of armature is
repelled by the top of the field
magnet and attracted by the
bottom of the field magnet.
- Armature begins to rotate
clockwise.
B)
-The commutator cuts off the
current so the armature does not
stall.
- Armature keeps spinning due to
momentum.
C)
-The commutator reverses the
direction of current through the
armature and polarity of magnets.
- This allows armature to keep
spinning.
 AC Motor
 Found in dishwashers, washing machines, garage door
openers, furnaces
 Rotating core or rotor
 Stationary component or stator
 The motor functions based on magnetic attraction and
repulsion.
AC Electric Motor
-Operate on alternating current.
- They have a rotating core, or rotor
that is held in a laminated steel
cylinder.
- Surrounding the rotor is a
stationary component called a
stator.
- Stator is a two pole (north and
south) electromagnet.
- When the AC motor is turned on,
the attraction and repulsion causes
the rotor to spin.
Electric Generator
 Electric current is produced when a coil of wire rotates
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inside a magnet
AC generator
Coil of wire rotates inside a stationary field magnet
The coil rotates due to an external force ex. falling water
As the wire rotates, electrons move in 1 direction, after half a
turn, it passes the opposite magnetic pole
This makes the electrons (and the wire) rotate in the
opposite direction
Car electrical systems
http://www.youtube.com/watch?v=d_aTC0iKO68
Electrical Generator
AC Generator (Alternating Current)because current changes direction.
-Coil of wire rotates inside a stationary
field magnet.
-The coil rotates due to an external
force ex. falling water, steam, wind.
- Electric current is produced when a
coil of wire is rotated inside a magnet.
- As the wire rotates, electrons move
in 1 direction, after half a turn, it
passes near the opposite magnetic
pole. This makes the electrons rotate
in the opposite direction
 DC generator (dynamo)
 Armature connected to split ring commutator
 Current flows when the brushes touch the metal rings
 At the gaps current flow (electron flow) stops
 Then the direction and the flow of charge have reversed
DC Generators
 There are several ways to change the speed at which the
armature in a motor spins:
 increasing the strength of the magnets increases the speed of the
armature
 increasing the current increases the speed of the armature
 increasing the number of coils of wire between the magnets
increases the speed of the armature
 changing the orientation of the magnets so that like poles are
against each other will stop the armature
Danger of Electrical Devices
 The voltage is the energy of individual charges.
 Total energy provides the danger, so a high voltage does not
present a significant danger if there are not a lot of charges
(low current).
 It becomes dangerous when the current (number of charges
per second) is also increased to a high level, providing more
overall energy.
 To assess the danger of an electrical device, check the
manufacturer’s label for voltage and current rating.
 Remember that it is the combination of high voltage and high
current that provides the danger.
 http://www.youtube.com/watch?v=IEa04gZbWRU
Safety
 Never handle electrical devices when you are wet or
near water unless they are specially designed and
approved for use in wet areas.
 Don’t use any power cord that is frayed or broken.
 Always unplug electrical devices before looking inside or
servicing them.
 Don’t put anything into an electrical outlet other than
proper plugs for electrical devices.
 Don’t overload circuits by plugging in
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and operating too many devices.
Stay away from power lines.
Don’t bypass safety features built into
home wiring, appliances, and other
electrical devices.
When unplugging a device, pull on the
plug, not on the electrical cord.
Never remove the third prong from a
three-prong plug.
Static and Current
 Static electricity- the build-up of electric charges
(protons and electrons are not equal!). Electrons flow
from one object to another, making one positive charge
and the other negative overall (due to rubbing or
touching).
 Charged objects cause charge separation when they
are brought close to neutral objects.
 e.g. the build-up of charges in your hair when you put a
wool sweater on; these charges are transferred from the
wool to your hair
 e.g. lightening results from a build-up of charges in
clouds; when the build-up becomes to large, the charges
jump (discharge) to the ground
Electric Discharge
 When something has a build up of electric charges, getting
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rid of that charge is “discharging it.”
For example, two metal plates near each other, but not
touching will build up equal and opposite amounts of charge
when connected to a battery.
When the battery is disconnected the plate charges will
remain.
The charges will move from one plate to the other so the
number of positive and negative charges on each plate is
equal and resulting in no net charge build up.
