Q.1 What is the primary purpose of the insulation on a copper conductor in a cable?
To increase the conductivity
To protect against mechanical damage
To prevent electrical short circuits
To reduce the cable weight
Explanation - Insulation provides a non‑conductive barrier that stops current from flowing to unintended paths, avoiding short circuits.
Correct answer is: To prevent electrical short circuits
Q.2 Which material is most commonly used for the outer sheath of underground power cables?
PVC (Polyvinyl Chloride)
Rubber
Polyethylene (PE)
Polypropylene (PP)
Explanation - PE offers excellent water resistance, low moisture absorption, and good mechanical strength, making it ideal for underground use.
Correct answer is: Polyethylene (PE)
Q.3 What does the term 'ampacity' of a cable refer to?
The maximum voltage the cable can handle
The resistance per kilometre of the cable
The current carrying capacity of the cable
The flexibility of the cable
Explanation - Ampacity is the maximum continuous current a cable can carry without exceeding its temperature rating.
Correct answer is: The current carrying capacity of the cable
Q.4 Which of the following cable types is best suited for high‑frequency signal transmission?
Coaxial cable
Twin‑and‑earth cable
Armoured cable
PVC‑sheathed cable
Explanation - Coaxial cables have a central conductor surrounded by a shield and dielectric, providing low loss and shielding for high‑frequency signals.
Correct answer is: Coaxial cable
Q.5 In a three‑core cable, how many insulated conductors are present?
One
Two
Three
Four
Explanation - A three‑core cable contains three separate insulated conductors, each capable of carrying a separate phase or circuit.
Correct answer is: Three
Q.6 What is the main advantage of using aluminium conductors instead of copper in overhead power lines?
Higher conductivity
Lower cost and lighter weight
Better corrosion resistance
Higher tensile strength
Explanation - Aluminium is cheaper and about one‑third the weight of copper, allowing longer spans with less mechanical support.
Correct answer is: Lower cost and lighter weight
Q.7 Which standard defines the classification of fire‑resistant cables in the UK?
IEC 60332
BS 7671
BS 8510
IEC 60884
Explanation - IEC 60332 specifies tests for the fire behaviour of electric cables, including fire‑resistance classifications.
Correct answer is: IEC 60332
Q.8 What does the term 'SKIN EFFECT' describe in AC conductors?
Increase in resistance with temperature
Current concentrating near the surface of the conductor
Reduction of inductance at high frequencies
Loss of insulation strength over time
Explanation - At higher frequencies, alternating current tends to flow near the outer surface of a conductor, effectively reducing the cross‑sectional area used.
Correct answer is: Current concentrating near the surface of the conductor
Q.9 Which cable is specifically designed to be buried directly in the ground without additional protection?
SWA (Steel Wire Armoured) cable
DLO (Direct Lay Overhead) cable
XLPE‑sheathed underground cable
Twin‑and‑earth cable
Explanation - XLPE (cross‑linked polyethylene) insulated cables are rated for direct burial due to their moisture resistance and mechanical toughness.
Correct answer is: XLPE‑sheathed underground cable
Q.10 What is the typical colour coding for a neutral conductor in IEC‑standard wiring?
Red
Blue
Black
Green
Explanation - IEC standards assign blue to the neutral conductor, while brown is used for live and green‑yellow for protective earth.
Correct answer is: Blue
Q.11 Which of the following cable constructions provides the highest protection against mechanical damage?
PVC‑sheathed cable
Armoured cable
Twin‑and‑earth cable
Coaxial cable
Explanation - Armoured cables have steel or aluminium wire armour that protects against impacts, rodents, and crushing forces.
Correct answer is: Armoured cable
Q.12 For a 10 mm² copper conductor, what is the approximate resistance per kilometre at 20 °C?
1.8 Ω/km
0.18 Ω/km
0.018 Ω/km
0.0018 Ω/km
Explanation - The resistivity of copper is about 0.0178 Ω·mm²/m, so 0.0178 Ω·mm²/m ÷ 10 mm² = 0.00178 Ω/m → 1.78 Ω/km ≈ 0.018 Ω/km.
Correct answer is: 0.018 Ω/km
Q.13 Which cable type is most commonly used for low‑voltage domestic lighting circuits in the UK?
SWA cable
Twin‑and‑earth (T&E) cable
Armoured cable
Coaxial cable
Explanation - T&E cable contains a live, neutral, and earth conductor and is the standard for fixed wiring in domestic premises.
Correct answer is: Twin‑and‑earth (T&E) cable
Q.14 What does the abbreviation 'XLPE' stand for in cable terminology?
Extra Light Polyethylene
Cross‑Linked Polyethylene
Extended Life Polyethylene
X‑Laminated Polyethylene
Explanation - XLPE is a form of polyethylene that has been cross‑linked to improve thermal and mechanical properties.
