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Engineering Skills: Electrical/Electronic – Intermediate 1
Answers
Materials
Number & Name Accessory
Ferrous Non-ferrous
Non-metallic
13A domestic
plug top


5A one way
switch


Ceiling rose


13A switch
socket


Lamp holder


One of the biggest disadvantages of ferrous materials is that they can rust or
corrode and this is not really something you want in your lighting switch or lamp
holder. Rust and/or corrosion will cause damage to the accessory and will
eventually cause an open or short circuit.
The table above shows that most of the electrical accessories that we use are
made from a combination of non-ferrous and non-metallic materials. Even the
switch and the switch socket fixing screws are made from an alloy that is nonferrous.
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Engineering Skills: Electrical/Electronic – Intermediate 1
Tools
Screwdrivers
There are several types of screwdrivers:
Electricians’ Screwdrivers
These normally have round blades with either parallel or
flared tips. The handle is always made of an insulating
material and the blade is often sheathed in plastic so that
only the tip is exposed. Sometimes a neon indicator is
incorporated into the handle as a safety device so that
live voltage sources can be detected safely. The tip is
slotted and is mainly used for connections in terminal
strip, lighting switches and sockets.
Slotted Screwdrivers
Slotted screwdrivers are for use on slotted screws and
have a flared tip on the end of a round or square section
blade.
They are available in lengths up to 450mm with tip widths of 10mm. Normally the
wider the tip means a longer blade and larger handle.
However special purpose screwdrivers are available with
wide tips and short blades – these are usually called stumpy
screwdrivers.
Crosspoint Screwdrivers
There are several types of crosshead screw in use, the most common of which
are “Phillips” and “Pozidrive”. The screws are made so that the screwdriver is
located securely into the head. It is important that the correct screwdriver is used
with the relevant screw as the heads are easily damaged and can be particularly
difficult to remove.
Screwdrivers should not be used if the tip
becomes damaged because it will not fit properly
in the screw head.
Screwdriver handles are normally made from
wood or plastic.
NB
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Screwdrivers are NOT chisels.
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Engineering Skills: Electrical/Electronic – Intermediate 1
Pliers
Pliers are gripping tools that are used to hold components that would otherwise be
difficult to hold and control. They are made from forged steel with hardened and
tempered jaws to resist wear. There are six common types of pliers.
Flat nosed pliers:
Flat nosed pliers are basic pliers used for gripping
and holding.
Combination pliers:
Combination pliers are more versatile than flat nosed pliers and incorporate side
cutters (for cutting wire), a pipe grip and joint cutters.
Electrical pliers:
Electrical pliers are similar to combination pliers but
with heavily insulated handles to withstand high
voltages.
Pin nosed pliers:
Pin nosed pliers are more delicate than the heavier
pliers and are used for holding or bending small
components where access may be limited.
Round nosed pliers:
Round nosed pliers are used for holding, bending, securing and where access is
limited.
Pliers should never be used to tighten or undo nuts or bolts as the heads of
the nuts etc will be damaged by rounding the corners.
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Multi-purpose Pliers – these include circlip pliers, wire strippers, side cutters:
Side Cutting Pliers or Snips – are used a lot in
electrical/electronic circuit construction to trim/cut
cables.
Snips should only be used to cut cables, copper wires etc.
Wire Strippers (automatic)
There are many types of wire strippers from
those used for stripping single core to others for
stripping twin and earth. Usually a wire stripper
strips the insulation from the cable leaving the
copper conductor exposed. The automatic
strippers shown were also known as Yankee
Strippers because of their origin.
Wire Strippers
Both types of wire strippers are a ‘cut and pull’
type of stripper.
Electrician’s Knife
In some instances a specially designed electrician’s knife may be used for
stripping insulation. A ‘Stanley’ knife should never be used for this job as it has an
extremely sharp blade. An electrician’s knife is usually quite blunt, to lessen the
chance of damage to the copper conductor.
Notice how blunt the knife is.
Please note that this knife is a tool and as such would be kept in a tool box.
It is an offence to carry a knife.
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Crimping Pliers
Crimping is commonly used to clamp (crush in a way) terminals to cable ends.
This gives the cable a robust connection that is both electrically and mechanically
strong and long lasting.
The crimped end can also be
connected and reconnected many
times without loss of mechanical
strength and electrical conductivity.
