Unit d electrical principals & technologies notes

1. Unit D: Electrical Principals
& Technologies

2. Static Electricity

3. Balloon Demo
 Rub your balloon on your shirt
 What happens when you hold it over confetti?
 Why did this happen?
 What happens if you put 2 balloons next to each other facing
the same way? What about facing the opposite way?
 Why did this happen?
 Try sticking it to the wall and sticking it to metal

5. Static Electricity
 Static: Not moving
 Electricity: Electrons that are moving or
could move
 Static Electricity: is a build up of electrons
on an area or surface that are not moving
or flowing.

6. Electrical Charge
 As we have learnt, elements are
made of protons neutrons and
electrons.
 Protons are positive
 Electrons are negative.
 Objects may become charged or are
neutral having no charge
 Like charges repel each other
 Opposites attract

7. Electrical Discharge
 An electrical charge can build up.
 As the charge gets larger the electrons
repel each other more and more and at the
same time are more and more attracted to
protons.
 Electrical Discharge: The build up of
electrons moving from one object to an
other

8. Electrical Discharge
 The larger the charge separation (dividing of
protons and electrons) the larger the electrical
discharge. You would be hurt more from lightning (a
large separation of charge) then from a carpet
shock (rubbing you feet on the carpet then touching
metal).

9. Van de Graaff Generator
 It builds up a charge of
electrons on the outside
of the sphere. A belt
rubs up on a wire brush.
The electrons repel each
other And you could
shock someone by
touching the VDG
releasing the charge.

10. Current Electricity

12. Electrical Currents
 Electrical Current: The steady flow of charged particles
 Unlike static electricity, an electrical current flows
continuously, as long as two conditions are met.
 Electrical Current:
 Requires an energy source
 It will not flow unless it has a complete path or circuit for the
charged particles to flow through.

13. Electrical Currents
 Amperes (A): The rate at which an electrical
current flows. Often called “Amps”
 Most electrical devices around your home have a current
of less than 15 A. For example, the current through an
ordinary 60-W light bulb is 0.5 A. Microwave ovens
usually use between 5 and 8 A, and electric kettles usually
use 13 A. In contrast, a digital wristwatch uses a current
of only a tiny fraction of an ampere, while a generating
station produces many thousands of amperes.

14. Electrical Currents
 To move the charge
from where it is
produced to where it is
needed they use
conductors. Conduction
of electricity through
wires allows for the
transfer of electrical
energy from place to
place.

15. Circuits
 Circuit: a path that controls the flow of electricity
 In most electrical circuits, the path that the electricity flows along is
made of solid metal wires. But circuits can also include gases, other
fluids, or other substances.
 A circuit usually includes a conductor, an energy source, and a
load.

16. Circuits
 A circuit usually includes a conductor, an
energy source, and a load.
 Load: a device to convert electrical energy
to another form of energy. Example, the
light bulb is the load. It converts electrical
energy to light and heat.

17. Electrical Energy
 Electrical energy: is the energy carried by
charged particles
 Voltage:
 is a measure of how much electrical energy each
charged particle carries.
 The higher the voltage is, the greater the
potential energy of each particle.
 The unit of voltage is the volt (V)
 The simplest way to measure voltage is with a
voltmeter

18. Electrical Safety

19. Electrical Safety
 No one wants to get shocked, but some
electrical shocks are worse then others.
 Short Circuit: is an unintended path taken
by electricity. Most of the time it is the
path of least resistance.

20. Dangers of Electric Shock
 Voltage vs. Amperage
 High voltage is more dangerous then low voltage 50,000 V are
more likely to kill you then 10 V
 BUT
 Amperage is much more dangerous then voltage. You would feel
0.015A and as little as 0.1A could KILL YOU.
 Insulators like wood, rubber or air make it harder for electrons to
flow through them and so the protect us from shock.

21. 7 steps to Electrical Safety
 1. Keep it dry: Keep electrical devices dry and away from water.
 2. Don’t use damaged electrical devices: Frayed or broken cords are dangerous.
Only use proper plug in outlets.
 3. Unplug: always unplug an electrical device before looking inside or fixing it.
 4. Stay away: Stay away from over-head power lines.
 5. Use safety features: don’t bypass safety features or remove the ground prong
from cords.
 6. Don’t over load: Don’t plug to many things into one outlet.
 7. Pull the plug: When unplugging a device pull the plug at the wall not on the
cord.

22. Electrical Safety Devices
 Grounded 3-prong plugs: The 3rd prong
goes to the ground so the charge will
short circuit to the ground not you.
 Fuses and circuit breakers are safety
devices that break the flow of electrons
through the circuit if the current gets to
high.

23. Dangers of Lightning

24. Cells & Batteries

25. Cells & Batteries
 Electrochemical Cell: A device that converts chemical energy into
electrical energy and produces direct current.

26. Electrochemical Cell
 Electrochemical Cell:
 They have two
electrodes made of
different metals, and
a conducting electrolyte
(that can form ions).