Correct answer is: Cross‑Linked Polyethylene
Q.15 Which property of a cable is most directly affected by the dielectric constant of its insulation material?
Current carrying capacity
Capacitance per unit length
Tensile strength
Thermal resistance
Explanation - The dielectric constant determines how much electric field is stored between conductors, directly influencing capacitance.
Correct answer is: Capacitance per unit length
Q.16 In fire‑rated cables, what does the rating 'Fca' indicate?
Flame spread rating
Fire resistance under load
Flexibility under high temperature
Frequency compensation ability
Explanation - Fca rating means the cable can sustain fire for a specified time while carrying current (load) without failure.
Correct answer is: Fire resistance under load
Q.17 Which of the following is NOT a typical use of coaxial cable?
Television signal distribution
High‑speed data networking
Power distribution for machinery
Radio frequency (RF) transmission
Explanation - Coaxial cables are designed for high‑frequency signal transmission, not for carrying large power currents.
Correct answer is: Power distribution for machinery
Q.18 What is the purpose of the metallic shield in a shielded twisted‑pair (STP) cable?
To increase the cable's tensile strength
To prevent moisture ingress
To reduce electromagnetic interference (EMI)
To provide a ground path for fault currents
Explanation - The shield acts as a Faraday cage, limiting external electromagnetic fields from affecting the signal conductors.
Correct answer is: To reduce electromagnetic interference (EMI)
Q.19 Which conductor material has a higher resistivity: copper or aluminium?
Copper
Aluminium
Both have equal resistivity
It depends on temperature
Explanation - Aluminium's resistivity (~2.82 µΩ·cm) is about 1.6 times that of copper (~1.68 µΩ·cm), making it less conductive per unit cross‑section.
Correct answer is: Aluminium
Q.20 What does the term 'voltage rating' of a cable specify?
Maximum current the cable can carry
Maximum operating temperature
Maximum voltage the insulation can safely withstand
Minimum insulation thickness
Explanation - Voltage rating indicates the highest potential difference the cable's insulation can tolerate without breakdown.
Correct answer is: Maximum voltage the insulation can safely withstand
Q.21 Which cable type is commonly used for data transmission in Ethernet networks?
Unshielded Twisted Pair (UTP) cable
Coaxial cable
Armoured cable
Fiber optic cable
Explanation - UTP cables such as Cat5e, Cat6, and Cat6a are standard for Ethernet due to cost effectiveness and performance.
Correct answer is: Unshielded Twisted Pair (UTP) cable
Q.22 What is the typical colour for a protective earth (PE) conductor in IEC wiring?
Red
Blue
Green‑Yellow
Brown
Explanation - The IEC colour code assigns a green‑yellow striped colour to protective earth conductors.
Correct answer is: Green‑Yellow
Q.23 A cable with a 'single core' construction means:
It has one insulated conductor only
It contains one pair of conductors
It has a single metallic shield
It is meant for single‑phase applications only
Explanation - Single‑core cables consist of a single insulated conductor, often used where a single line is required.
Correct answer is: It has one insulated conductor only
Q.24 Which factor most influences the ampacity of a cable?
Length of the cable
Ambient temperature
Number of conductors
Colour of the insulation
Explanation - Higher surrounding temperatures reduce the cable’s ability to dissipate heat, lowering its permissible current.
Correct answer is: Ambient temperature
Q.25 What does the abbreviation 'PVC' stand for in cable insulation?
Polyvinyl Chloride
Polyvinyl Carbonate
Polyvalent Chloride
Polyvinyl Cobalt
Explanation - PVC is a common thermoplastic material used for insulation due to its good mechanical and fire‑retardant properties.
Correct answer is: Polyvinyl Chloride
Q.26 In a three‑core and earth cable, how many insulated conductors are present?
Two
Three
Four
Five
Explanation - Three insulated cores for phases plus one insulated earth conductor make up a three‑core and earth cable.
Correct answer is: Four
Q.27 Which cable is designed to minimise electromagnetic radiation emissions?
Twisted pair cable
Coaxial cable
Unshielded cable
Flat ribbon cable
Explanation - Coaxial cables confine the electromagnetic field within the dielectric, reducing radiation.
Correct answer is: Coaxial cable
Q.28 What is the typical voltage rating for a standard low‑voltage (LV) power cable used in residential wiring?
50 V
240 V
600 V
1000 V
Explanation - In many regions, LV residential circuits are rated for up to 240 V AC (or 120 V in some countries).
Correct answer is: 240 V
Q.29 Which of the following cable types is most suitable for use in a marine environment?
PVC‑sheathed cable
Rubber‑insulated cable
Marine‑grade tinned copper cable
Standard twin‑and‑earth cable
Explanation - Tinned copper resists corrosion from saltwater, making it ideal for marine applications.