Sometimes the charge buildup is large enough that it will
discharge thru the air and you see it as a spark.
http://www.youtube.com/wa
tch?v=YFeFsw3Ht2c
 Current electricity- the flow of electric charges; the
more charges that flow per second, the higher the
current.
 In general, electrical current carries electrical potential
energy which is used to operate electrical devices
 e.g. Charges with electrical energy flow through a light
bulb; the electrical energy from the charges is converted
to light and heat
Conductors and Insulators
 Electrical conductor- a material that allows charges
to flow through it; some materials are better conductors
than others in that they allow charges to flow easier
 e.g. Most metals are good conductors; copper is a very
good conductor and is used to carry charges through
your house, while nichrome wire conducts charges but
not as well.
 Superconductor – almost no resistance to electron flow,
used in power lines and super computers.
 Some materials become Superconductors in low
temperatures.
 eg. Mercury at absolute zero.
 Electrical insulator- a
material that does not allow
charges to flow through it;
insulators offer resistance to
the flow of electric charge.
 If something is a good
insulator, it is a poor
conductor.
 e.g. rubber, plastic, cotton,
glass, pure water
 Resistance- something that hinders the motion of
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electric charge and converts electric energy into other
forms of energy such as light, heat, and sound.
Symbol is R and units are Ohms ().
e.g. filament in a light bulb generates heat due to
resistance
e.g. lie detectors – measures skin resistance because
sweat is a salty and conductive solution
As wire length increases, resistance increases
As temperature increases, resistance increases
As area decreases, resistance decreases
Resistance cont.
 Resistance is the friction in an electrical circuit that controls
the flow of current.
 Voltage is the pressure pushing on the electrons in a circuit.
 Why do we need resistance?
- Not enough resistance?
- Too much resistance?
- Exactly enough resistance?
Not enough Resistance
 IF we use a 6 Volt battery and a bulb that is intended for 1 ½
Volts, the pressure is too high and the filament resistance
allows too much current to flow. We get a single bright flash
as the bulb burns out!
Too much Resistance
 If we use a 1 ½ Volt battery and a bulb that is intended for 6
Volts, the pressure is too low and the filament resistance
allows very little current to flow. The battery lasts for a very
long time but the bulb is too dim to be of much use.
Exactly Enough Resistance
 When we use a 1 ½ Volt battery and a bulb that is also
intended for 1 ½ Volts, the current is just right. The bulb is
bright, but it doesn’t burn out, and the battery lasts for quite
a while.
Electrical Flow
 Switch- something that will start or stop electric current
 Resistor- something that resists the flow of electric charge, takes
electrical potential energy from charges and converts it to some
other type of energy (light, heat, sound, etc)
 Rheostat- a resistor whose resistance value can be changed
 Nichrome wire has a high resistance, adding more nichrome wire
to a circuit will increase the overall resistance.
 Taking nichrome away will decrease the overall resistance.
Voltage
 Potential difference: the difference
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in energy per unit of charge
between one point in the circuit
and another point.
The energy of an individual charge.
The symbol for voltage is the letter
V and the units are Volts (V).
Volts are measured with a voltmeter.
Pretend an electric circuit is a race
track. Each car represents a
charge. Each car has a certain
amount of gasoline that provides its
energy.
 The gasoline that each car has would represent the voltage.
 The number of cars that pass by the starting line every second
would represent the current.
 As cars (charges) go up hills (resistors), each one uses up
gasoline (voltage).
 Each car needs to get more
gasoline (voltage) at the pit
stop (battery).
Current
 Amperage- a measure of the
strength of electric current.
 The symbol for amperage is the
letter I and the units are Amps
(A).
 Amperage is measured with an
ammeter.
 Smaller currents are measured
with galvanometers.
 Ohm’s law shows the
relationship between voltage
across a resistor (the energy
that each charge loses across
the resistor), the current
through the resistor (the
amount of charges that are
flowing through the resistor
each second), and the
resistance of the resistor.
Resistance: Ohms Law
 Shows the relationship between voltage, current and
resistance.
Given a fixed resistance, more voltage causes more
current.
2. Given a fixed voltage, more resistance causes less current.
1.
 Ohm’s law can be written as a mathematical equation:
 e.g. An electric dryer draws an electric current of 22 A. The
voltage drawn by the dryer is 220 V. What is the resistance of
the dryer?