27. Electrochemical Cell
 A chemical reaction happens in a cell, where
the electrons are removed from one
electrode by the electrolyte and are sent to
the other electrode.
 The electrodes are connected to terminals.
The “+ terminal” is connected to the
electrode that lost its electrons and the “-
terminal” is connected to the electrode that
gained electrons.

28. Electrochemical Cell
 There are 2 types of
electrochemical cells: dry and wet
cells
 dry cells have a pastefor an
electrolyte
 wet cells have a liquid electrolyte
(usually a strong acid, which
makes them dangerous)

29. Electrochemical Cell
 Primary Cell: chemical reaction is
irreversible and you throw them
away when they die
 Secondary Cell
(Storage/Rechargeable Cell): can
be restored by using another
source of electricity (electrons
can flow in the opposite
direction)

30. Batteries
 Battery: a combination of several
cells that are sealed in a case with
only 2 terminals instead of a pair
of terminals for each cell
 9 volt and the 6V flashlight
“batteries” are true batteries.
The common AA, AAA, C and D
size “batteries” are single cells –
not batteries.

31. Electroplating

32. Electroplating
 Electrochemistry: the study of chemical processes that cause
electrons to move. It is the study of chemical reactions that create
electricity.
 Electroplating: using electrochemical reactions to deposit a very
thin layer of metal onto the surface of another material.

33. Controlling the Flow

34. Insulators & Conductors
 Insulators: Electricity does not easily flow through this material
 Conductors: Electricity easily flows through this material.
 Why does this happen?

35. Insulators & Conductors
 Insulators have electrons that are very
closely bonded to their nucleus. Because
the electrons are closely bonded they do
not transfer very easily and so they don’t
move a charge very well.
 Conductors have electrons that are loosely
bonded to their nucleus. Because of this
they quickly and easily transfer electricity.

36. Insulators & Conductors
 “Superconductors” They are perfect conductors - they have no
resistance to electron flow.

37. Insulators & Conductors
 SUPERCONDUCTORS ARE USED FOR:
 Transport vehicles such as trains can be made to "float" on
strong superconducting magnets, virtually eliminating
friction between the train and its tracks. Japan has done
much work in this area.
 Magnetic Resonance Imaging (MRI) use superconductors
to produce images more quickly. Superconductors are used
in generators and in the storage and transmission of
electricity.

38. Resistors
 Engineers need to know how well different
materials conduct electricity so they can design both
safe and effective devices.
 In some applications a conductor is called a resistor.
 A resistor allows electrons to flow through it
but provides resistance to it. This means it is harder
for electrons to flow through the device.
 Resistance is measured in Ohms.

39. Resistors
 So why do we need resistors?
 A light Bulb is a resistor.
 So is an electric heater.
 And a lie detector.

40. Resistors
 The volume control on a stereo is a special kind of resistor called a
variable resistor or rheostat.
 An additional example of a rheostat is a light dimmer.
 Variable Resistor or Rheostat: Resistor that can change the amount of
resistance provided

41. Water Model

42. Water Model
 What is resistance and what is its unit of measurement?
 Resistance: describes the forces that slow the flow of electron current
in a conductor. Measured in ohms

43. Water Model
 Because we can not easily see electricity moving through conductors it
is best if we can describe electricity using a model.

44. Water Model
 Flowing water is an excellent comparison of electrons flowing in a
circuit.

45. Water Model
 Water in a pipe can flow quickly or slowly.
 This is most similar to the measure of current.
 High current = fast electron flow or a large amount of
electron flow.

46. Water Model
 Current is the amount of electrons that flow past a given
point every second and is measured in Amperes/amps (A) If
we picture electrons in a wire flowing like water in a pipe
what factors would allow more water/electrons to flow?

47. Water Model
 Current in a pipe or a wire. What will move more fast or
more easily?
 Narrow pipe vs. Wide pipe
 Wide Pipe
 Short pipe vs. Long pipe
 Short Pipe

48. Water Model
 Pressure is what moves water through pipes. What is forcing
the electrons down a pipe?
 Voltage/Potential difference is the force that pushes
electrons. Voltage is measured in volts (V).

49. Water Model
 Water in a pipe is slowed by the
walls, in a river rocks and debris
will slow the flow.
 Resistance is the slowing of
electron flow by friction between
the electrons and the atoms.
Resistance is measured in ohms Ω.

50. Ohm’s Law

51. Ohm’s Law
 Georg Simon Ohm did a lot of work with
electricity in the 1800’s He found links between
voltage, current & resistance. He was able to
form a law (Ohm’s law) regarding resistance.
 If the resistance of a conductor stays constant,
then the current is directly proportional to the
voltage applied.