Correct answer is: Marine‑grade tinned copper cable
Q.30 The term 'thermal rating' of a cable refers to:
Maximum temperature the insulation can withstand
Maximum current without exceeding a specified conductor temperature
Maximum ambient temperature for installation
Heat resistance of the outer sheath
Explanation - Thermal rating defines the current limit that keeps the conductor temperature within safe limits.
Correct answer is: Maximum current without exceeding a specified conductor temperature
Q.31 Which type of cable is most commonly used for connecting a computer to a monitor?
Coaxial cable
HDMI cable
Twin‑and‑earth cable
Fiber optic cable
Explanation - HDMI transmits digital video and audio signals between devices such as computers and monitors.
Correct answer is: HDMI cable
Q.32 What does the abbreviation 'SWA' stand for in cable construction?
Steel Wire Armoured
Standard Wire Aluminium
Solid Wire Assembly
Super Wide Area
Explanation - SWA cables have a steel wire armour for mechanical protection, commonly used in industrial installations.
Correct answer is: Steel Wire Armoured
Q.33 For a cable installed in a conduit, which factor can increase its ampacity compared to free‑air installation?
Reduced ambient temperature
Higher conduit temperature rating
Improved heat dissipation due to enclosed space
Increased number of conductors
Explanation - If the conduit is in a cooler environment, the cable can dissipate heat more effectively, allowing higher current.
Correct answer is: Reduced ambient temperature
Q.34 Which of the following is a characteristic of a fire‑retardant (FR) cable?
It self‑extinguishes when exposed to flame
It conducts electricity without resistance
It can carry double the normal current
It has a metallic outer sheath
Explanation - FR cables are designed to stop burning and limit flame spread, often self‑extinguishing after flame removal.
Correct answer is: It self‑extinguishes when exposed to flame
Q.35 Which material is most often used for the core of a high‑voltage underground cable?
Aluminium
Copper
Silver
Gold
Explanation - Aluminium offers a good balance of conductivity, weight, and cost for high‑voltage applications.
Correct answer is: Aluminium
Q.36 What is the main advantage of using a multi‑core cable versus separate single‑core cables?
Reduced overall resistance
Simplified installation and space saving
Higher current rating per core
Improved thermal performance
Explanation - Multi‑core cables bundle several conductors together, reducing the number of individual cables to handle.
Correct answer is: Simplified installation and space saving
Q.37 In IEC colour coding, which colour is used for a protective earth (PE) conductor in a two‑core cable?
Blue
Brown
Green‑Yellow
Red
Explanation - The green‑yellow striped colour is reserved for protective earth regardless of cable core count.
Correct answer is: Green‑Yellow
Q.38 Which of the following cable types is designed to operate in temperatures up to 200 °C?
PVC‑sheathed cable
Silicone‑rubber insulated cable
XLPE‑sheathed cable
Standard rubber cable
Explanation - Silicone rubber can withstand very high temperatures, making it suitable for high‑temperature environments.
Correct answer is: Silicone‑rubber insulated cable
Q.39 What does the term 'shield' refer to in a shielded cable?
A layer of extra insulation
A conductive layer that encloses the conductors
A protective outer jacket
A reinforcement of steel wires
Explanation - The shield is a metallic (foil or braid) layer that surrounds the signal conductors to block interference.
Correct answer is: A conductive layer that encloses the conductors
Q.40 Which cable type is typically used for connecting a TV antenna to a television set?
Coaxial cable
Twin‑and‑earth cable
Armoured cable
Fiber optic cable
Explanation - Coaxial cables have the low loss and shielding needed for RF signals from an antenna.
Correct answer is: Coaxial cable
Q.41 What is the main effect of increasing the number of strands in a flexible conductor?
Increases resistance
Improves flexibility
Reduces ampacity
Decreases skin effect
Explanation - More, smaller strands allow the conductor to bend more easily while maintaining overall cross‑section.
Correct answer is: Improves flexibility
Q.42 Which standard specifies the requirements for PVC‑insulated cables for household wiring in the UK?
BS 7671
BS 8544
BS 6397
BS 6004
Explanation - BS 6397 covers the specifications for PVC‑insulated, non‑armoured cables used in domestic wiring.
Correct answer is: BS 6397
Q.43 What is the typical cross‑sectional area of a 1 mm² copper conductor?
1 mm²
0.5 mm²
2 mm²
0.75 mm²
Explanation - By definition, a 1 mm² conductor has a cross‑sectional area of 1 mm².
Correct answer is: 1 mm²
Q.44 Which cable construction is most suitable for high‑speed data transmission over long distances?
Copper twisted pair
Coaxial cable
Fiber optic cable
Armoured steel cable
Explanation - Fiber optics transmit light signals, providing very high bandwidth with low attenuation over long distances.
Correct answer is: Fiber optic cable
Q.45 When two conductors are twisted together, what primary benefit does this provide?
Increased current capacity
Reduced electromagnetic interference
Improved mechanical strength
Lower resistance
Explanation - Twisting causes the magnetic fields generated by each conductor to cancel out, reducing EMI.