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General Workshop Tools
The following are the main hand tools you will find in all engineering workshops.
Your instructor will show you how to use the tools and explain any special safety
requirements.
Saws
A hand saw used to cut metal or plastic is known as a
hacksaw and comes in various sizes, such as a junior
hacksaw. The main type of hacksaw consists of a frame
and a blade. The frame is adjustable to allow different
sizes of blade to be inserted. The blade must be
tensioned and inserted correctly.
Blades are classified by the number of teeth per unit length. The greater the
number of teeth the finer the cut. Normally thick materials are cut with a coarse
blade and thin materials with a finer blade. When cutting, the whole length of the
blade should be used. The hacksaw blade should never be used without the
frame.
Junior hacksaws are not adjustable and the blade is
tensioned by the spring of the frame.
The pad saw is different from hacksaws because it only has a handle and a
blade. The blade is a narrow strip of steel which has cutting teeth on one side and
this tool can be used in awkward or confined spaces.
The pad saw might be used for cutting thin metal but
more often it is used to cut shaped holes in wood or
plasterboard.
Footprints
A ‘footprint’ is a gripping tool that can be adjusted to have a narrow or
wide grip and is used to hold and turn metal conduit or couplings.
It has serrated (grooved) jaws and will leave a noticeable mark if used
wrongly.
It gets its name from the trademark small ‘footprint’ symbol imprinted
on each tool.
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Adjustable wrench
Similar to a footprint, an adjustable wrench can be adjusted to
different jaw sizes to grip and turn.
This tool may also be found in a plumber’s tool kit and is
sometimes called ‘water pump pliers’.
Plumbers and electricians use them mainly to tighten decorative
chrome or ‘bright’ metal fittings.
Files
A file is used to remove material from the work piece.
Various types are available and can be used to
complete a work piece accurately with a good finish.
A file should never be used without a handle as the
end of the file, or tang, is sharp.
Flat File
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Half-Round File
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Engineering Skills: Electrical/Electronic – Intermediate 1
Hammers
Hammers are important tools that must be used
correctly and safely. They have a number of uses
such as: shaping metal; driving things into
position; tapping marking tools.
Hammers are available in a wide range of weights
from 200grams to 900grams.
Bigger hammers are known as sledge and lump hammers and
are used for heavy work.
Hammer handles or shafts are usually
made of wood but some are now made
of plastic. These materials absorb the
shock when striking.
You should never strike one hammer with another as bits may
chip off and damage your skin. When using a hammer you
shouldn’t look at the hammer itself but at the end of what is being
struck. This should help you not to hit your thumb!
A mallet is a hammer in the loosest sense. This tool is
used for the forming and shaping of sheet metal and is
usually made from boxwood or hide. This allows metals
with polished surfaces to be worked without undue surface
damage. Mallets come in different forms depending on the
use.
Chisels
Basic cold chisels are used in both engineering and
construction to remove excess material or to split material.
The bolster chisel is used by electricians to split
floorboards along the tongue and groove to gain access
under floors to wiring.
In many cases now the modern electrician would simply use
a quickcut.
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Activity: Tool Identification
The table below shows you a selection of tools – fill in the table with what you
think they are called.
Tool
Tool Picture
Tool Name
Tool 1
Tool 2
Tool 3
Tool 4
Tool 5
Tool 6
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Engineering Skills: Electrical/Electronic – Intermediate 1
Answers
Tool Identification
Tool
Tool Picture
Tool Name
Junior Hacksaw
Tool 1
Electrician’s Screwdriver
Tool 2
Tool 3
Cable Strippers
Tool 4
Floorboard Chisel
(Bolster)
Tool 5
Side Cutters
Snips
Cable Cutters
Tool 6
Combination Pliers
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Activity: Tool Su-Doku
Each group of 6 boxes below must contain each of the listed tools, but also each
line across and up and down must contain each of the 6 tools.
Hammer
Crimpers
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Snips
Pliers
Strippers
Screw
driver
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Engineering Skills: Electrical/Electronic – Intermediate 1
Answers
Tool Su-Doku
Hammer
Crimpers
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Snips
Pliers
Strippers
Screw
driver
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Engineering Skills: Electrical/Electronic – Intermediate 1
Diagrams
In electrical and electronic circuitry there are different types of diagrams:
We will look at the following types of diagram:

layout

wiring

circuit

block.
Layout Diagram
Component Position
These diagrams show the physical position of each
component or circuit accessory. This type of diagram
shows only the location of a switch or relay or resistor and
does not show any interconnections or wiring details.
This type of diagram is widely used in the installation of
new circuits and in the maintenance and repair of
circuits.
SW 1
R4
R1 R2 R3
Tr1
Tr2
D1
D2
C1
C2
Wiring Diagram
Cabling and Connections
Wiring diagrams show the route the cabling or wiring
actually takes and would possibly give the connection details
as well.
Wiring and layout diagrams are the most widely used for the
installation of circuits whether it is for an aircraft, a motor
car or a new house.
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Circuit Diagram
How the Circuit Operates
Circuit diagrams show all the components
and interconnecting wiring without any details
of cable routes or component positions. This is
the most widely used diagram for fault finding
and repair of circuits.
Circuit diagrams show how the circuit operates without showing the physical
layout.
Block Diagram
Supply
Socket
Socket
Circuits in Block Form
A block diagram is a simple diagram in which a circuit or system is split into
simple blocks that are labelled with the function of the block.
Wires Crossing/Connection Convention
Wires Connected
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Wires Crossing
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Engineering Skills: Electrical/Electronic – Intermediate 1
Current – Voltage – Resistance
The relationship between current, voltage and resistance is important to all
electrical engineers.
Current
Voltage
Resistance
Symbol
I
V
R
Unit
Ampere (A)
Volt (V)
Ohm (Ω)
What exactly are voltage, current and
resistance?
This is a picture of the Hoover Dam.
Current (symbol I) is like the water flowing from
the overflow valve in the side of the dam.
Voltage (V) can be likened to the pressure of
water. The more water in the dam - the more
pressure pushing water out. It’s the same with
voltage: more voltage = more current.
Resistance (R) in this case is the size of the
opening of the overflow valve. If the valve is
slightly open then the flow pressure would be
high and if the valve is fully open the flow
pressure would be lower.
Apply this to an electrical circuit:
Current (I) is what flows through a wire or conductor like water flowing out of
the dam. Current flows from points of high voltage to points of low voltage through
the conductor. Current is measured in amperes (A). Ampere is shortened to amp.
Voltage (V) or sometimes (E) is the difference in electrical potential between two
points in a circuit. It's the push or pressure behind the current flow through a
circuit, and is measured in volts (V).
Resistance (R) determines how much current will flow through a component.
Resistors are used to control voltage and current levels. A very high
resistance allows a small amount of current to flow. A very low resistance
allows a large amount of current to flow. Resistance is measured in ohms (Ω).
The relationship between V, I and R is stated in Ohm’s Law.
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Engineering Skills: Electrical/Electronic – Intermediate 1
Ohm’s Law
Ohm’s law states that, in an electrical circuit the current (I)
that flows is directly proportional to the voltage applied to
the circuit.
What this really means is that:
If the voltage increases
and
If the voltage decreases
the current increases
the current decreases
Georg Ohm
Also if the voltage remains constant (this is what happens in most circuits) then
the resistance and current are indirectly proportional.
What this means is that:
If the resistance decreases
and
If the resistance increases
the current increases
the current decreases
Anyway, try this with some simple figures:
If the voltage source remains constant at 100V look what happens to the current
as the resistance increases:
Voltage (V)
100V
100V
100V
100V
Resistance (Ω)
1Ω
10 Ω
100 Ω
1000 Ω
(1k Ω)
Current (I)
100A
10A
1A
0.1A
(100mA)
The relationship between voltage, current, and resistance is given by a simple
equation derived from Ohm’s Law. Fill in the blanks:
V = IR
V
Voltage = Current x Resistance
This will mean that:
I= R
Current = _________ ÷ ___________
and
R=
V
I
______ = _________ ÷ ___________
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Circuits
In any circuit, if there is a source of energy and a load, a current will flow. This
current flows through each component and this in turn creates a voltage drop
across each component.
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Activity: Electrical Symbols and Units
Complete the following table of electrical symbols and units
Current
Voltage
Resistance
Symbol
Unit
Ohm’s Law – Calculations
Ohm’s law states that, in an electrical circuit the current (I) that flows is directly
proportional to the voltage applied to the circuit.
Complete the table by applying that relationship:
Voltage (V)
Resistance (Ω)
150V
150V
150V
150V
1Ω
10Ω
100Ω
1000Ω
Current (I)
(1kΩ)
Remember the current = voltage divided by the resistance
Remember to write the units.
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Answers
Electrical Symbols and Units
Current
Voltage
Resistance
Symbol
I
V
R
Unit
Ampere (A)
Volt (V)
Ohm(Ω)
Ohm’s Law – Calculations
Ohm’s law states that, in an electrical circuit the current (I) that flows is directly
proportional to the voltage applied to the circuit.
Complete the table by applying that relationship:
Resistance (Ω)
1Ω
10Ω
100Ω
1000Ω
(1kΩ)
Voltage (V)
150V
150V
150V
150V
Current (I)
150A
15A
1.5A
0.15A or 150mA
Did you remember to write the units?
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Electrical Circuits
Common Domestic Circuit Types
Lighting
The most common lighting circuits used in houses
are one way lighting and two way lighting.
One Way Lighting
One way lighting is where a light is switched on and off by one switch
only.
A toilet usually is a common example of a one way lighting circuit. The
switch is near to the door and is switched on in the way in, and
switched off on the way out.
Two way lighting
Two way lighting is where a light can be switched on in one place and switched off
in another place.
A stairway is a common example of a two way lighting circuit. The light can be
switched on at the bottom of the stairs and switched off at the top of the stairs or
vice versa.
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Power Circuit Types
Power circuits in the UK are normally radial or ring.
Radial Circuit
A radial circuit is where power is transmitted from the supply to the first socket
then to the second, to the third etc and terminates at the last socket.
Socket 1
Socket 2
Socket 3
Supply
Radial Circuit
Ring Circuit
A ring circuit is where power is transmitted from the supply to each socket then is
connected back to the supply.
Socket 1
Socket 2
Supply
Socket 3
Ring Circuit
The ring circuit allows more power to be safely supplied to the circuit using the
same cable size as a radial circuit.
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Circuit Tests
There are many tests that will help us to check that the circuit does exactly what it
is supposed to do and in a safe manner. If the circuit works but goes on fire after a
short time then that is neither good nor safe!
One of the most basic tests that electrical/electronic engineers carry out on a
circuit is the continuity test.
Continuity Test
A continuity test checks the circuit to see that the circuit is a
complete loop.
A continuity tester can be:
 a meter that gives a reading
 audible like a high pitched sound, or
 a simple test lamp.
A good continuity test shows that the conductors are not broken and that all the
connections are at least reasonable. However, a continuity test, although useful, is
not enough to show that the circuit is totally safe so it would usually be used with
other tests.
switch
Continuity
tester
light
lights or
makes sound
In this case the circuit is good and the continuity tester lights or makes a
sound.
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switch
Continuity
tester
light
does not light
or make sound
bad connection at light fitting
In this case the circuit is not good and the continuity tester does not light or
make a sound.
The other useful task that a continuity test can do is to find the end of each cable if
you have a bundle of wires all the same colour.
Circuits Activity
Circuits can be more than just electrical circuits, so for this activity you must try to
list 4 circuits. Let’s start with a 400 metre athletics track.
1.
400 metre athletics track
2.
3.
4.
Hint - Think continuous circles!
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Answers
Circuits Activity
You might have thought of some of these:
1.
400 metre athletics track
2.
Satellite orbit of the earth
3.
Doughnut (jam ones don’t count)
4.
Roller coaster ride
5.
Go-kart racing track
6.
Bicycle wheel etc.
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Electrical Wires and Cables
Electrical wires and cables come in many forms and sizes and have a variety of
uses.
Wires are solid or stranded, insulated or un-insulated conductors.
For most applications, the main requirement of a cable is that it should carry a
specified electric current between two points in the most economical way. This
means we’re looking for a material that offers little resistance to the passage of
electricity to minimise energy loss along the cable length.
Silver is one of the best materials, but it cannot be used because it is too
expensive.
Copper is the most suitable in terms of carrying current and cost – it’s cheaper!
Aluminium, which is not as expensive as copper needs a larger size of conductor
to carry the same current – so it works out to be more expensive in the end.
Aluminium scores over copper mainly in weight saving, because it is lighter than
copper.
In the UK, aluminium conductors are usually only used for large fixed-installation
power cables for electricity distribution.
Although most wires are made of copper, it is worth remembering most metals will
conduct electricity.
Cables are insulated wires contained within an outer insulation or sheathing.
Cable Insulation
To prevent danger from electric shock and possible short-circuits, wires and
cables are covered in an insulating material.
In most cases, the cables used in this unit will be insulated with PVC.



polyvinyl chloride (PVC) – clean, easy to use,
cheap and resistant to corrosion. This is the
most widely used.
rubber – very cheap but prone to perishing
polytetrafluoroethylene (PTFE) – expensive but able to withstand high
temperatures.
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Engineering Skills: Electrical/Electronic – Intermediate 1
Wires and cables have many uses, for example:

electrical installations (ring mains, lighting)

flexible mains (kettle, vacuum cleaner)

data transmission (telephone, computer, TV).
The selection of the electrical cable is dependant on the following factors:
Cable Use
Cable Current
Cable Voltage
Cable Situation
Some of these are shown in the table below:
Cable Use
Motor Car
could be for…………
Current that might flow
House
Wiring
Small
Kitchen
Appliance
Large
could be……………
Voltage that will be
applied
Low
High
could be ………………….
Situation
Temperature
Vibration
Environment
choice of cable might
depend on………………..
This means that the type of electrical cable used in a motor car would not be the
same as the type of cable that would be used in the washing machine even
though both cables carry the same current - but not at the same voltage.
A co-axial cable that is used to connect the signal to the television is very different
from the electrical cable used to connect power to the kettle.
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Current Colour Codes
Single Phase:
Protective earth (PE)
Green/yellow striped
Neutral (N)
Blue
Live (L)
Brown
Wire types
Single strand wire
This type is used where rigidity is required or flexibility is not required. It can be
bent, but must not be used in applications where it will be flexed frequently
because this would cause it to break.
Multi-strand wire
Multi-strand is used where a flexible bend in the wire is required. It is classified by
the number of strands in the wire and the diameter (in mm) of each strand.
The difference is not only the voltage or current rating of the wire but also the
vibration and movement of the wire.
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Cable Types
Power Cables
Mains voltage is usually 230Volt in the UK and power cables are designed to
carry mains voltages and currents.
Mains Cables
Two-core and three-core power cables – usually called mains cables – are used
to connect appliances to the public mains supply via a 13A plug and socket.
Two-core cables have wires coloured brown (for live) and blue (for neutral).
Three-core cables have an additional green/yellow wire (for earth).
Since mains cables are normally subject to a lot of flexing and movement they
tend to be made up of stranded conductors rather than a solid conductor.
There is no vibration or movement in house wiring so single core, single conductor
can be used but usually it would be twin and earth.
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Signal cables
Signal cables consist of one or more conductors surrounded by a screen. The
screen is braided copper running the complete length of the cable.
It is used to isolate or screen the signal in the central conductor(s) from any
outside interference. It also provides security because the screen prevents any
radiation from the inner signal.
Multi-core screened cable
Coaxial cable
Coaxial cable is a screened cable with a single solid or stranded conductor
surrounded by layers of insulation and screening. Coaxial cable is used to connect
an aerial to the input of a television, and also as connecting leads for test
instruments such as oscilloscopes and signal generators.
Coaxial cable
Ribbon cable
Ribbon cable consists of a number of
single-core stranded wires joined together
lengthways in the form of a flat ribbon.
Ribbon cable provides a quick, simple and
cost-effective solution to mass termination. It
also has space and weight-saving advantages
over other wiring methods.
It is ideal for use on computers, peripherals,
interfaces, audio and digital equipment.
Coloured 10-way ribbon cable
Not all ribbon cable is multi-coloured.
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Cable Types and Crimped Terminals
Type
Picture
Use
PVC insulated
cables
sometimes
called Twin and
Earth
Mainly domestic
and commercial
premises. Used for
lighting circuits and
power circuits.
Single Core
(multi-stranded)
Industrial use for
circuits where the
wiring is subjected
to vibration or
movement.
Various colours

Domestic and
commercial uses
to connect
appliances such
as: computers,
kettles, X-boxes.

The 2-core version
has both its core
insulation and its
outer sheath made
of PVC.

Domestic and
commercial use to
connect signals to
television.
Multi-core
Flexible Cord
3 Core
Multi-core
Flexible Cord
2 Core
Coaxial
Crimp
Ring
Many applications:
Aerospace
Crimp
Spade
Automobiles
Crimp

Domestic
Appliances
Receptacle
Female Male
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