 Given: I=22 A V=220 V
 Find: R = ?
V 220V
R 
 10
I
22 A
TRY THESE !
 Suppose that our bulb has a resistance of 50 ohms and we
know that is should be used with a current of 0.03 amps.
What battery voltage is needed?
 Now supposed that we have a 3 Volt battery and that our
bulb has a resistance of 100 ohms. How much current is
flowing when the bulb is lit?
 Now suppose that we have a 4.5 V battery and that there is
0.03 Amps of current flowing. What is the bulb resistance?
 1.5 V, 0.03 amps, 150 ohms.
Photoelectric Cell
 A photoelectric cell uses light to emit electrons. These
electrons can go around an electric circuit and power
devices.
 The burglar alarm uses a beam of UV light to cause
electrons to be emitted from the photoelectric cell,
causing the iron to become magnetized.
 This magnetized iron attracts the switch from the second
circuit, breaking that circuit, preventing the alarm from
sounding.
 When the burglar breaks the
beam of UV light, no electrons
flow in the first circuit so the
iron loses its magnetism. The
switch from the second circuit
falls closed, completing the
second circuit, causing the
alarm to sound.
 An electrical circuit is a system made up of 4 subsystems:
1. Source – cell or battery
2. Conductor – wire
3. Control – switch
4. Load – lamp/motor
http://www.youtube.com/watc
h?v=E8AZBR8Zz04
The following is a list of symbols used
when drawing electric circuit diagrams.
Series Circuit
 A series circuit is when the current passes through each load
in the circuit. In a series circuit there is only one path for
the current to pass through.
 A parallel circuit has more than one path, so current does not
necessarily pass through each load. In this case, it one path is
broken there is still at least one other path for current to
come through.
Summary
 Series circuits are basic types of electrical circuits in which all
components are joined in a sequence so that the same current
flows through all of them.
 Parallel circuits are types of circuits in which the identical
voltage occurs in all components, with the current dividing
among the components based on their resistances, or the
impedances.
 In series circuits, the connection or circuit will not be
complete if one component in the series burns out.
 Parallel circuits will still continue to operate, at least with
other components, if one parallel-connected component
burns out.
Microelectronic Circuits
 The similarity between household circuits and
microelectronic circuits is that they perform the same basic
function: to power an electrical device.
 The primary difference between household circuits and
microelectronic circuits is the scale.
 Household circuits are on a much bigger scale. In a typical
house, you might have dozens of electrical components.
 On a typical microelectronic (integrated circuit), there may
be millions of transistors(acts as a switch) and resistors.
Microcircuit a circuit on a small scale.
Forms of Energy Inputs and Outputs
 e.g. lightbulb- the input energy is electrical, the output
energy is light and heat.
 e.g. cd player- the input energy is electrical, the output
energy is sound (and also kinetic as the disc spins)
Energy Transformations
 Power- the rate at which a device converts energy.
 The symbol is P and the units are Watts (W).
 1 Watt is equal to 1.0 J/s.
 There are two equations that describe power relationships:
 P = IV and E = Pt
 e.g. A 100 W light bulb is plugged into a 120 V outlet and is on for
5 minutes.
 What is the current?
 Given:
P=100 W
V=120 V
t=5 minutes = 300 seconds
P 100W
P  IV  I  
 0.83 A
V 120V
 What is the energy used?
E  Pt  (100W )(300s)  30000J
 The law of conservation of energy states that
energy cannot be created or destroyed, but that it can be
transformed from one type to another.
 Efficiency refers to the percentage of original energy
(input) that remains after an energy conversion (output).
 No device is 100% efficient. This does not mean that
energy is destroyed; it was simply converted to an
another unusable form such as heat.
 e.g. A light bulb uses electrical energy input to produce light.
 The conversion is not 100% efficient. Some of the energy is
lost in the form of heat.
 Note that no energy was destroyed!!