Correct answer is: Reduced electromagnetic interference
Q.46 What does the abbreviation 'MOP' stand for in cable terminology?
Maximum Operating Pressure
Minimum Operating Power
Maximum Operating Temperature
Medium‑Opacity Polymer
Explanation - MOP indicates the highest temperature at which a cable can safely operate.
Correct answer is: Maximum Operating Temperature
Q.47 Which cable type is specifically designed for use in fire‑safety lighting circuits?
Fire‑resistant (FR) cable
Armoured cable
Twin‑and‑earth cable
Coaxial cable
Explanation - FR cables maintain circuit integrity during a fire, ensuring emergency lighting continues to function.
Correct answer is: Fire‑resistant (FR) cable
Q.48 If a cable's insulation is damaged, which of the following hazards is most likely to occur?
Overheating of the conductor
Reduction of voltage rating
Increase in tensile strength
Decrease in ampacity
Explanation - Exposed conductors can cause arcing or short circuits, leading to overheating and fire risk.
Correct answer is: Overheating of the conductor
Q.49 Which of the following is a benefit of using a multi‑core cable with individual colour‑coded insulation for each core?
Higher voltage rating
Easier identification during installation
Reduced cost
Increased flexibility
Explanation - Colour coding each core allows installers to quickly recognize phase, neutral, and earth conductors.
Correct answer is: Easier identification during installation
Q.50 What does the term 'dielectric strength' of a cable's insulation refer to?
Maximum mechanical stress the insulation can endure
Maximum voltage the insulation can withstand before breakdown
Thermal conductivity of the insulation
Resistance to chemical corrosion
Explanation - Dielectric strength measures the voltage at which the insulating material fails electrically.
Correct answer is: Maximum voltage the insulation can withstand before breakdown
Q.51 In a cable schedule, the designation '3×2.5 mm²' indicates:
Three conductors each of 2.5 mm² cross‑section
Two conductors each of 3 mm² cross‑section
Three cores, each with 2.5 mm² area, plus an earth
A single conductor with 7.5 mm² area
Explanation - The format 'n×A' specifies the number of cores (n) and the cross‑sectional area (A) of each core.
Correct answer is: Three conductors each of 2.5 mm² cross‑section
Q.52 Which cable is most appropriate for a portable appliance that requires high flexibility?
SWA cable
Flexible rubber‑insulated cable
Armoured steel cable
PVC‑sheathed fixed cable
Explanation - Rubber insulation provides high flexibility and durability for portable equipment.
Correct answer is: Flexible rubber‑insulated cable
Q.53 What is the primary reason for using a larger cross‑sectional area for a cable carrying higher current?
To reduce the weight of the cable
To lower the resistance and heat generated
To increase the voltage rating
To improve flexibility
Explanation - Larger cross‑section reduces resistive losses, allowing more current without overheating.
Correct answer is: To lower the resistance and heat generated
Q.54 Which type of cable is typically used for connecting a computer to a router for Ethernet networking?
Cat5e/Cat6 UTP cable
Coaxial cable
Twin‑and‑earth cable
Fiber optic cable
Explanation - Unshielded twisted pair (UTP) categories 5e or 6 support Gigabit Ethernet connections.
Correct answer is: Cat5e/Cat6 UTP cable
Q.55 What does the term 'buried depth' refer to in cable installation standards?
The distance between the cable and the nearest wall
The depth of the trench in which the cable is laid
The thickness of the cable's outer sheath
The length of the cable run
Explanation - Buried depth ensures adequate protection from mechanical damage and temperature effects.
Correct answer is: The depth of the trench in which the cable is laid
Q.56 Which of the following is a typical characteristic of a low‑smoke zero halogen (LSZH) cable?
It emits no smoke when burnt
It conducts electricity without resistance
It is fire‑proof and cannot burn
It has a metallic outer jacket
Explanation - LSZH cables produce minimal smoke and no halogen gases when exposed to fire, improving safety in confined spaces.
Correct answer is: It emits no smoke when burnt
Q.57 In a 4‑core cable used for three‑phase power, what is the purpose of the fourth core?
It carries a spare phase
It serves as the protective earth
It doubles the current capacity
It is for neutral
Explanation - In three‑phase systems, a fourth core is commonly used as an earth conductor for safety.
Correct answer is: It serves as the protective earth
Q.58 Which of the following statements about the skin effect is true?
It decreases with increasing frequency
It causes current to flow mainly at the centre of the conductor
It increases the effective resistance at high frequencies
It only occurs in non‑metallic conductors
Explanation - Skin effect forces AC to flow near the surface, reducing effective cross‑section and raising resistance at high frequencies.
Correct answer is: It increases the effective resistance at high frequencies
Q.59 What is the typical colour for a live (phase) conductor in a single‑phase IEC system?
