Advanced Electrical Installation Work 2365 Edition. City and Guilds Edition

Trevor Linsley

Chapter 6 Electrical systems design - all with Video Answers

Educators

Chapter Questions

Problem 1

'The conductive mass of the earth' is one definition of:
a. earth
b. earthing
c. bonding conductor
d. circuit protective conductor.

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Problem 2

A protective conductor connecting exposed conductive parts of equipment to the main earthing terminal is one definition of:
a. earth
b. earthing
c. bonding conductor
d. circuit protective conductor.

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Problem 3

A protective conductor connecting exposed and extraneous parts together is one definition of:
a. earth
b. earthing
c. bonding conductor
d. circuit protective conductor.

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Problem 4

The act of connecting the exposed conductive parts of the installation to the main earthing terminal is called:
a. earth
b. earthing
c. bonding conductor
d. circuit protective conductor.

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Problem 5

The act of linking together the exposed and extraneous metal parts is called:
a. earthing
b. bonding
c. basic protection
d. fault protection.

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Problem 6

The protection provided by insulating live parts is called:
a. extraneous conductive parts
b. basic protection
c. exposed conductive parts
d. fault protection.

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Problem 7

A current which exceeds the rated value in an otherwise healthy circuit is one definition of:
a. earthing
b. bonding
c. overload
d. short-circuit.

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Problem 8

An overcurrent resulting from a fault of negligible impedance is one definition of:
a. earthing
b. bonding
c. overload
d. short-circuit.

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The linking together of the exposed or extraneous conductive parts of an installation for the purpose of safety is one definition of:
a. earthing
b. protective bonding
c. exposed conductive parts
d. extraneous conductive parts.

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Problem 10

The conduit and trunking parts of the electrical installation are:
a. earth conductors
b. bonding conductors
c. exposed conductive parts
d. extraneous conductive parts.

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Problem 11

The gas, water and central heating pipes of the building not forming a part of the electrical installation are called:
a. earthing conductors
b. bonding conductors
c. exposed conductive parts
d. extraneous conductive parts.

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Problem 12

The protection provided by insulating the live parts of the electrical installation is called:
a. overload protection
b. short-circuit protection
c. basic protection
d. fault protection.

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Problem 13

The protection provided by protective bonding and automatic disconnection of the supply is called:
a. overload protection
b. short-circuit protection
c. basic protection
d. fault protection.

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Problem 14

The metalwork of the electrical installation is called:
a. extraneous conductive parts
b. basic protection
c. exposed conductive parts
d. fault protection.

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Problem 15

The metalwork of the building and other service pipes is called:
a. extraneous conductive parts
b. basic protection
c. exposed conductive parts
d. fault protection.

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Problem 16

The protection provided by protective bonding and automatic disconnection of the supply is called:
a. extraneous conductive parts
b. basic protection
c. exposed conductive parts
d. fault protection.

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Problem 17

Cutting off the electrical supply in order to ensure the safety of those working on the equipment is one definition of:
a. basic protection
b. fault protection
c. protective bonding
d. isolation switching.

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Problem 18

A current which exceeds the rated current in an otherwise healthy circuit is one definition of:
a. fault protection
b. an overcurrent
c. an overload current
d. a short-circuit current.

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Problem 19

The weakest link in the circuit designed to melt when an overcurrent flows is one definition of:
a. fault protection
b. a circuit protective conductor
c. a fuse
d. a consumer unit.

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Problem 20

According to IET Regulation 411.3.2.2 all final circuits not exceeding $32 \mathrm{~A}$ in a building supplied with a $230 \mathrm{~V}$ TN supply shall have a maximum disconnection time not exceeding:
a. $0.2 \mathrm{~s}$
b. $0.4 \mathrm{~s}$
c. $5.0 \mathrm{~s}$
d. unlimited.

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Problem 21

To ensure the effective operation of the overcurrent protective devices, the earth fault loop path must have:
a. a $230 \mathrm{~V}$ supply
b. a very low resistance
c. fuses or MCBs in the live conductor
d. a very high resistance.