 Efficiency Equation
useful_ energy_ output
%Efficiency
x100%
total _ energy_ input
 e.g. A light bulb uses 780 J of electric energy, but produces only
31 J of light energy. What is the efficiency of the light bulb?
 Given:
Useful energy output=31 J
Total energy input=780 J
 Find: % Efficiency
% Efficiency 
useful _ energy_ output
31J
x100% 
x100%  3.9%
total _ energy_ input
780J
Reducing Energy Waste
 pick appliances that are energy
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efficient (they have energy labels
on them)
don’t leave lights on when not in
the room
do full loads of laundry and dishes
improve bearings and lubricants in
devices to reduce friction
add more insulation around stoves,
refrigerators, and walls
Energy Sources
 Renewable source- a source of energy that can
replenished naturally in a relatively short period of time
 Tides- moving water from tides turn turbines that run
generators.
 There are not a lot of tidal power stations in the world
because of the difficulty in finding a suitable location.
 Environmentally friendly source of energy.
 Dams: Hydro-electric plants like those near Niagara
Falls, capture the energy of falling water. When water
falls over the damn, it drives a generator, producing
energy.
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http://www.youtube.com/watch?v=1cysaOnlv_E
http://www.youtube.com/watch?v=F3TUTfy1n60
 Wind- use the wind to turn a turbine and
run a generator
 Modern windmills are more efficient than
older ones because of the propeller shaped
blades.
 Not particularly efficient, but are
environmentally friendly.
 Usually grouped together in wind farms,
such those in Pincher Creek.
 Sunlight- uses the Sun to generate electricity
 Modern technologies have made sunlight a more
efficient way of producing current.
 Solar cells are now used in many applications, including
calculators and spacecraft and the International Space
Station.
 Environmentally friendly.
 Solar technologies can be either passive or active
depending on the way they capture, convert and
distribute sunlight.
 Active solar techniques use photovoltaic panels, pumps, and fans
to convert sunlight into useful outputs.
 Passive solar techniques include selecting materials with
favorable thermal properties, designing spaces that naturally
circulate air, and referencing the position of a building to the
Sun.
 Batteries – Convenient source of electricity for portable
devices, but they only produce energy after being charged
using electricity from an external source.
 They actually use more energy than they produce!
 Non-renewable source- energy that cannot be
replenished naturally in a relatively short period of time.
 Such as fossil fuels: coal, oil, and natural gas.
 Fossil fuels are a reasonable choice in areas that have
large deposits that are easy to excavate.
 Mining coal or tapping into deposits of oil and natural
gas is only the first step in refining fossil fuels in order to
generate electricity from fossil fuels.
 Not environmentally friendly.
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http://www.youtube.com/watch?v=vBbhfQ1kDfw
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http://www.youtube.com/watch?v=fjgdgAhOzXQ
Air Pollution from Fossil Fuels
 Fly ash : When coal is burned fly ash is released into the
air. Fly ash contains mercury, a poisonous metal that can
damage the nervous system.
 sulphur dioxide: has been identified as causing acid rain
 nitrogen oxides: major cause of air pollution and acid
rain
 carbon dioxide: has been identified as causing global
warning
 Strip-mining
 Used when deposits are near
the surface.
 Coal is often mined using this
method, and the coal can be
used to generate electricity.
 This type of mining removes
all plants and animals from
the area. The natural
environment is never fully
restored.
 Oil and gas fired generators
 Oil or gas is burned to heat water,
which becomes steam and turns a
turbine to generate electricity.
 This process releases poisonous
gases and warm water into nearby
lakes and rivers.
 There is a need to monitor plants
and animals in the area to ensure
their health.
 Oil is pumped from wells, sometimes by injecting water into
the ground. A significant amount of fresh water goes into the
ground, out of the water cycle forever. Natural gas wells
produce sour gas which is poisonous.
Technologies Based on Electricity
 Computers
 may make tasks more time efficient, more instant
communication
 lots of waste produced when computers are discarded
 Cell Phones
 Instant communication of words and pictures
 People are always reachable
 Lasers
 used in cd players, medical applications such as surgeries, dental
work, communication
 the cost can be downside, although the cost is decreasing
 In general, many people would argue that technology
had made our lives easier. Some would argue, however,
that we are experiencing an information overload and
are working harder than ever as a result of technology.
Electrical Technology Issues
 Concerns
 shrinking natural resource reserves
 increasing demand on natural resources
 environmental concerns with the means in which resources are
obtained, used, and discarded
 Some ways to improve the sustainability of energy use:
 manage resources according to what we have rather than what
we use
 improve the efficiency of machines and appliances
 use more renewable sources of energy, and avoid the use of
non-renewable energy sources
 make good personal choices