52. Ohm’s Law
 Devices that measure electricity:
 Voltmeters - measure voltage (in volts V)
 Milivoltmeters – tiny amounts of voltage (in mV)
 Ammeters measure - current (in amps A)
 Galvanometers measure - tiny amounts of current ( in
mA)
 Resistometers or Ohmeters measure - resistance (in
ohms Ω)
 Multimeters – measure voltage, amps, and resistance

53. Ohm’s Law
 How can we graph the
relationship between current and
voltage?
 Draw the Graph

54. Ohm’s Law
 Ohm’s law does not work if there is a change in
temperature. When the temperature pf a resistor changes,
then its resistance changes,
 Resistance is lowest when a conductor is cool. As the
temperature increases the resistance increases.

55. Ohm’s Law
V = I x R
V = Voltage
I = Current
R = Resistance

56. Ohm’s Law

57. Ohm’s Law

58. Ohm’s Law
 Need to Know!
 1 amp = 1000 milliamperes
 1 volt = 1000 millivolts

59. Ohm’s Law
 Let’s try some!
1. A 30 V battery creates a current through a 15 Ω resistor.
How much current is created?
V = I x R
I =
𝑽
𝑹
I =
𝟑𝟎
𝟏𝟓
I =2

60. Ohm’s Law
 Let’s try some!
2. A motor has an internal resistance of 40 Ω. The motor is in a
circuit with a current of 4.0 A. What is the voltage?
V = I x R
V = 4.0 x 40
V = 160 V

61. Ohm’s Law

62. Schematic Diagrams

63. Schematic Diagrams
 Schematic or Schematic Diagram: A drawing made with special
symbols that show the components and connections of an
electrical circuit clearly

64. Schematic Diagrams

65. Schematic Diagrams

66. Schematic Diagrams

67. Schematic Diagrams

68. Schematic Diagrams

69. Schematic Diagrams
 What are the four basic parts of a circuit?
Source
Load
Conductor
Switch

70. Schematic Diagrams
 What are the four basic parts of a circuit?
Source
Load
Conductor
Switch

71. Schematic Diagrams
Draw & describe this
schematic diagram

72. Schematic Diagrams
Draw & describe this schematic diagram
9V battery
3 Resistors 10 Ohms each
Conductor connector

73. Schematic Diagrams
Draw & describe this
schematic diagram

74. Schematic Diagrams
Draw & describe this schematic diagram
Battery
Conductor
Rheostat
Ammeter
Voltmeter
Resistor

75. Schematic Diagrams
 Draw Open vs. Closed Circuit

76. Schematic Diagrams
 A student determined that the toy moves forward when
its switch is moved to the left and backward when the
switch is moved to the right. In its middle position, the
switch turns the toy off.
 A bulb on top of the toy lights up when it moves in either
direction.
 She determined that it has two loads, a motor and a bulb.
She also found two 1.5-V cells that act as the source and
a switching mechanism that appears to connect the ends
of four wires.
 Beside are 2 schematics showing the circuits for forward
and backward movement of the toy.

77. Parallel vs Series Circuits

78. Series Circuits
 Series Circuit:
 The circuit in which the current passes through each bulb in turn
 Only 1 pathway for the current
 If that pathway is interrupted, the whole circuit cannot function.
 Adding components increases the total resistance of the circuit. This
decreases the current. Thus, adding an extra bulb to a series string of
lights makes all the bulbs dimmer.

79. Series Circuits
 Series Circuit:
 However, series circuits do have
an important use. In household
circuits, switches are wired in
series with other components (e.g.,
wall plugs, lights). This makes it
possible to turn off all the
electricity in the circuit.

80. Parallel Circuits
 Parallel Circuit:
 Has a separate current path for each section of the circuit
 An interruption or break in one pathway does not affect the rest of
the pathways in the circuit.
 Adding a new pathway with more resistors does not affect the
resistance in any of the other pathways.

81. Parallel Circuits
 Parallel Circuit:
 In a parallel-wired string of lights, for
example, each bulb has its own path to the
current source.
 adding extra resistors in parallel decreases the
total resistance of the circuit. This might seem
strange, but remember that adding more paths
for the current to take means less total
resistance. Think about how much less
resistance there is when you drink through two
straws instead of one.

82. Parallel Circuits

83. Series vs Parallel Circuits
 Think of String or Christmas
Lights! Do we want them in a
series circuit of parallel
circuit?
 Parallel! If one burns out the
rest won’t go out

84. Series vs Parallel Circuits

85. Series vs Parallel Circuits
 Household wiring, Series or parallel?
 Household wiring is one of many applications that use parallel circuits.
You wouldn’t want the power to your refrigerator to go off if a bulb
burnt out, would you?

86. Series vs Parallel Circuits
 Transistor:
 used for tiny circuits, referred to as solid-state
components because they are made of a solid
material with no moving parts.
 Have 3 layers so that a small voltage through
the middle layer controls a current between the
outer layers.
 Can act like switches

87. Series vs Parallel Circuits
 Microcircuits/integrated circuits:
 made up of microscopic transistors
and resistors