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BTEC Assignment BriefPearson BTEC Level 3 National Extended Certificate in Applied Science
Pearson BTEC Level 3 National Foundation Diploma in Applied Science
Qualification
Pearson BTEC Level 3 National Diploma in Applied Science
Pearson BTEC Level 3 National Extended Diploma in Applied Science
Unit number and title Unit 15: Electrical Circuits and their Applications
C: Examine AC and DC production and health and safety aspects in
Learning aim
domestic and industrial applications
Assignment title AC/DC
Assessor
Issue date
Hand in deadline
You are a trainee laboratory technician working for local aluminium
smelting works. The smelting works is a huge consumer of
electricity and has its own hydroelectric generating plant. The
hydroelectric plant sends excess electricity to the National Grid,
Vocational Scenario or which is in turn distributed to local homes. The plant also has an
Context induction furnace to produce aluminium ingots after the aluminium
has been smelted. As part of your training you have been asked by
the Health and Safety committee of the company to develop an
electrical safety awareness booklet for their employees.
Prepare a booklet titled ‘Electrical Safety Awareness’ that has the
following sections:
Section 1 – AC and DC current
Explain the differences and similarities of the properties of AC and
DC current in simple circuits
How are they produced? Use diagrams based on simple
Task laboratory experiments to illustrate.
Use laboratory based investigations to evaluate how to control
the AC electricity produced by generators. Apply the application
of Flemings’ rules to the operation of an electrical motor (left
hand) and the operation of an AC generator (right hand) to
explain the principles of a DC generator
Describe DC electricity can be stored.
Illustrate, with a fully labelled graph, the difference between
AC and DC electricity using an oscilloscope.
For AC compare the calculated root mean square (RMS)
and measured peak voltage to show the quantitative
relationship of RMS and peak values for AC electricity
Section 2 - Effects of AC and DC electricity on the human
physiology
In the context of the dangers of working with electricity, use a
, diagram of the body to illustrate specific points and supplementary
notes to explain:
The typical resistance values or current pathways in the
body. What are the implications of this and is it different for
AC compared to DC electricity?
The consequence of skin resistance in different conditions
e.g. in contact with the ground, when moist
The effect of the length of current exposure time and the
amount of electrical current. How is this different for AC
compared to DC electricity?
The safe levels of DC voltage
How the heart responds to electric shock and how is this
applied to the principles of a defibrillator
Section 3 - The National Grid
Evaluate, using diagrams, how AC electricity is produced in a
generator at the smelting works hydroelectric facility for use in homes
and industry. Apply the fundamental aspects of Fleming’s right hand
rule for the generator in the power station. You should include:
a reasoned argument as to why a high powered AC generator
should be used rather than a low powered AC/DC turbine.
Evaluate how the AC electricity is transferred from hydroelectric plant
to homes and industry. Mathematically account for the need for
transformers and high voltages. You should include:
the required voltage for applications of AC electricity around
the home and at the smelting plant.
the mathematical comparisons of energy/power loss of
transmitting electricity at different voltages
a reasoned argument as to why the voltages used to transmit
electricity through the national grid for a variety of uses have
been selected and why they may be different at different points
in the transfer system
a reasoned argument as to why certain components such as
transformers are required in specific parts of the national grid
and connections between the hydroelectric plant and the
National Grid.
4) Using AC and DC electricity around the home
Discuss the principles of the ring main circuit found in houses. You
should include:
what is the purpose of the residual current and earth leakage
circuit breakers (RCCB and ELCB), and how do they operate?
kettles and hairdryers are often ‘double insulated”, what is the
significance of this?
how do fuses work in domestic appliances and why are they
necessary?
when using DC equipment such as tablets, games consoles and
mobile phones, discuss the principles behind ‘charging them
up’ from the AC mains supply.
what are the dangers and inbuilt safety? (NB whilst these
questions give guidance to the range of considerations you
should discuss, you must present this in a coherent way.)
Section 5 - Using AC and DC electricity in industry
It is essential that the smelting works protects its workers by applying
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BTEC Internal Assessment QDAM January 2015
, the Electricity at Work Regulations 1989. Discuss the specific actions
that should be taken and the safety devices that should be used to
protect workers when operating and repairing the AC and DC
equipment in the plant.