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Problem 22

A load connected to the three phases of a star-connected threephase four-wire supply system from the local substation would have a voltage of:
a. $230 \mathrm{~V}$
b. $400 \mathrm{~V}$
c. $25 \mathrm{kV}$
d. $132 \mathrm{kV}$.

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Problem 23

A load connected to phase and neutral of a star-connected three-phase four-wire supply system from the local substation would have a voltage of:
a. $230 \mathrm{~V}$
b. $400 \mathrm{~V}$
c. $25 \mathrm{kV}$
d. $132 \mathrm{kV}$.

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Problem 24

An electrical cable is made up of three parts which are:
a. conduction, convection and radiation
b. conductor, insulation and outer sheath
c. heating, magnetic and chemical
d. conductors and insulators.

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Problem 25

An appropriate wiring method for a domestic installation would be a:
a. metal conduit installation
b. trunking and tray installation
c. PVC cables
d. PVC/SWA cables.

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Problem 26

An appropriate wiring method for an underground feed to a remote building would be a:
a. metal conduit installation
b. trunking and tray installation
c. PVC cables
d. PVC/SWA cables.

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Problem 27

An appropriate wiring method for a high-temperature installation in a boiler house is:
a. metal conduit installation
b. trunking and tray installation
c. FP 200 cables
d. MI cables.

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Problem 28

An appropriate wiring system for a three-phase industrial installation would be:
a. PVC cables
b. PVC conduit
c. one which meets the requirements of Part 2 of the IET Regulations
d. one which meets the requirements of Part 5 of the IET Regulations.

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Problem 29

A standard form completed by every employee to inform the employer of the time spent working on a particular site is called:
a. job sheet
b. time sheet
c. delivery note
d. daywork sheet.

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Problem 30

A record which confirms that materials ordered have been delivered to site is called:
a. job sheet
b. time sheet
c. delivery note
d. daywork sheet.

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Problem 31

A standard form containing information about work to be done usually distributed by a manager to an electrician is called:
a. job sheet
b. time sheet
c. delivery note
d. daywork sheet.

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Problem 32

A standard form which records changes or extra work on a large project is called a:
a. job sheet
b. time sheet
c. delivery note
d. daywork sheet.

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Problem 33

A graph which shows the sequence or time to be taken on various electrical activities within the contract as a whole is called a:
a. network analysis
b. variation order
c. bar chart
d. tender.

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Problem 34

A formal contract to supply goods or carry out work at a stated price is called a:
a. network analysis
b. variation order
c. bar chart
d. tender.

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Problem 35

A record of the work done which is outside or in addition to the original electrical contract is called a:
a. network analysis
b. variation order
c. bar chart
d. tender.

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Problem 36

A method of showing the separate activities or tasks which make up a large or complex electrical contract is called a:
a. network analysis
b. variation order
c. bar chart
d. tender.

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Problem 37

We know that we have a 'duty of care' to dispose responsibly of all waste material which the working environment creates. So what is the 'responsible' way to dispose of the packaging from boxes of electrical equipment and fittings?
a. place it in the general waste skip which will go to landfill
b. place it in the skip designated for recycling materials
c. have it removed by a specialist waste contractor before your electrical work begins
d. recycle through a specialist hazardous waste company.

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Problem 38

We know that we have a 'duty of care' to dispose responsibly of all waste material which the working environment creates. So what is the 'responsible' way to dispose of asbestos material?
a. place it in the general waste skip which will go to landfill
b. place it in the skip designated for recycling materials
c. have it removed by a specialist waste contractor before your electrical work begins
d. recycle through a specialist hazardous waste company.

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Problem 39

We know that we have a 'duty of care' to dispose responsibly of all waste material which the working environment creates. So what is the 'responsible' way to dispose of the offcuts of conduit and trunking and old metal fluorescent fittings?
a. place it in the general waste skip which will go to landfill
b. place it in the skip designated for recycling materials
c. have it removed by a specialist waste contractor before your electrical work begins
d. recycle through a specialist hazardous waste company.

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Problem 40

We know that we have a 'duty of care' to dispose responsibly of all waste material which the working environment creates. So what is the 'responsible' way to dispose of dozens of old fluorescent tubes and SON lamps?
a. place it in the general waste skip which will go to landfill
b. place it in the skip designated for recycling materials
c. have it removed by a specialist waste contractor before your electrical work begins
d. recycle through a specialist hazardous waste company.

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01:59

Problem 41

The current demand of $10-65 \mathrm{~W}$ fluorescent tubes connected to a $230 \mathrm{~V}$ supply is:
a. $283 \mathrm{~mA}$
b. $5.07 \mathrm{~A}$
c. $150 \mathrm{~W}$
d. $650 \mathrm{~W}$.

Aja S

Numerade Educator

01:07

Problem 42

Ten lighting points are to be wired in a domestic $230 \mathrm{~V}$ home. Calculate the assumed current demand of the 10 lighting points which are to be connected to fittings of unknown style or rating at a later date.
a. $\quad 43.5 \mathrm{~mA}$
b. $\quad 4.35 \mathrm{~A}$
c. $7.83 \mathrm{~A}$
d. $1000 \mathrm{~W}$.

Mahipal Kumawat

Numerade Educator

Problem 43

Calculate the assumed current demand of a circuit comprising three shaver units, 1 bell chime transformer, and five $2 \mathrm{amp}$ socket outlets to provide power for table lamps in the sitting area of the property. The final circuit is connected to a consumer unit connected to the $230 \mathrm{~V}$ mains supply.
a. $\quad 23 \mathrm{~mA}$
b. $\quad 43 \mathrm{~mA}$
c. $2.5 \mathrm{~A}$
d. 10A.

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01:45

Problem 44

Calculate the assumed current demand of a cooker having four $3 \mathrm{~kW}$ boiling rings and a $2 \mathrm{~kW}$ oven connected to a $230 \mathrm{~V}$ supply.
a. $14 \mathrm{~kW}$
b. $\quad 15.26 \mathrm{~A}$
c. $25.25 \mathrm{~A}$
d. 10A.

Penny Riley

Numerade Educator

Problem 45

The total current demand of a lighting circuit in an individual household is calculated to be 5A. The current demand applying the diversity factor given in Table A2 of the On Site Guide will be:
a. $\quad 3.3 \mathrm{~A}$
b. $3.75 \mathrm{~A}$
c. $4.5 \mathrm{~A}$
d. $5.0 \mathrm{~A}$.

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Problem 46

The total current demand of a lighting circuit in a small shop is calculated to be 5A. The current demand applying the diversity factor given in Table A2 of the On Site Guide will be:
a. $3.3 \mathrm{~A}$
b. $3.75 \mathrm{~A}$
c. $4.5 \mathrm{~A}$
d. $5 \mathrm{~A}$.

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Problem 47

The total current demand of a lighting circuit in a small hotel is calculated to be 5A. The current demand applying the diversity factor given in Table A2 of the On Site Guide will be:
a. $3.3 \mathrm{~A}$
b. 3.75A
c. $4.5 \mathrm{~A}$
d. $5 \mathrm{~A}$.

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Problem 48

The allowance for diversity on a lighting circuit in an individual household given in Table A2 of the On Site Guide is:
a. none
b. $66 \%$
c. $75 \%$
d. $90 \%$.

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Problem 49

The allowance for diversity on a lighting circuit in business premises given in Table A2 of the On Site Guide is:
a. none
b. $66 \%$
c. $75 \%$
d. $90 \%$.

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Problem 50

The allowance for diversity on a thermostatically controlled water heater in a small hotel given in Table A2 of the On Site Guide is:
a. none
b. $66 \%$
c. $75 \%$
d. $90 \%$.

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Problem 51

The allowance for diversity for 13A socket outlets installed according to the standard arrangements of ring and radial circuits given in Table $\mathrm{H} 2.1$ of the On Site Guide when installed in individual households is:
a. $100 \%$ of all circuits
b. $100 \%$ of the largest circuit $+75 \%$ of every other circuit
c. $100 \%$ of the smallest circuit $+50 \%$ of every other circuit
d. $100 \%$ of the largest circuit $+40 \%$ of every other circuit.

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Problem 52

The allowance for diversity for 13A socket outlets installed according to the standard arrangements of ring and radial circuits given in Table $\mathrm{H} 2.1$ of the On Site Guide when installed in offices and business premises is:
a. $100 \%$ of all circuits
b. $100 \%$ of the largest circuit $+75 \%$ of every other circuit
c. $100 \%$ of the largest circuit $+50 \%$ of every other circuit
d. $100 \%$ of the largest circuit $+40 \%$ of every other circuit.

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Problem 53

The current carrying-capacity of a two-core single-phase $2.5 \mathrm{~mm}$ nonarmoured PVC cable enclosed in trunking as given in Table F5 (i) of the On Site Guide or Table 6.6 of this book is:
a. $\quad 18 \mathrm{~A}$
b. $23 \mathrm{~A}$
c. $27 \mathrm{~A}$
d. $30 \mathrm{~A}$.

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Problem 54

The current-carrying capacity of a two-core single-phase $2.5 \mathrm{~mm}$ nonarmoured PVC cable clipped direct to a wall as given in Table F5 (i) of the On Site Guide or Table 6.6 of this book is:
a. $18 \mathrm{~A}$
b. $23 \mathrm{~A}$
c. $27 \mathrm{~A}$
d. $30 \mathrm{~A}$.

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Problem 55

The current-carrying capacity of a two-core single-phase $2.5 \mathrm{~mm}$ nonarmoured PVC cable laid on a perforated cable tray or cable basket as given in Table F5 (i) of the On Site Guide or Table 6.6 of this book is:
a. $18 \mathrm{~A}$
b. $23 \mathrm{~A}$
c. $27 \mathrm{~A}$
d. $30 \mathrm{~A}$.

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Problem 56

The volt drop in $\mathrm{mV}$ per ampere per metre of a two-core single-phase $2.5 \mathrm{~mm}$ cable as given in Table F5 ( ii ) of the On Site Guide or Table 6.7 of this book is:
a. 18
b. 11
c. 7.3
d. 4.4.

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Problem 57

The volt drop in $\mathrm{mV}$ per ampere per metre of a two-core single-phase 4.0mm cable as given in Table F5 (ii) of the On Site Guide or Table 6.7 of this book is:
a. 18
b. 11
c. 7.3
d. 4.4.

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Problem 58

The volt drop in $\mathrm{mV}$ per ampere per metre of a two-core single-phase $6.0 \mathrm{~mm}$ cable as given in Table F5 ( ii ) of the On Site Guide or Table 6.7 of this book is:
a. 18
b. 11
c. 7.3
d. 4.4.

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Problem 59

The volt drop in $\mathrm{mV}$ per ampere per metre of a two-core single-phase $10.0 \mathrm{~mm}$ cable as given in Table F5 (ii) of the On Site Guide or Table 6.7 of this book is:
a. 18
b. 11
c. 7.3
d. 4.4.

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01:01

Problem 60

Why does the volt drop in the last four questions, 56 to 59 , decrease as the cable size increases? Remember that $V=I \times R$.
a. volt drop is proportional to resistance
b. volt drop is proportional to temperature
c. as the cable size increases, the resistance of the conductors increases
d. as the cable size increases, the resistance of the conductors decreases.

Khoobchandra Agrawal

Numerade Educator

Problem 61

Ten $1.0 \mathrm{~mm}$ single conductors are to be drawn into a conduit. Use Table E3 of the On Site Guide or Table 6.10 of this book to find the sum of the cable factors for these cables.
a. 16
b. 30
c. 160
d. 300 .

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Problem 62

A 3-metre length of conduit with two bends is to contain the ten $1.0 \mathrm{~mm}$ cables. Determine the size of conduit required using Table E4 of the On Site Guide or Table 6.11 of this book.
a. $16 \mathrm{~mm}$
b. $20 \mathrm{~mm}$
c. $25 \mathrm{~mm}$
d. $32 \mathrm{~mm}$.

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Problem 63

Ten $2.5 \mathrm{~mm}$ single conductors are to be drawn into a conduit. Use Table E3 of the On Site Guide or Table 6.10 of this book to find the sum of the cable factors for these cables.
a. 16
b. 30
c. 160
d. 300 .

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Problem 64

A 3-metre length of conduit with two bends is to contain the ten $2.5 \mathrm{~mm}$ cables. Determine the size of conduit required using Table E4 of the On Site Guide or Table 6.11 of this book.
a. $16 \mathrm{~mm}$
b. $20 \mathrm{~mm}$
c. $25 \mathrm{~mm}$
d. $32 \mathrm{~mm}$.

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Problem 65

Ten $4.0 \mathrm{~mm}$ single conductors are to be drawn into a conduit. Use Table E3 of the On Site Guide or Table 6.10 of this book to find the sum of the cable factors for these cables.
a. 43
b. 160
c. 300
d. 430 .

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Problem 66

A 3-metre length of conduit with two bends is to contain the ten $4.0 \mathrm{~mm}$ cables. Determine the size of conduit required using Table E4 of the On Site Guide or Table 6.11 of this book.
a. $16 \mathrm{~mm}$
b. $20 \mathrm{~mm}$
c. $25 \mathrm{~mm}$
d. $32 \mathrm{~mm}$.

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Problem 67

Ten $1.5 \mathrm{~mm}$ solid PVC cables are to be drawn into trunking. Use Table E5 of the On Site Guide or Table 6.12 of this book to find the sum of the cable factors for these cables.
a. 80
b. 60
c. 40
d. 20 .

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Problem 68

Ten $2.5 \mathrm{~mm}$ solid PVC cables are to be drawn into trunking. Use Table E5 of the On Site Guide or Table 6.12 of this book to find the sum of the cable factors for these cables.
a. 116
b. 117
c. 118
d. 119 .

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Problem 69

Ten $4.0 \mathrm{~mm}$ stranded PVC cables are to be drawn into trunking. Use Table E5 of the On Site Guide or Table 6.12 of this book to find the sum of the cable factors for these cables.
a. 80
b. 119
c. 166
d. 180 .

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Problem 70

Determine the total trunking factor for all 30 cables described in questions 67 to 69 above.
a. 85
b. 155
c. 265
d. 365 .

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Problem 71

Determine the factor for a $75 \mathrm{~mm} \times 75 \mathrm{~mm}$ trunking.
a. 738
b. 1146
c. 1555
d. 2371 .

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Problem 72

What is the maximum number of $4.0 \mathrm{~mm}$ PVC conductors which may be drawn into a $75 \mathrm{~mm} \times 50 \mathrm{~mm}$ trunking?
a. 52
b. 93
c. 110
d. 120 .

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Problem 73

Cutting off the electrical supply to a piece of equipment in order to ensure the safety of those working on it is one definition of:
a. emergency switching
b. functional switching
c. switching for isolation
d. switching for mechanical maintenance.

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Problem 74

Cutting off the full load electrical supply to a piece of equipment in order to ensure the safety of those working on it is one definition of:
a. emergency switching
b. functional switching
c. switching for isolation
d. switching for mechanical maintenance.

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Problem 75

The rapid disconnection of the electrical supply to remove or prevent danger is one definition of:
a. emergency switching
b. functional switching
c. switching for isolation
d. switching for mechanical maintenance.

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Problem 76

Switching electrical equipment in normal service is:
a. emergency switching
b. functional switching
c. switching for isolation
d. switching for mechanical maintenance.

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01:50

Problem 77

Briefly explain why an electrical installation needs protective devices.

Mrinal Rana

Numerade Educator

Problem 78

List the four factors on which the selection of a protective device depends.

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Problem 79

List the five essential requirements for a device designed to protect against overcurrent.

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01:36

Problem 80

Briefly describe the action of a fuse under fault conditions.

Luis Rios

Numerade Educator

Problem 81

State the meaning of 'discrimination' or 'coordination' as applied to circuit protective devices.

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Problem 82

Use a sketch to show how 'discrimination' or 'coordination' can be applied to a piece of equipment connected to a final circuit.

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Problem 83

List typical 'exposed parts' of an installation.

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Problem 84

List typical 'extraneous parts' of a building.

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00:30

Problem 85

Use a sketch to show the path taken by an earth fault current.

Luis Rios

Numerade Educator

Problem 86

Use bullet points and a simple sketch to briefly describe the operation of an RCD.

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Problem 87

State the need for RCDs in an electrical installation:
a. supplying socket outlets with a rated current not exceeding 20A and
b. for use by mobile equipment out of doors as required by IET Regulation 411.3.3.

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Problem 88

Briefly describe an application for RCBOs.

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01:55

Problem 89

In your own words, state the meaning of circuit overload and short-circuit protection. What will provide this type of protection?

Pankaj Jain

Numerade Educator

Problem 90

State the purpose of earthing and earth protection. What do we do to achieve it and why do we do it?

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Problem 91

In your own words, state the meaning of earthing and bonding. What types of cables and equipment would an electrician use to achieve earthing and bonding on an electrical installation?

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Problem 92

In your own words, state what we mean by 'basic protection' and how it is achieved.

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Problem 93

In your own words, state what we mean by 'fault protection' and how it is achieved.

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Problem 94

How does a bar chart help with the organization of a work programme?

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Problem 95

State five methods of making your work area safe on a construction site.

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Problem 96

Why are good relationships important between yourself and the customer and other trades on-site when carrying out work activities?

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Problem 97

Briefly state why time sheets, fully and accurately completed, are important to:
a. an employer
b. an employee.

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Problem 98

State the reasons why you should always present the right image to a client, customer or his representative.

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Problem 99

Briefly describe what we mean by a schedule of work. Who would use a bar chart or schedule of work in your company and why?

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02:14

Problem 100

Changes to the Building Regulations now require an electrician to make 'reasonable provision' for energy-efficient lamps and controls. Use five bullet points to describe what we must now do.

Jennifer Stoner

Numerade Educator

06:27

Problem 101

Briefly describe what the 'code for sustainable homes' aims to do between now and 2016.

Khalida Dawar

Numerade Educator

Problem 102

Briefly describe the importance of 'sustainable design' for buildings and the services within buildings.

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06:27

Problem 103

Use four bullet points to state how the government will achieve level 6 of the code for sustainable homes by 2016 .

Khalida Dawar

Numerade Educator

Problem 104

Describe the procedure for making safe terminations and connections in your electrical work.

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Problem 105

Describe what we mean by a 'maintenance-free' junction box.

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Problem 106

Describe a resin compound joint and give a typical application for such a joint.

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Problem 107

Draw a quick sketch to show the complete earth fault loop path $\mathrm{Z}_{\mathrm{s}}$. Fig 6.11 may give guidance.

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Problem 108

State the meaning of 'diversity' when applied to current demand.

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View

Problem 109

When signing a contract to carry out work described in the contract, what is the electrical contractor actually agreeing to do?

Rashmi Sinha

Numerade Educator

Problem 110

How would you secure each of the following pieces of equipment on-site to prevent theft? Electrical power tools in individual boxes, hand tools in a toolbox, a small aluminium tower scaffold, a bundle of conduit, 203 -metre lengths of trunking and 20 cardboard boxes about $500 \mathrm{~mm}$ square by $50 \mathrm{~mm}$ deep containing LED lighting modules, each retailing at about $£ 90$.

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