Blue
Brown
Green‑Yellow
Black
Explanation - IEC colour code uses brown for the active/live conductor; blue is neutral.
Correct answer is: Brown
Q.60 Which of the following factors does NOT directly affect the voltage drop in a cable run?
Cable length
Conductor resistance
Ambient temperature
Cable colour
Explanation - Voltage drop depends on resistance, length, current, and temperature, not the colour of the insulation.
Correct answer is: Cable colour
Q.61 When a cable is rated for 600 V, what does this imply?
It can safely operate at any voltage up to 600 V
It will always carry 600 V regardless of load
It is designed for DC use only
It cannot be used for AC applications
Explanation - The voltage rating is the maximum permissible operating voltage for the insulation.
Correct answer is: It can safely operate at any voltage up to 600 V
Q.62 Which cable type is most suitable for a high‑temperature industrial motor that operates at 150 °C?
PVC‑sheathed cable
Silicone rubber‑insulated cable
XLPE‑sheathed cable
Rubber‑insulated cable
Explanation - Silicone rubber retains flexibility and electrical properties up to about 200 °C, making it fit for high‑temperature motors.
Correct answer is: Silicone rubber‑insulated cable
Q.63 What is the purpose of a fire‑stop cable in a building fire alarm system?
To prevent fire spread through cable routes
To increase the cable's ampacity
To improve signal quality
To reduce cable weight
Explanation - Fire‑stop cables are designed to maintain circuit continuity while limiting fire propagation through penetrations.
Correct answer is: To prevent fire spread through cable routes
Q.64 In a cable with a steel wire armour (SWA), what additional protection does the armour provide besides mechanical strength?
Electrical insulation
Electromagnetic shielding
Thermal resistance
Chemical resistance
Explanation - The steel armour can act as a shield against external electromagnetic fields.
Correct answer is: Electromagnetic shielding
Q.65 What is the main disadvantage of using copper conductors compared to aluminium for long distance transmission?
Higher resistivity
Heavier weight
Lower tensile strength
Higher cost
Explanation - Copper is more expensive than aluminium, making cost the primary drawback for long‑distance lines.
Correct answer is: Higher cost
Q.66 Which of the following is true about a 'sheathed' cable?
It has a metallic armour for protection
It contains a protective outer layer that encases the conductors
It is always fire‑resistant
It can only be used underground
Explanation - Sheathing provides environmental protection, mechanical protection, and sometimes fire resistance.
Correct answer is: It contains a protective outer layer that encases the conductors
Q.67 What does the term 'twist pitch' refer to in twisted‑pair cables?
The number of twists per metre
The angle of each twist
The diameter of the cable
The thickness of the insulation
Explanation - Twist pitch is the number of twists per unit length, influencing EMI reduction and impedance.
Correct answer is: The number of twists per metre
Q.68 Which of the following is NOT a typical cause of cable degradation over time?
UV exposure
Mechanical abrasion
Repeated bending
Colour fading
Explanation - Colour fading is cosmetic; UV, abrasion, and bending can physically damage insulation and conductors.
Correct answer is: Colour fading
Q.69 What is the typical voltage class for a low‑voltage cable used in residential lighting?
≤ 50 V
≤ 1000 V
≤ 10 kV
≤ 35 kV
Explanation - Low‑voltage cables are usually rated up to 1000 V for domestic and commercial installations.
Correct answer is: ≤ 1000 V
Q.70 Which cable type would you select for a fire‑safety system that must continue operating for at least 30 minutes during a fire?
Fire‑resistant (FR) cable
Armoured cable
PVC‑sheathed cable
Twin‑and‑earth cable
Explanation - FR cables are specifically tested to maintain functionality for a set fire duration.
Correct answer is: Fire‑resistant (FR) cable
Q.71 What does the abbreviation 'EPR' stand for in cable insulation materials?
Ethylene Propylene Rubber
Electrical Power Resistance
Expanded Plastic Resin
Energized Polymer Rubber
Explanation - EPR is a synthetic rubber offering good heat and weather resistance for cable insulation.
Correct answer is: Ethylene Propylene Rubber
Q.72 When a cable is described as 'flexible', which design feature is most responsible for this property?
Use of stranded conductors
Thicker outer sheath
Higher voltage rating
Larger cross‑sectional area
Explanation - Stranded conductors consist of many small wires, allowing the cable to bend without breaking.
Correct answer is: Use of stranded conductors
Q.73 Which of the following cable types is most suitable for aerial (overhead) installations?
SWA cable
Underground XLPE cable
Twin‑and‑earth cable
Fiber optic cable
Explanation - SWA cables are robust, have mechanical protection, and are commonly used for overhead lines.
Correct answer is: SWA cable
Q.74 What is the main function of a cable's 'grounding conductor'?
To carry the main load current
To provide a return path for fault currents
To increase the cable's voltage rating
To act as a shielding layer
Explanation - The grounding (protective earth) conductor ensures safety by carrying fault currents to earth.
Correct answer is: To provide a return path for fault currents
Q.75 If a cable's outer sheath is made of PVC, which property is generally expected?
High fire‑resistance rating
Excellent resistance to oil and chemicals
Good flexibility at low temperatures
High temperature tolerance above 150 °C
Explanation - PVC remains flexible at lower temperatures but is limited in high‑temperature environments.
Correct answer is: Good flexibility at low temperatures
Q.76 Which cable is most appropriate for connecting a CCTV camera to a recording system over a distance of 200 m?
Coaxial RG‑59 cable
Cat5e/Cat6 UTP cable
Twin‑and‑earth cable
Armoured steel cable
Explanation - Coaxial cable provides low‑loss transmission of video signals over moderate distances.
Correct answer is: Coaxial RG‑59 cable
Q.77 What is the purpose of a 'cable tray' in an installation?
To protect cables from UV radiation
To provide a pathway for cable support and organization
To increase the ampacity of the cables
To act as a fire‑resistant barrier
Explanation - Cable trays hold and organize cables, simplifying installation and maintenance.
Correct answer is: To provide a pathway for cable support and organization
Q.78 In a power cable, the term 'conductor' refers to:
The outer protective jacket
The metal material that carries current
The insulation surrounding the metal
The grounding wire
Explanation - The conductor is the electrical path (usually copper or aluminium) that transports current.
Correct answer is: The metal material that carries current
Q.79 Which of the following cables is typically used for high‑speed data transmission in data centers?
Cat6a UTP cable
Twin‑and‑earth cable
Coaxial cable
Armoured cable
Explanation - Cat6a supports 10 Gbps Ethernet up to 100 m, making it common in data centers.
Correct answer is: Cat6a UTP cable
Q.80 What does the abbreviation 'THHN' indicate in US cable specifications?
Thermoplastic High Heat‑resistant Nylon
Thermoplastic Heat‑and‑Nylon
Thermoplastic High‑Heat Nylon‑coated
Thermo‑Hard Nylon
Explanation - THHN describes a type of insulation that is heat‑resistant and suitable for dry and wet locations.
Correct answer is: Thermoplastic High Heat‑resistant Nylon
Q.81 Which factor is the most critical when selecting a cable for a high‑frequency (RF) application?
Conductor material
Dielectric loss of the insulation
Cable colour
Mechanical strength
Explanation - Low dielectric loss ensures minimal signal attenuation at high frequencies.
Correct answer is: Dielectric loss of the insulation
Q.82 What is the typical purpose of a 'drain wire' in a shielded cable?
To carry the main signal
To provide a path for electrostatic discharge to ground
To increase the cable's tensile strength
To improve heat dissipation
Explanation - The drain wire is bonded to the shield and facilitates grounding of the shield.
Correct answer is: To provide a path for electrostatic discharge to ground
Q.83 When a cable is said to have a 'rated temperature of 90 °C', what does this imply?
The cable cannot be used above 90 °C ambient temperature
The conductor temperature may reach up to 90 °C during operation
The insulation will melt at 90 °C
The cable is fire‑proof up to 90 °C
Explanation - The rating defines the maximum temperature the conductor can safely attain while carrying current.
Correct answer is: The conductor temperature may reach up to 90 °C during operation
Q.84 Which type of cable is most commonly used for connecting a generator to a switchboard in a power plant?
Armoured steel cable
XLPE‑sheathed high‑voltage cable
Twin‑and‑earth cable
Coaxial cable
Explanation - XLPE insulation handles high voltages and temperatures typical of generator connections.
Correct answer is: XLPE‑sheathed high‑voltage cable
Q.85 What is the effect of adding a metallic shield to a cable on its capacitance?
Capacitance decreases
Capacitance remains unchanged
Capacitance increases
Capacitance becomes zero
Explanation - The shield adds a conductive surface close to the conductors, raising the capacitance per unit length.
Correct answer is: Capacitance increases
Q.86 Which of the following is the most suitable cable for a portable audio speaker system that requires flexibility and low weight?
Heavy‑duty armoured cable
Silicone rubber‑insulated flexible cable
PVC‑sheathed twin‑and‑earth cable
Coaxial cable
Explanation - Silicone insulation provides flexibility, low weight, and good electrical performance for audio applications.
Correct answer is: Silicone rubber‑insulated flexible cable
Q.87 What does the term 'continuous rating' of a cable refer to?
The maximum current for short duration overloads
The maximum current the cable can carry indefinitely
The voltage rating for intermittent use
The temperature rating for a single use
Explanation - Continuous rating is the current level a cable can sustain without exceeding its temperature limits over unlimited time.
Correct answer is: The maximum current the cable can carry indefinitely
Q.88 Which of the following cables is typically used for high‑speed digital video transmission in broadcast studios?
HDMI cable
Coaxial RG‑6 cable
Twin‑and‑earth cable
Armoured steel cable
Explanation - HDMI supports high‑definition video and audio signals with digital transmission.
Correct answer is: HDMI cable
Q.89 In cable terminology, what does the abbreviation 'PVC' indicate about the material used?
Polyvinyl Chloride, a thermoplastic insulator
Polyvinyl Carbonate, a conductive polymer
Polyvinyl Ceramic, a high‑temperature material
Polyvinyl Composite, a metal alloy
Explanation - PVC is widely used for its flexibility, durability, and fire‑retardant properties.
Correct answer is: Polyvinyl Chloride, a thermoplastic insulator
Q.90 Which property of a cable is most directly affected by increasing the conductor's temperature?
Electrical resistance
Dielectric strength
Mechanical flexibility
Colour of the insulation
Explanation - Resistance of conductors rises with temperature, leading to higher I²R losses.
Correct answer is: Electrical resistance
Q.91 What does the abbreviation 'SWG' stand for when describing the size of steel wire armour?
Standard Wire Gauge
Steel Wire Grade
Standard Wire Gauge
Super Wire Guard
Explanation - SWG is a British standard for measuring the diameter of wire, used for armour sizing.
Correct answer is: Standard Wire Gauge
Q.92 Which of the following cable types is most commonly used for connecting a solar panel array to an inverter?
PV (Photovoltaic) cable with XLPE insulation
Twin‑and‑earth cable
Coaxial cable
Armoured steel cable
Explanation - PV cables are UV‑resistant, have low resistance, and are rated for higher temperatures typical of solar installations.
Correct answer is: PV (Photovoltaic) cable with XLPE insulation
Q.93 Which of the following is a key benefit of using a twisted‑pair cable in Ethernet networking?
Higher voltage rating
Reduced crosstalk and EMI
Increased mechanical strength
Improved fire resistance
Explanation - Twisting the pairs cancels out electromagnetic interference, improving signal integrity.
Correct answer is: Reduced crosstalk and EMI
Q.94 In a 4‑core cable with a cross‑section of 1.5 mm² per core, what is the total copper area?
3.0 mm²
4.5 mm²
6.0 mm²
1.5 mm²
Explanation - Four cores × 1.5 mm² = 6.0 mm² total copper cross‑section.
Correct answer is: 6.0 mm²
Q.95 Which of the following standards deals with the fire performance of cables used in public buildings in the EU?
EN 50575
IEC 60332
BS 7671
ISO 9001
Explanation - EN 50575 specifies fire performance criteria for cables in public and high‑rise buildings within the EU.
Correct answer is: EN 50575
Q.96 What does the term 'concentric shield' refer to in a coaxial cable?
A shield placed around the outer jacket
A metallic foil placed directly over the dielectric surrounding the inner conductor
A braided shield placed inside the inner conductor
A plastic shield that adds mechanical protection
Explanation - The concentric shield is the metallic layer (often foil) that encircles the dielectric, forming the outer conductor of a coaxial cable.
Correct answer is: A metallic foil placed directly over the dielectric surrounding the inner conductor
Q.97 Which of the following is the most common cause of cable failure in outdoor installations?
UV degradation of the outer sheath
Excessive flexibility
Incorrect colour coding
Over‑twisting of conductors
Explanation - Sunlight can break down polymers, making the outer sheath brittle and prone to cracking.
Correct answer is: UV degradation of the outer sheath
Q.98 When a cable is rated as 'single‑core', which of the following statements is true?
It contains one insulated conductor only.
It has one conductor with multiple insulated cores.
It is always used for three‑phase power.
It must have a steel armour.
Explanation - Single‑core cables have a single insulated conductor, often used for individual connections.
Correct answer is: It contains one insulated conductor only.
Q.99 Which cable type is most suitable for an application where low electromagnetic emissions are critical, such as in a medical imaging room?
Shielded twisted pair (STP) cable
Unshielded twisted pair (UTP) cable
Coaxial cable
Armoured steel cable
Explanation - STP provides a grounded shield that greatly reduces EMI, important in sensitive environments.
Correct answer is: Shielded twisted pair (STP) cable
Q.100 What is the typical nominal voltage rating for a standard three‑core and earth (3 C + E) cable used in UK domestic installations?
230 V
300 V
415 V
600 V
Explanation - 3 C + E cables for domestic wiring are generally rated at 300 V (single‑phase) or 450 V (three‑phase).
Correct answer is: 300 V
Q.101 Which of the following describes the primary function of a 'cable gland'?
To increase the ampacity of a cable
To provide a secure, sealed entry point for a cable through a panel
To change the colour of the cable sheath
To reduce the cable's resistance
Explanation - Cable glands clamp and seal the cable, maintaining environmental protection and strain relief.
Correct answer is: To provide a secure, sealed entry point for a cable through a panel
Q.102 What does the abbreviation 'VDE' refer to in the context of cable standards?
Verband der Elektrotechnik, a German Association for Electrical Engineering
Voltage Direct Energy
Variable Dielectric Elastomer
Vibration Damping Element
Explanation - VDE is a German certification body that sets safety and performance standards for electrical equipment, including cables.
Correct answer is: Verband der Elektrotechnik, a German Association for Electrical Engineering
Q.103 Which of the following cable constructions provides the highest degree of fire resistance?
LSZH (Low Smoke Zero Halogen) cable
Armoured steel cable
Fire‑resistant (FR) cable with mineral insulation
PVC‑sheathed cable
Explanation - Mineral‑filled insulation can sustain fire for longer periods while maintaining circuit integrity.
Correct answer is: Fire‑resistant (FR) cable with mineral insulation
Q.104 If a cable's cross‑section is increased from 2.5 mm² to 4 mm², what is the approximate change in its resistance per kilometre (assuming copper conductors)?
Resistance halves
Resistance reduces by about 37 %
Resistance doubles
Resistance remains unchanged
Explanation - Resistance ∝ 1/area. Ratio = 2.5/4 = 0.625 → 37.5 % reduction.
Correct answer is: Resistance reduces by about 37 %
Q.105 Which cable type would you select for a high‑current, short‑run connection between a motor and its starter?
Twin‑and‑earth (T&E) cable
Armoured steel cable
Heavy‑duty flexible copper cable (e.g., H07RN‑F)
Coaxial cable
Explanation - Heavy‑duty flexible cables can handle high current and frequent movement typical of motor connections.
Correct answer is: Heavy‑duty flexible copper cable (e.g., H07RN‑F)
Q.106 Which of the following is a common test method for checking the continuity of a cable?
Insulation resistance test
Voltage drop test
Continuity (ohmmeter) test
Partial discharge test
Explanation - A simple resistance measurement verifies that the conductor is unbroken.
Correct answer is: Continuity (ohmmeter) test
Q.107 What does the abbreviation 'PVC‑PVC' refer to in cable construction?
PVC conductor with PVC outer sheath
PVC insulation with PVC outer jacket
PVC sheath with PVC armouring
PVC core with PVC shielding
Explanation - PVC‑PVC cables have both the insulation and the outer sheath made of PVC.
Correct answer is: PVC insulation with PVC outer jacket
Q.108 Which cable type is commonly used for connecting a telephone line to a house?
Category 5e cable
Twisted pair telephone cable (e.g., 4‑core 0.8 mm²)
Coaxial RG‑58 cable
Twin‑and‑earth cable
Explanation - Standard telephone lines use twisted‑pair copper cables with small cross‑section conductors.
Correct answer is: Twisted pair telephone cable (e.g., 4‑core 0.8 mm²)
Q.109 Which factor most directly influences the selection of a cable's armour type?
Required voltage rating
Mechanical protection needed
Desired colour of the cable
Cable's fire‑rating
Explanation - Armour is primarily added to guard against physical damage, impact, and rodent attacks.
Correct answer is: Mechanical protection needed
Q.110 What is the purpose of a 'neutral conductor' in an AC power system?
To carry fault currents
To complete the return path for current
To protect against over‑voltage
To increase system capacitance
Explanation - The neutral provides a return path for unbalanced loads, maintaining circuit continuity.
Correct answer is: To complete the return path for current
Q.111 In cable sizing, the term 'derating factor' is used to:
Increase the voltage rating of a cable
Reduce the ampacity due to external conditions
Change the colour of the cable insulation
Calculate the cable's tensile strength
Explanation - Derating accounts for factors such as temperature, bundling, and installation method that lower permissible current.
Correct answer is: Reduce the ampacity due to external conditions
Q.112 Which of the following is a primary reason for using a multi‑core cable instead of separate single‑core cables in a control panel?
Higher current rating
Reduced installation space and easier routing
Higher voltage rating
Improved fire resistance
Explanation - Multi‑core cables consolidate several conductors, simplifying panel layout and reducing clutter.
Correct answer is: Reduced installation space and easier routing
Q.113 Which of the following is NOT an advantage of using XLPE insulation over PVC?
Higher temperature rating
Better resistance to moisture
Lower cost
Lower dielectric loss at high frequencies
Explanation - XLPE is generally more expensive than PVC, despite offering superior thermal and electrical properties.
Correct answer is: Lower cost
Q.114 What is the typical colour coding for a protective earth conductor in a 2‑core cable according to IEC standards?
Blue
Brown
Green‑Yellow
Black
Explanation - Green‑yellow striped insulation is reserved for protective earth conductors.
Correct answer is: Green‑Yellow
Q.115 Which of the following cables is best suited for high‑frequency (GHz) applications such as microwave transmission?
Coaxial cable with low‑loss dielectric
Twin‑and‑earth cable
Armoured steel cable
PVC‑sheathed cable
Explanation - