Download Electricity 15

Electricity 15-16
3. Electricity
3.1 Module OSH10030
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1. Electricity - Part 1
1.1 Module OSH10030
1.2 Learning Outcomes
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1.3 Electricity
1.4 Part 1
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1.5 What is Electricity?
1.6 Electron / Electricity Flow
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1.7 Electron / Electricity Flow
1.8 Voltage
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1.9 Current
1.10 Resistance
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1.11 Ohm's Law
1.12 Electrical Circuit
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1.13 Direct Current (DC)
1.14 Alternating Current (AC)
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1.15 Alternating Current (AC)
1.16 Three Phase Alternating Current
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1.17 Static Electricity
1.18 Electrical Arcing
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1.19 Summary
1.20 Electricity
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2. Electricity - Part 2
2.1 Module OSH10030
2.2 Electricity
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2.3 Part 2
2.4 Electrical Hazards
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2.5 Electrical Shock
2.6 Alternating Current (AC)
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2.7 Physiological Effects of Electric Shock
2.8 Electrical Supply
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2.9 Electricity Supply
2.10 Live Contact
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2.11 Live Contact
2.12 Live Contact
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2.13 Live Contact
2.14 Switch
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2.15 Switch
2.16 Switch
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2.17 Bird on the Wire
2.18 Don't Try this at Home!
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2.19 Earthing / Bonding
2.20 Fuses
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2.21 Miniature Circuit Breakers
2.22 Fuse
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2.23 Fuse
2.24 Residual Circuit Device (RCD)
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2.25 Residual Circuit Device (RCD)
2.26 Residual Circuit Device
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2.27 Live / Neutral
2.28 Live / Neutral
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2.29 Electrical Distribution Board
2.30 Step Down Transformer
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2.31 Basic Electrical Safety
2.32 Basic Electrical Safety
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2.33 Basic Electrical Safety
2.34 Basic Electrical Safety
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2.35 Basic Electrical Safety
2.36 Basic Electrical Safety
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2.37 Lecture Summary
4. Introduction Video
4.1 Introduction Video
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5. Contact information
5.1 Contact information
6. Concluding Video
6.1 Concluding Video
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7. Self Assessment Questions - Part 2
7.1 SAQ 2.1
(Multiple Choice, 10 points, unlimited attempts permitted)
Correct
Choice
Always
X
Sometimes
Never
Feedback when correct:
Whilst an RCD will significantly reduce the risk of electric shock there are scenarios in which an
RCD will not protect against electric shock.
If a person comes into contact with both the live and neutral phases at the same time whilst
they are insulated from earth electric current will flow from the live phase through that person's
body and back through the neutral phase, however, no electricity will be lost to earth. Therefore
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there will be no imbalance between the live and neutral phases of the supply and the fault will
not be detected by the RCD. This could lead to a significant shock being received.
Feedback when incorrect:
Actually it’s 'sometimes', go back and see why.
7.2 SAQ 2.2
(Fill-in-the-Blank, 10 points, 1 attempt permitted)
Choice
With currents over 30 mA there is the possibility of cardiac arrest.
30
Thirty
Feedback when correct:
That's right! Well done.
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30 mA is correct
Feedback when incorrect:
No, that's not right; was it a guess? Have a look at the notes or back through the lecture for the
correct response
7.3 SAQ 2.3
(Multiple Choice, 10 points, unlimited attempts permitted)
Correct
Choice
X
The equipment
Personnel who may come in contact with the equipment
Both
Neither
Feedback when correct:
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Well done, that’s right.
Feedback when incorrect:
No, try again!
7.4 SAQ 2.4
(Multiple Choice, 10 points, 1 attempt permitted)
Correct
Choice
When an electrical cable hangs down between two poles in the shape of an arc
A phase in the electrical cycle
A serious long term effect when acids are liberated in the blood after electric
shock
X
When electricity jumps across an empty space
Feedback when correct:
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Well done, that’s right.
Feedback when incorrect:
No, that’s not correct; have a look at the notes or the relevant slide in Part 1 of the lecture for
the right answer.
7.5 SAQ 2.5
(Multiple Choice, 10 points, unlimited attempts permitted)
Correct
Choice
Feedback
Under normal circumstances electrical
No. Current will only flow through the
current will flow in the live, neutral and
earth wire if there has been a short
earth wires of standard domestic
circuit. Try again.
wiring.
You can only get an electric shock if you
No. You CAN get an electric shock from
touch the live wire in an electrical
touching the neutral wire. Try again.
circuit and not when you touch the
neutral wire
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X
Under normal circumstances electrical
That's right. Under normal
current will flow only in the live and
circumstances electrical current will
neutral wires of a domestic plug.
only flow in the live cable / phase and
the neutral cable / phase of an
electrical circuit.
The amount of electricity flowing in
each phase is always the same, hence it
is possible to receive a shock from
either wire / phase.
Current will only flow in the earth wire
if there has been a short circuit and
electricity has been lost from the
intended pathway, flowing to earth
down the earth wire.
8. Self-Assessment Questions - Part 1
8.1 SAQ 1.1
(Multiple Choice, 10 points, unlimited attempts permitted)
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Correct
Choice
X
AC
DC
Feedback when correct:
Yes, well done! The constantly changing nature of an AC supply can lead to the disruption of
heart rhythms if an AC supply passes across the chest area. It can also give rise to an inability to
let go of the source of shock in persons who are in direct contact with an AC supply.
These are not associated with DC shocks and explain why an AC supply at a given voltage is
more dangerous than a DC supply of the same voltage. At a given voltage, say 100v, the DC
supply is a constant 100v, whereas the AC supply actually peaks at much higher (approx. 140v)
as when we are talking about AC voltages we are referring to average / root mean square
voltages.
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In addition, when three Phase AC supply is used, three pulses or phases of AC are supplied at the
same time, resulting in a much greater voltage and consequently a much greater risk to safety.
Feedback when incorrect:
I’m afraid not. Go back and click on A) to see the correct answer
8.2 SAQ 1.2
(Multiple Choice, 10 points, unlimited attempts permitted)
Correct
Choice
Feedback
X
When electricity meets resistance in a
That's right, well done. When
circuit this generates energy in the form
electricity tries to flow through a
of heat, thus giving rise to burns along
material with high resistance energy in
the path that the electricity takes
the form of heat is created. This is
through the body.
because as the electrons try to move
through the material they are
constantly colliding with the material's
atoms, generating energy. It is this
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energy that causes a light bulb to light,
a kettle element to heat water and for
your body to burn when receiving an
electric shock.
The resistance to flow encountered in
Afraid not, try again
the body will cause the Residual
Current Device to trip due to Ohms
Law.
The higher the body's resistance to
Afraid not, try again
electricity the less risk of a shock being
experienced.
8.3 SAQ 1.3
(Multiple Choice, 10 points, unlimited attempts permitted)
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Correct
Choice
Feedback
X
Electricity will only flow between two
That's right. Ohms law states that in an
points when there is a voltage
electrical circuit the voltage always
difference between those two points.
equals the current multiplied by the
resistance - V = C*R.
Voltage is a measure of the force which
motivates electricity to flow from an
area where there are a higher amount
of electrons to an area where there are
fewer (the earth). If the voltage is zero,
then electricity will not flow
At any given voltage DC is more
That's not right, try again
hazardous than AC
Electrons are used up when electricity
That's not right, try again
is used to power equipment
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