Checklist of evidence An electrical safety awareness booklet that has the following content:
required An explanation of the differences and similarities of the
properties of AC and DC current in simple circuits;
A comparison of the route mean square (RMS) and peak
voltage for AC electricity in a simple circuit;
An explanation of the effects and dangers of AC and DC
electricity on human physiology;
An evaluation of the principles of AC production and
transmission for safe use in the context of providing AC
electricity for suitable uses in the home and aluminium
processing plant via the National Grid and its connection to the
hydroelectric facility;
A discussion of procedures and practices used to minimise risk
when working with electricity in the home and industry.
Criteria covered by this task:
Unit/Criteria
To achieve the criteria, you must show that you are able to:
reference
Evaluate the principles of AC production and transmission for safe use in suitable
C.D2
applications
C.M3 Compare RMS and peak values of AC electricity
Discuss procedures and practices used to minimise risk when working with
C.M4
electricity
C.P3 Explain the similarities and differences of AC and DC electrical circuits
Explain the dangers of working with electricity and its effects on human
C.P4
physiology
Sources of information http://www.hse.gov.uk/pUbns/priced/hsr25.pdf
to support you with
this Assignment http://www.inbrief.co.uk/employees/electricity-at-work/
https://van.physics.illinois.edu/qa/listing.php?id=6793
http://physicsnet.co.uk/a-level-physics-as-a2/current-electricity/
alternating-current-ac/
http://www.electricaleasy.com/2012/12/basic-construction-and-
working-of-dc.html
http://www.riotinto.com/aluminium-83.aspx#united%20kingdom
http://www.practicalphysics.org/explaining-rms-voltage-and-
current.html
http://www.homepower.com/articles/microhydro-power/design-
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BTEC Internal Assessment QDAM January 2015
, installation/electric-side-hydro-power
Centres are encouraged to include local employers in delivery by
asking them to give guest lectures and provide opportunities for
industrial visits and work experience.
Other assessment n/a
materials attached to
this Assignment Brief
P4: The dangers of working with electricity and its effects on human physiology
When electric current flows through the body it has certain effects on it. The effect of current on
the body depends on the level of the current; currents as low as thousandths of amps (milliamps)
can have adverse effects on the body. The table below shows physiological effects that electric
current has the human body at different levels.
Electric Current (1 second contact) Physiological Effect
1 mA Threshold of feeling, tingling sensation.
5 mA Maximum harmless current
10-20 mA Beginning of sustained muscular contraction
("Can't let go" current.)
100-300 mA Ventricular fibrillation, if continued can be
fatal. Respiratory function continues.
6A Sustained ventricular contraction followed by
normal heart rhythm. (defibrillation).
Temporary respiratory paralysis and possibly
burns.
P3: The similarities and differences of AC and DC electrical circuits
Voltage which leaves a battery is DC voltage. The voltage is constant and always flows in one
direction. The same is true for the current.
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,I = V/R
I = 9/3
I = 3A
Voltage which leaves an AC source has a frequency. In the UK it changes direction 50 times per
second. The frequency is 50Hz. The voltage also increases from zero to a peak voltage. On a graph
it would look like this
Peaks
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, If I ask you to calculate the current which voltage would I use 0, 9 or anything in between? 9V
We need to find an average somehow. We use something called the root mean square (RMS)
VRMS is related to the peak voltage.
V peak =√ 2 ×V RMS
The VRMS in the UK is 240 volts. Calculate the peak voltage.
Vpeak = √ 2× V RMS
Vpeak =√ 2× 240
Vpeak = 339.41
In the above AC circuit, the peak voltage is 9 volts.
To calculate the current through the circuit we need to use VRMS.
1. Calculate VRMS. 6.36
2. Calculate IRMS using the formula I = V/R. 2.12A
Vp
V RMS= =6.36V
√2
IRMS=6.36/3 =2.12A
Exercise:
Given VRMS calculate VP
1. 18v,
VP = √ 2× 18
VP = 25.46
2. 36v,
VP = √ 2× 36
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BTEC Assignment Brief v1.0
BTEC Internal Assessment QDAM January 2015
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