***Useful Information for Apprentices***

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Short-Circuit Currents & Interrupting Rating :-
To better Understand Interrupting Rating and the Importance of Compliance , ( Consider these Analogies )

* Normal Current Operation :
Flood Gates > Analogous to Overcurrent Protective Device ,
Reservoir Capacity Analogous to Available Fault Current .
Load > Current ( 100 Gallons per Minute )
Load / Overcurrent Protective Device )
► Available Fault Current / e.g. 50.00 Amps )

* Short-Circuit Operation with Inadequate Interrupting Rating :
Flood Gates > Are Destroyed because of Inadequate Interrupting Rating .
Dam / Breaks and Reservoir Releases Short-Circuit Current of ( 50.000 Gallons per Minute )
Load > Overcurrent Protective Device with Inadequate Interrupting Rating . in Violation of Overcurrent Protective Device is Destroyed .
► Available Fault Current / e.g. 50.00 Amps )

* Short-Current Operation with Adequate Interrupting Rating :
Flood Gates > Have Adequate Interrupting Rating . Fault Current Safely Interrupted .
Load > Overcurrent Protective Device with Adequate Interrupting Rating in Compliance / is Undamaged .
► Available Fault Current / e.g. 50.00 Amps )
► Short-Circuit Current Safely Cleared ,

 

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Basic Electrical Theory Revision :-
Résistance .
This is the Opposition to the flow of current in a conductor determined by its length, Cross Sectional Area and Temperature .

Power :-
This is the product of current and voltage , hence P = I X V :
Relationship between voltage, current and Résistance :-
Voltage = Current x Résistance V = I x R or ,
Current = Voltage / Résistance I = V/R or ,
Résistance = Voltage / Current R= V/I ,

Common Multiples of Units :-
Current I amperes kA ( kilo-Amperes , 1000 Amperes :- mA ( milli-Amperes , 1/1000 of an Ampere ,
Voltage V volts kV ( kilovolts 1000 volts :- mV millivolts 1/1000 of a volt ,
Résistance R Ohms MΩ . megohms 1.000.000Ω :- mΩ milli-ohms 1/1000 of an Ohm ,
Power P Watts MW megawatt 1.000.000 watts :- kW kilowatt 1000 watts ,

R total = R1 + R2 + R3 + R4 , R1/1Ω : R2/2Ω : R3/10Ω : R4/4Ω ( R total = 1 + 2 + 10 + 4 = 17Ω )

1) 85m of 1.0mm2 Conductor ,
2) 1m of 6.0mm2 Conductor ,
3) 25m of 4.0mm2 Conductor ,
4) 12m of 0.75mm2 Conductor ,

1) 1.0mm2 is 19.5 mΩ/m . so , 85m would be ( 19.5 x 85 ÷ 1000 = 1.65Ω :
2) a 6.0mm2 Conductor would have a résistance 6 times less than a 1.0mm2 Conductor . i.e. ( 19.5/6 = 3.25mΩ :
3) 25m of 4.0mm2 would be 19.5 x 25/4 x 1000 = 0.12Ω :
4) 12m of 0.75mm2 would be 19.5 x 12/0.75 x 1000 = 0.312Ω :

 

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Verification and Certification
The quality of visual inspection is dependent on the experience and knowledge of the person carrying out the inspection. It is vitally important that this person understands the Regulations .

Visual inspection should precede testing with instruments and must of course be prior to the installation being made live. It may be necessary to inspect some parts of an installation during the construction phase as these parts may be concealed later. A checklist for a Domestic Installation might read as follows:

1. Correct type.
2. Correct voltage rating.
3. Correct current rating.
4. Correct colour coding.
5. Diversity correctly applied.
6. Permitted volt-drop not exceeded.
7. Protected against mechanical damage and abrasion.
8. Not exposed to direct sunlight or, if so exposed, of a suitable type.
9. Correctly selected and installed for use on exterior walls etc.
10. Internal radii of bends in accordance .
11. Correctly supported in accordance .
12. Not used for connection of equipment which can be moved.

 

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2.1 Unit 201 Working effectively and safely in the electrotechnical environment (Stage 1)
Q1 Which of the following documents is non-statutory
a Health and Safety at Work Act
b Electricity at Work Regulations
c COSHH
d BS 7671 Requirements for Electrical Installations.
Q2 Prior to using an electric saw on a construction site, a user check finds that the insulation on the supply flex is damaged. The correct procedure would be to
a replace the cord with a new one
b report the damage to a supervisor after use
c repair the cord with insulation tape
d report the damage to a supervisor before use.
Q3 When carrying out repairs to the base of a street lighting column it is essential to wear
a a safety harness
b high visibility clothes
c gauntlets
d high voltage clothing.
Q4 First aid points are indicated using signs bearing a white cross on a
a yellow background
b blue background
c red background
d green background.
Q5 The type of fire extinguisher which would not be suitable for flammable liquids is
a dry powder
b water
c carbon dioxide
d foam.
Q6 CO2 fire extinguishers are indicated by the colour code
a black
b red
c beige
d blue.
Q7 An independent regulatory body responsible for monitoring standards of electrical installation contractors is the
a Electrical Institute Council
b Institute of Electrical Engineers
c National Electrical Contractors Institute Inspection Council
d National Inspection Council for Electrical Installation Contractors.
Q8 To ensure that a particular item of electrotechnical equipment meets a particular British Standard or BSEN Harmonised Standard, the best source of information would be the
a manufacturer of the equipment
b British Standards Institute
c Institute of Electrical Engineers
d supplier of the equipment.

 

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Q9 Using a scale of 1:50, a 10 mm measurement taken from a plan would be equal to an actual measurement of
a 5 mm
b 5 cm
c 0.5 m
d 5 m.
Q10
Figure 1 shows the BS EN 60617 symbol for a
a one gang switch with arrow indicator
b one gang one way pull cord switch
c two way switch with on down d fireman’s switch.
Unit 201
Q1 – D
Q2 – D
Q3 – B
Q4 – D
Q5 – B
Q6 – A
Q7 – D
Q8 – A
Q9 – C
Q10 – B

 

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2.2 Unit 202 Principles of electrotechnology (Stage 1)
Q1 The Tesla is the unit of
a magnetic flux
b molecular flux
c magnetic flux density
d molecular flux density.
Q2 A single rotation of an alternator, intended to provide a 50 Hz supply frequency, will take
a 2 ms
b 20 ms
c 50 ms
d 5000 ms.
Q3 An increase in current through a conductor will lead to
a a decrease in conductor temperature
b a decrease in conductor resistance
c an increase in insulation resistance
d an increase in conductor temperature.
Q4 Four resistors having values of 2 Ω, 2 Ω, 5 Ω and 20 Ω are connected in a parallel circuit arrangement. The total resistance of this circuit is
a 0.8 Ω
b 1.25 Ω
c 29 Ω
d 400 Ω.
Q5 Where P = V I. The value V can be determined using
a ) V = I / P
b ) V = P I
c V = P - I
d V = P/I
Q6 A mass of 20 kg is to be raised by a hoist 2 m in 30 seconds. Assuming no losses, the power required to raise this load is
a 13.08 Watts
b 196.2 Watts
c 392.4 Watts
d 1200 Watts.
Q7 The white or grey pvc outer layer of a twin and cpc flat thermoplastic (pvc) cable is the
a conductor
b insulation
c conductor
d sheath.
Q8 The purpose of a bonding conductor is to provide
a an earth fault path
b an equal potential zone
c short circuit protection
d overload protection.
Q9 A 110 V, centre tapped earth, reduced low voltage supply for power tools provides a voltage of
a 25 V between live conductors
b 55 V to earth
c 110 V to earth
d 12 V SELV.
Q10 A particular extension lead used on a construction site is coloured yellow to
a indicate its mechanical stress properties
b enable it to be seen in the dark
c indicate the supply voltage to it d enable it to be to be identified as suitable for site use.
Unit 202
Q1 – C
Q2 – B
Q3 – D
Q4 – A
Q5 – D
Q6 – A
Q7 – D
Q8 – B
Q9 – B
Q10 – C

 

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Q / Basic protection offers protection against :- A / Direct contact with live parts ,
Q / Fault protection offers protection against :- A / protection against electric shock under fault conditions due to indirect contact ,
Q / A single phase-socket outlet ring circuit supply would have :- A / Four live conductors ,
Q / The abbreviation PV stands for :- A / Photo Voltaic ,
Q / A system with a combined natural and earth within both the supply arrangement and installation is known as a :- A / TN-C : Regs p/30 / 32
Q / A system with a separate neutral and earth within the supply arrangement is know as :- A / TN-S : Regs p/30 / 33
Q / A system with a combined natural and earth within the supply arrangement and separate and earth within the installation is know as :- A / TN-C-S ,
Q / A system whose return path is via earth electrodes is known as a :- A / TT system ,
Q / A voltage band 1 covers :- A / Extra low , voltage , Regs p/31
Q / A voltage band 11 covers :- A / low voltage , Regs p/31
Q / The abbreviation cpc stands for :- A / Circuit protective conductor ,
Q / Class 1 equipment would be :- A / Exposed metalwork earthed ,
Q / Class 11 equipment would be :- A / No earth arrangement ,
Q / The abbreviation SELV stands for :- A / Separated extra low voltage ,
Q / Class 111 equipment would have :- A / An SELV supply , regs p/21

 

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Test Procedures for Electrical Installations :-
( Continuity and Insulation Résistance )

Sequence of Tests ( 612 )
* Continuity of Protective Conductors ( including main and supplementary bonding ). 612.2.1.

* Continuity of Ring Final Conductors. 612.2.2

* Insulation Résistance Tests. 612.3.

* Protection by SELV, PELV or electrical separation. 612.4.

* Basic Protection by barrier or an enclosure provided during erection. 612.4.5.

* Insulation resistance/impedance of floors and walls. 612.5

* Polarity. 612.6

* Earth electrode resistance. 612.7

* Earth loop impedance. 612.9

* Prospective fault current. 612.11

* Check of Phase sequence (for multiphase systems). 612.12

* Functional tests. 612.8, 612.10 and 612.13

ALL TESTS UP TO AND INCLUDING POLARITY are carried out with the ‘mains’ ISOLATED, Earth electrode resistance (if conducted with a Loop Tester) and subsequent tests are carried out with the ‘mains’ ON. If earth electrode resistance is measured using dedicated tester – this is a ‘dead’ test – so ISOLATE. Functional tests also relate to RCD testing.

Continuity of Earth ,
* There are TWO methods available – (R1+R2) or (R2).

* (R1+R2) is often the easier test to carry out for ‘normal circuits’.

* (R2) is used for Bonding conductor tests.


* POINTS TO NOTE:

* Null test leads first – why?

* The test instrument will have a voltage supply of between 4 – 24v (ac or dc) and test current of at least 200mA – why?


1 ) To deduct the resistance of the test leads (and long trailing test lead if used) from the results, when conducting circuit resistance tests.

2 ) This applies electrical ‘pressure’ to the circuit under test – this will identify whether a poor ‘loose’ or ‘dirty’ connection exists. Normal ‘multimeter type’ resistance meters do not apply adequate electrical ‘ pressure’ during a test, so poor connections can go unnoticed!!

( R1 + R2 ) Test
Mains OFF – Temporary Link between Line and CPC in the Consumer Unit ,
Operate ALL Switches , between Line ( Switched ) and CPC at ALL points ( Including Switches ) ↔ ( R1 + R2 ) Test can be Used to Confirm Polarity ,
Note: TEMPORARY LINK IN CONSUMER UNIT CAN BE MADE WITHOUT REMOVING THE CONDUCTORS FROM THEIR TERMINALS.

disconnected here for clarity.Simply connect temporary ‘shorting lead’ between circuit breaker ‘busbar rail’ and CPC block. Then turn on MCB for circuit under test. Measure between any switched live and CPC at end of the circuit under test. Repeat for other circuits. REMEMBER to operate switches to PROVE polarity during test.

Continuity of the Bonding Conductors
Avoid Parallel Paths ◄► Test Each bonding Conductors in Turn , Remember the Disconnected it from the MET ( Main Earthing Terminal )before Testing and Re-Connecting it after Testing

Main Switch in Consumers Unit is OFF , all MCBs OFF , Remember – the Main Earthing Conductor is Removed for this Test , Remember to Reconnect IT Afterwards ,
* Main Earthing Conductor → : Main Earthing Terminal → ( MET ) Gas Meter / 600mm < ( Test Lead on Copper Pipe Water → : Other Lead on Main Earthing Terminal → ( MET ) 0.01Ω

R2 ) test shown here. REMEMBER to NULL test leads due to relatively low values of BONDING conductor resistance being adversely affected if resistance of test leads was added to final readings inadvertently. Record the measured equipotential bonding conductor reading onto the Schedule of Test Results sheet.

Ring Circuit , ( R1 + R2 )
Mains OFF – Shower “ Pull/Cord “ Switch ON .
Shower itself Switched OFF .
Test between Line and CPC . ( R1 + R2 ) Test at Ends of Shower “ Radial Circuit ◄
Operate Pull-Cord to Confirm Polarity !!!!!
Line and CPC “ Temporally Linked “ in Consumer Unit
( One Lead on Con/ Block in Shower Brown ◄► Other Lead on Con/ Block in Shower CPC ) 0.21Ω

 

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Continuity of Earth ( Including Bonding Conductor s )

* (R1+R2) or (R2) readings will be dependent on LENGTH and CSA of Live and Earth (or just earth) conductor(s) used .

* Tables in ‘On-site guide’ give comparative values.

* Measured (R1+R2) or (R2) impedance values MUST be LOW ohms readings.

* Bonding conductors MUST be 0.05 ohms or less.

* These readings are recorded on ‘Schedule of test results form’.

* (R1+R2) test can also be used to check POLARITY (so is a preferred test here)


Completing the Test Results Sheet : ( this is just to give you an idea when you go onto : Schedule of Test Results ) Testing

Schedule of Test Results ,
Method of Fault Protection ( Automatic Disconnection of Supply )
Equipment Vulnerable to Testing !! Timer in Bathroom Fan ◄◄
Description of Work !! Periodic Inspection and Test
Circuit Description :-
Overcurrent Device / Short-Circuit Capacity 6 kA ◄
Shower : Type MCB ( B ) : Rating 40 Amp : Wiring Conductors 6mm2 ◄►Wiring Conductors 2.5mm2 ( Continuity – R1 + R2 / 0.21Ω
Remember Polarity ◄
Ring Circuit : Type MCB ( B ) : Rating 32 Amp : Wiring Conductors 2.5mm2 ◄►Wiring Conductors 1.5mm2 ( Continuity – R1 + R2 / !!!!! Ω
Garage : Type MCB ( B ) : Rating 32 Amp : Wiring Conductors 4.0mm2 ◄►Wiring Conductors 2.5mm2 ( Continuity – R1 + R2 / !!!!! Ω
Lights : Type MCB ( B ) : Rating 6 Amp : Wiring Conductors 1.5mm2 ◄►Wiring Conductors 1.0mm2 ( Continuity – R1 + R2 / !!!!! Ω
Gas Bonding ( Equipotential ) Wiring Conductors : 10mm2 ( Continuity – R2 0.01Ω

Continuity of Ring Final Conductors
* This is the ‘trickiest’ of the ‘dead-tests’ that electricians often find difficult to understand.

* The test has TWO purposes.

* 1) To check that the circuit is in a RING configuration (end-to-end).

* 2) To check that NO interconnects exist within the ‘RING’ which could give rise to danger.

* The tests are carried out in THREE stages….


Continuity of Ring Final Conductors Stage 1 – End / to / End Readings ,
Measure Continuity of each pair of Live,s – Neutral,s and CPC,s this will Confirm a Ring Circuit . Live and Neutrals should have same readings
Cpc,s will be approx 1.67x Greater .

Measure open end live-to-live and make a note of reading, do same for neutrals and CPC ’s. These readings are your basis for calculating EXPECTED VALUES for subsequent tests on the RING CIRCUIT.

Continuity of Ring Final Conductors Stage 2 – Line and Neutral Readings ,
Ensure Socket Under Test is Switched ON ! Lines and Neutrals ( Crossed-Linked in Consumer Unit )

All Sockets Outlets will have very similar Readings if Connected on a “ Ring Circuit “
Test between Line / Neutral at Each Socket Outlet ( Note Earth Test Lead is Used for this Test )
( PS you are looking for : Equal Readings from Sockets Outlets !!

A 1.5 MM SQ CPC WILL HAVE APPROX. 1.67X MORE RESISTANCE THAN A 2.5 MMSQ LIVE CONDUCTOR OF THE SAME LENGTH, hence the CPC-CPC reading being 0.55 ohms (1.67x the 0.33 ohms for the live conductor end-to-end reading).
When ring conductors are cross linked as shown (Live – neutral and Neutral – live cross-linking) TOTAL resistance reading is 0.165 ohms. This is R1 (live end-to-end) + RN (neutral-to-neutral)/4 OR, as both Live and Neutral end-to-end readings were identical, EITHER one divided by 2 (i.e. 0.33/2 = 0.165 ohms). This IS THE EXPECTED READING AT EACH SOCKET OUTLET ON THE RING. A substantially different reading may indicate that ‘that’ outlet is a spur (or interconnect) and should be investigated further. Values from this test are NOT recorded on the Schedule of Test Results – but only used as a reference to each socket.

Continuity of Ring Final Conductors Stage 3 – Line and CPC Readings
( R1 + R2 ) Test Ensure Sock Outlet Under Test is Switched ON !
Lives and CPCs are “ Cross-Linked “ in Consumer Unit
All Socket Outlets will have Very Similar Readings if Connected on a “ Ring Circuit “
( PS you are looking for : Equal Readings from Sockets Outlets !!

If live-to-live open end readings = 0.33 ohms and CPC-to-CPC open end readings = 0.55 ohms, then when cross linked as shown reading should be 0.22 ohms at position shown and each socket outlet on the ring. This is the EXPECTED READING AT EACH SOCKET OUTLET ON THE RING. A substantially different reading may indicate that ‘that’ outlet is a spur (or interconnect) and should be investigated further.

0.33 (R1) + 0.55 ( R2) /4 = approx. 0.22 ohms.
R2 value is 0.53 / 2 = approx. 0.27 ohms.
Record EITHER value onto the Schedule of Test Results.

 

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“ Interconnection’s” and “ Spurs” on a Ring Circuit ,
( R1 + R2 ) Test Ensure Socket Outlets under Test is Switched ON !
Lives and CPCs are Crossed – Linked in Consumer Unit ,

Test between Live and CPC at Socket Outlets ( Note Neutral Test Lead is Unused for this Test .
► these Two Sockets are “ Spurred “ from the “ Ring “ Circuit – so Reading is “ Substantially “ Different from expected Ring Value ,
Not :- Equal Readings , 0.22Ω / 0.52Ω

As shown here, a substantially different reading is obtained at an outlet. Here, if the last ‘good’ (i.e. 0.22 ohm reading) socket front were to be removed for closer inspection, THREE 2.5mmsq conductors would be seen. Subsequent sockets with increasing resistance values are the indication of an ‘illegal’ spur.

Continuity of Ring Final Conductors Re-Cap :-

* Measure between EACH end of PHASE, NEUTRAL and CPC conductors (note; phase and neutral should be the same reading, cpc may be slightly higher if its CSA is smaller). Record the results.

* Cross-link PHASES and NEUTRALS and measure the resistance at EACH outlet. Total resistance should be (R1+Rn)/4. Check for the same reading at EACH socket outlet on the ring circuit.

* Cross-link PHASES and CPC’s and measure the resistance. Total resistance should be (R1+R2)/4. Check for the same reading at EACH socket outlet on the ring circuit.

* Any SUBSTANTIALLY different readings and any outlet is an indication of an SPUR or INTERCONNECT at that outlet – investigate further.

RECORD the (R1+R2) measured value onto the Schedule of Test Results sheet.

 

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Typical BS-1362 :- 3A Cartridge fuse in a BS-1363 plug connected to Class 1 Equipment , ( just to show you two different BS-No 1362 / 1363

BS-1362 Cartridge Fuse have a Rated Voltage of 240V and are suitable for use in Circuits’ where the A.C. system Voltage does Not Exceed 110%
Of that Voltage ( that is 264V )
The Rated Frequency of BS-1362 Cartridge Fuse is 50Hz , however the Standard Conditions of Service for such Fuses permit their Use in Circuits having a Frequency within the Range 45 to 62Hz ,

The Rated Current ( In ) allocated by the Manufacturer may be any Value up to and including 13A , although the Values preferred by BS-1362 are 3A and 13A , Other Values of Rated Current Used for BS-1362 Cartridge Fuses are 2A / 5A / and 10A .
Cartridge Fuses Complying with BS-1362 are Required to be Colour Coded According to their Rated Current , and be Marked with their Rated Current Value ,

The Rated Current of BS-1362 Cartridge Fuse is Applicable to Specific Ambient Temperature Conditions . if it is Intended to Use a BS-1362 Fuse where the Ambient Temperature Conditions Differ from the Service Conditions of BS-1362, the Manufacturer should be Consulted Prior to such Use .

Where a Fuse is Used to Provide Fault Current Protection Only , for Example to protect an Appliance with Integral Overload Protection , the Fault Clearance Time Under both Short-Circuit and Earth-Fault Conditions has to meet the Requirements of Regulation 434.5.2 .

For Overload Current Protection , the Rated Current of a Fuse is to be Selected to meet the Requirements of Section 433 of BS-7671 .

Where Overload Current Protection is Afforded by a BS-1362 Cartridge Fuse , there tends to be a need for the Circuit-Conductors to be of a Larger Cross-Sectional Area than Required by most Other Types of Overcurrent Protective Device Used . this is because of the need to Comply with Condition ( iii ) of Regulation 433.1.1 . which Requires that ( I2 ) the Current Causing Effective Operation of the Protective Device , does Not Exceed 1.45 times the Lowest of the Current-Carrying Capacities ( Iz ) of any of the Conductors of the Circuit ,

BS-1362 Cartridge Fuses are Required to be Indelibly Marked with the Following Information .
* Manufacturers Name or Identifying Mark .
* British Standard Number BS-1362 .
* Rated Current in Amperes .

 

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Cartridge Fuse to BS-1362 :-
Cartridge Fuses Conforming to BS-1362 are for Use in Low-Voltage Single-Phase A.C circuits of Nominal Frequency 50 or 60Hz .they are General-Purpose Fuses intended for Domestic and Similar Purposes , Primarily in Plugs Complying with BS-1363 although Not Exclusively so , BS-1362 Cartridge Fuses are , for Example Commonly Used in Fused Connection Units .

Where it is intended to Use a BS-1362 Cartridge Fuse in a D.C. circuit , the Fuse Manufacturer should be Consulted prior to its Use .
The Rated Values and Characteristics given in BS-1362 are Applicable to Alternating Current ( A.C. ) the Suitability of BS-1362 Fuses for D.C. Applications Needs to be Established , and the Rated Values and Characteristics Obtained for such Applications .

 

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Assessment Questions : ( Some Old Notes to play around with ) some are still Active with -&-s ,
2) The main reason for incorporating the wiring Regulations into British Standards BS-7671 was to harmonistion with European Standards , ( True ) *
3) A cable sheath earth supply or TN-S System of supply is one of the most common types of underground supply in the UK ( True ) *
4) A Delivery Note : is a standard form completed by most electrical trainees to inform an employer of how much time has been spent working on a particular job ( False )
5) When materials are delivered to site , the person receiving the goods is required to sign the drivers Time-Sheet to prove that the supplier has delivered the goods as requested ( False ) *
6) A radial socket circuit is wired from the source of supply to each socket in turn and the last socket is wired back to the source of supply ( False )
8) Industrial installations use robust cable enclosures such as conduits and trunking , A conduit is a square or rectangular section from mild steel plate , A trunking is a tube , or pipe in which insulated conductors are contained , ( False ) *
9) Individual cables or accessories may be fixed directly to a surface with a suitable nail , screw or bolt , A spring toggle bolt provides a good method of fixing to concrete or masonry , a Rawbolt provides a good method of fixing to hollow partition walls ( False )
10) The “ Waste Regulations “ tell us that we have a “ Duty of Care “ to handle , recover and dispose of waste responsibly , you company is responsible for the waste that it produces , so always make sure that waste material is put into the proper skip and taken away only by “ Authorised “ companies ( True ) *

Multiple Choice Assessment Questions :-
Tick the correct answer , NOTE that more than ONE answer may be correct ,

11) The Electricity at Work Regulations are :
a) Non-Statutory Regulations ,
b) Statutory Regulations ◄
c) a Code of Practice ,
d) a British Standard ,
12) The IEE Regulations are :
a) Non-Statutory Regulations , ◄
b) Statutory Regulations ,
c) a Code of Practice , ◄
d) a British Standard , ◄
13) A British Standard having a BS number is a :
a) Statutory Regulations ,
b) Non-Statutory Regulations ,
c) British compliant Standard , ◄
d) European harmonised Standard ,
14) A British Standard having a BS-EN number is a :
a) Statutory Regulations ,
b) Non-Statutory Regulations ,
c) British compliant Standard ,
d) European harmonised Standard , ◄
15) part 5 of the IEE Regulations deals with :
a) Protection for Safety ,
b) Selection and Erection of Equipment , ◄
c) Special Installations ,
d) Inspection and Testing ,
16) Part 6 of the of the IEE Regulations deals with :
a) Protection for Safety ,
b) Selection and Erection of Equipment ,
c) Special Installations ,
d) Inspection and Testing , ◄
17) A scale drawing showing the position of equipment by graphical symbols is a description of a :
a) Block diagram ,
b) Wiring diagram ,
c) Circuit diagram ,
d) Layout diagram or site plan , ◄
18) A diagram which shows the detailed connections between individual items of equipment is a description of a :
a) Block diagram ,
b) Wiring diagram , ◄
c) Circuit diagram ,
d) Layout diagram or site plan ,
19) A diagram which shows very clearly how a circuit works , where all components are represented by a graphical symbol is a description of a :
a) Block diagram ,
b) Wiring diagram ,
c) Circuit diagram , ◄
d) Layout diagram or site plan ,
20) A Time Sheet show’s :
a) a Record of goods delivered by a supplier ,
b) a Record of work done which is outside the original contact ,
c) Information about work to be done usually a small job ,
d) the actual time spent working on a particular job or site , ◄

 

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21) A job Sheet or Job Card shows :
a) a record of goods delivered by a supplier ,
b) a record of work done which is outside the original contact ,
c) information about work to be done , usually a small job , ◄
d) the actual time spent working on a particular job or site ,
22) A Day Work Sheet shows :
a) a record of goods delivered by a supplier ,
b) a record of work done which is outside the original contract , ◄
c) information about work to be done, usually a small job ,
d) the actual time spent working on a particular job or site ,
23) A Delivery Note shows :
a) a Record of goods delivered by a supplier , ◄
b) a Record of work done which is outside the original contract ,
c) Information about work to be done , usually a small job ;
d) the actual time spent working on a particular job or site ,
24) A cable sheath earth supply is also called a :
a) TN-S system , ◄ ( Regs p/32 /33/34 )
b) TN-C-S system ,
c) TT system ,
d) Standby System ,
25 ) A PME supply is also called a :
a) TN-S system ,
b) TN-C-S system , ◄ ( Regs p/32 /33/34 )
c) TT system ,
d) Standby System ,
26) a No earth provided supply is also called a :
a) TN-S system ,
b) TN-C-S system ,
c) TT system , ◄ ( Regs p/32 /33/34 )
d) Standby System ,
27) The electricity supply to a domestic consumer is usually protected at the incoming service position by a :
a) Meter ,
b) Double pole switch ,
c) 100A MCB ,
d) 100A HBC fuse , ◄
28) The assumed current demand for each lighting point in a domestic installation should be based upon the equivalent of :
a) 5 amps per lampholder ,
b) 6 amps per lampholder ,
c) 100 watt per lampholder , ◄
d) 3kW per lampholder ,
29 The protective Type B MCB for lighting circuit fed from a consumer unit in 1.0mm2 or 1.5mm2 cable should be rated at :
a) 6A or 10A , ◄
b) 10A or 16A ,
c) 16A or 32A ,
d) 32A or 40A ,
30) The protective Type B MCB for Ring circuit fed from a consumer unit in 2.5mm2 cable should be rated at :
a) 6A or 10A ,
b) 10A or 16A ,
c) 16A or 32A ,
d) 32A only , ◄
31) Each ring circuit of 13A sockets must cover a floor area of no more than :
a) 50m2 ,
b) 75m2 ,
c) 100m2 , ◄ ( O.S.G. p/158 )
d) unlimited ,
32) A radial circuit of 13A sockets wired in 2.5mm2 / 1.5mm2 PVC cable must cover a floor area of no more than :
a) 50m2 , ◄ ( O.S.G. p/158 )
b) 75m2 ,
c) 100m2 ,
d) unlimited ,
33) A radial circuit of 13A sockets wired in 4.0mm2 / 2.5mm2 PVC must cover a floor area of no more than :
a) 50m2 ,
b) 75m2 , ◄ ( O.S.G. p/158 )
c) 100m2 ,
d) unlimited ,
34) an MI cable is especially suited to :
a) domestic installations ,
b) fire alarm installations , ◄
c) burying underground ,
d) industrial installations , ◄

 

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35) a PVC/SWA cable is especially suited to :
a) domestic installations ,
b) fire alarm installations ,
c) burying underground , ◄
d) industrial installations ,
36) a PVC Insulated and sheathed cable is especially suited to :
a) domestic installations , ◄
b) fire alarm installations ,
c) burying underground ,
d) industrial installations ,
37) FP 200 cables are especially suited to :
a) domestic installations ,
b) fire alarm installations , ◄ ( can be used for Emergency Lighting )
c) burying underground ,
d) industrial installations ,
38) A steel conduit installation is especially suited to :
a) domestic installations ,
b) fire alarm installations ,
c) burying underground ,
d) industrial installations , ◄
39) A metal trunking installation is especially suited to :
a) domestic installations ,
b) fire alarm installations ,
c) burying underground ,
d) industrial installations , ◄
40) Cable tray installations are especially suited to :
a) domestic installations ,
b) fire alarm installations , ◄
c) burying underground ,
d) industrial installations , ◄
41) bathroom installations receive special consideration in the IEE Regulations :
a) electricity and flammable liquids ,
b) electricity and water , ◄
c) the presence of corrosive substances ,
d) the potential for mechanical damage ,
42) Construction sites receive special consideration in the IEE Regulations :
a) electricity and flammable liquids ,
b) electricity and water , ◄
c) exposure to wind and rain , ◄
d) presence of livestock and vermin ,
43) Agricultural installations receive consideration in the IEE Regulations because of the hazard associated with :
a) electricity and water , ◄
b) presence of livestock and vermin , ◄
c) potential for mechanical damage , ◄
d) electricity and flammable liquids ,
44) Petrol pump installations receive special consideration from may Statutory Regulations because of the hazard associated with :
a) electricity and water ,
b) electricity and flammable liquids , ◄
c) exposure to wind and rain ,
d) the temporary nature of the supply
45) Locations containing a bath or shower are divided into zones or separate areas . the most dangerous zone is classified as :
a) Zone 0 , ◄
b) Zone 1 ,
c) Zone 2 ,
d) Zone 10 ,
46) The permissible colours of 230V Single-Phase wiring , up to 30th march 2006 was :
a) brown , blue , green/yellow ,
b) brown , black , gray ,
c) red , black , green/yellow , ◄ ( you’ll never get this )
d) red , yellow , green /yellow ,
48) PVC insulated and sheathed cables are very likely to be fixed and supported by :
a) wood screws and plastic plugs ,
b) a PVC clip and hardened nail , ◄
c) an expansion bolt ,
d) a clip on girder fixing ,
49) A lightweight piece of electrical equipment is very likely to be fixed to a plasterboard by :
a) wood screws and plastic plugs ,
b) a PVC clip and hardened nail ,
c) an expansion bolt ,
d) a spring toggle bolt , ◄

 

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50) a heavy electric motor is very likely to be fixed to a concrete floor by :
a) wood screws and plastic plugs ,
b) a clip on girder fixing ,
c) an expansion bolt , ◄
d) a spring toggle bolt ,
51) A run of trunking suspended in an industrial installation is very likely to be fixed to the main structure of the building by :
a) wood screws and plastic plugs ,
b) a clip on girder fixing , ◄
c) an expansion bolt ,
d) a spring toggle bolt ,
52) A run of cable tray suspended in a modern Supermarket building is very likely to be attached to the main structure of the :
a) wood screws and plastic plugs ,
b) a clip on girder fixing , ◄
c) an expansion bolt ,
d) a spring toggle bolt ,
53) what action is necessary to produce a “ secure electrical isolation “ :
a) isolate the supply and observe that the voltage indicator reads zero ,
b) First connect a test device such as a voltage indicator to the supply ,
c) Larger pieces of equipment may require isolating at a local isolator switch ,
d) The isolated supply must be locked off or secured with a small padlock , ◄
54) A voltage proving unit :
a) is used for transmitting data along optical fibre cables ,
b) provides a secure computer supply ,
c) shows a voltage indicator to be working correctly , ◄
d) tests for the presence of a mains voltage supply ,
55) for working even a short distance above ground level periods , the safest piece of access equipment would be :
a) a stepladder ,
b) a platform tower , ◄
c) an extension ladder ,
d) a hard hat ,
56) an example of “ special waste : is :
a) sheets of asbestos , ◄
b) old fibre-glass roof insulation ,
c) old fluorescent tubes , ◄
d) part coils of PVC insulated cables ,
57) Special Waste must be disposed of :
a) in the general site skips ,
b) in the general site skips by someone , designated to have a “ Duty of Care “
c) at the “ Household Waste “ re-cycling centre ,
d) by an “ Authorised Company “ using a system of waste transfer notes , ◄
58) the Heath & Safety at Work Act places the responsibility at work on :
a) the Employer ,
b) the Employee ,
c) both the Employer and Employee ,
d) the Main Contactor ,
59) Under the Heath & Safety at Work Act an Employer must ensure that :
a) the working conditions are appropriate and safety equipment is provided , ◄
b) Employees take reasonable care of themselves and others as a result of work activities ,
c) employees co-operate with an employer and do not interfere with or misuse safety equipment ,
d) that plant and equipment is properly maintained , ◄
60) Under the Heath & Safety at Work Act Employees must ensure that :
a) the working conditions are appropriate and safety equipment is provided ,
b) they take reasonable care of themselves and others as a result of work activities , ◄
c) they co-operate with an Employer and do not interfere with or misuse safety equipment , ◄
d) plant and equipment is properly maintained ,

 

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Proving Unit :-

Switch ON ,
Insert probe ends of Testing Device into A.C./D.C. Outlet Sockets and while holding Testing device apply a light pressure in direction of Sockets ,
Switch OFF ,
Withdrawal of Testing Device instantly De-Energises ( form the Proving Unit )
Proof Testing ,
With Probes of Testing Device Inserted into Sockets APPLY SUFICIENT PRESURE for Good Electrical Contact ,
CHECK ∆ INDICATES AT ALL TIMES During Testing , Replace Battery if , in Normal Use , it Does NOT Iluminate , ◄

Check ALL NEON LAMPS Located within the Testing Device Iluminate for Duration of PROOF TESTING ,◄

( Remember that -&-s will ask about : Read Instructions Before Use/Operating )

 

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Proving Unit :-

To Deter ANYONE from RECNNECTING the Supply , a NOTICE must be FIXED on the Isolating SAYING “ Danger – Electrician at Work
Which you should Practice in the Workshop Under the Guidance of your Tutor or at Work Under the Guidance of your Supervisor , Electrical Isolation is an Important Safety Procedure ,

Select an Approved Test lamp or Voltage Indicating device , ▼
Verify that the Device is Functioning Correctly on a Known Supply or Proving Unit , ▼
▼ Satisfactory ? →→ No ► ( Replace or Repair )
Yes :
Locate and Identify Circuit or Equipment to be Worked Upon
Is the Circuit or Equipment in Service ? →→ No ►( Establish where and why it was De Energised )
Yes :
Identify Means of Isolation ▼
Ensure Isolation of the Circuit or Equipment by ▼
- Switching Off .
- Withdrawing Fuses .
- Locking off Isolating Switches or MCBs , ▼
Verify that the Circuit or Equipment to be Worked Upon is DEAD Using a Voltage Indicating Device Testing between :- ▼
Line / and Earth ,
Line / and Neutral ,
Neutral and Earth , ▼
Yes :
Satisfactory ? →→ DEAD ► Fit WARNING Signs , Recheck that the Voltage Indicating Device is Functioning Correctly on a Know Supply or Proving Unit , ▼
▼ Satisfactory ? Yes ( Begin Work ) No ► Replace or Repair and go Through the Procedure Again :
LIVE ~ ~ ~
Discover why with CARE and go Though the Procedure Again ,

 

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Circuit Diagram :
A Circuit Diagram shows most Cleary how a Circuit Works, All the Essential Parts and Connections are Rep-resented by their Graphical Symbols . The Purpose of a Circuit Diagram is to Help our Understanding of the Circuit , it will be Laid Out as Clearly as Possible , without regards to Physical Layout of the Actual Components and , Therefore , it may Not Indicate the most Convenient way to Wire-a-Circuit ,

Symbols and Multiples for Use with SI Units :
Prefix : Mega , Symbol : M , Multiplication Factor : x 10/6 or x 1000000 ,
Prefix : Kilo , Symbol : k , Multiplication Factor : x 10/3 or x 1000 ,
Prefix : Hecto , Symbol : h , Multiplication Factor : x 10/3 or 100 ,
Prefix : Decca , Symbol : da , Multiplication Factor : x 10 or x 10 ,
Prefix : Deci , Symbol : d , Multiplication Factor : x 10_1 or ÷ 10 ,
Prefix : Centi , c , Multiplication Factor : x 10_2 or ÷ 100 ,
Prefix : Milli , m , Multiplication Factor : x 10_3 or ÷ 1000 ,
Prefix : Micro , m , Multiplication Factor : x 10_6 or ÷ 1000000 ,

An Electric Fan-Heater was found to Take 10A when Connected to the 230V Mains Supply , Calculate the Résistance of the Heater Element :- ??
From ( R ) = V/I ( Ω ) ◄► ( R = 230 ÷ 10A = 23Ω ) The Heater Element Résistance is 23Ω

Calculate the Current Flowing in a Disco “ Sound and Light “ Unit having a Résistance of ( 57.5Ω ) when it is Connected to the 230V Electrical Mains ,
From ( I ) = V/R ( A ) ◄► ( I = 230V ÷ 57.5Ω = 4A ( The “ Sound and Light “ Unit takes 4 Amps ,

Resistivity :
“ Remember “ ► The Résistance or Opposition to Current Flow Varies , Depending Upon the Type of Material being Used to Carry the Electric Current ,

Using these Values we can Calculate the Résistance of Different Materials Using the Formulae !!!
Résistance ( R ) = pL / a ( Ω )
Where ( p ) ( the Greek Letter rho ) is the Resistivity Value for the Mater , ( l ) is the Length and ( a ) is the Cross-Sectional Area ,
( just for talk sake ) Copper : Resistivity ( Ωm ) 17.5 x 10-9
( just for talk sake ) Aluminum : Resistivity ( Ωm ) 28.5 x 10-9

* Calculate the Résistance of 100m of 2.5mm2 Copper Cable Using the Resistivity Values ,
We know that ( R ) = pL / a . Ω
Therefore ( R ) = 17.5 x 10-9 x 100 ……. 2.5 x 10-6
Therefore R = 700 x 10-3 ( Ω ) or
R = 700 ( mΩ )

Note : the Cross-Section of the Cable is in mm2 ( mm = 10-3 so, ) mm x mm = 10-6
* Calculate the Résistance of 100m of 2.5mm2 Aluminum Cable Using the Resistivity Values ,
We know that ( R ) = pL / a . Ω
Therefore ( R ) 28.5 x 10-9 x 100 ……. 2.5 x 10-6
Therefore R = 1140 x 10-3 ( Ω ) or
R = 1140 ( mΩ )

 

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So , if -&- Ask you about :-
Syllabus : Consider Weight , Mass , Force and Work done by a Force so let us Define some of these Scientific Term ,
Mass : this is a Measure of the Amount of Material in a Substance such as Wood or Metal ,
Weight : this is a Measure of Force which the Mass Exerts , it Exerts this Force because it is being Attracted towards the Earth by Gravity ,
Force : The Presence of a Force can Only be Detected by its Effect on an Object , A Force may Cause a Stationary Object to Move or a Moving Object to Stop ,
Gravity : The Force of Gravity Acts toward the Centre of the Earth and Causes Objects to Fall to the Ground at a Rate of ( 9.81 m/s )
Work Done : the Work done by Force is a Measure of the Force Exerted Time the Distance Moved in the Direction of the Force ,

Suppose a Broken-Down Car was to be Pushed along a Road ; Work would be Done on the Car by Applying the Force Necessary to Move it Along the Road , Heavy Breathing and Perspiration would be Evidence of Work Done !!!!!!!!!

Work Done = Force x Distance Moved in the Direction of the Force ( J )
The SI Unit of Work Done is the Newton Metre or Joule ( Symbol J )
Example ;
A Building Hoist Lift ten 50kg bags of Cement through a Vertical Distance of 30m to the Top of a High Rise Building , Calculate the Work Done by the Hoist , Assuming the Acceleration due to Gravity to be 9.81 m/s-2 ,
Work done = Force x Distance moved ( J )
But, Force = Mass x Acceleration ( N )
Therefore : Work done = Mass x Acceleration
x Distance Moved ( J )

work done = 10 x 50kg x 9.81m/s-2 x 30m
work done = 147.15kJ ,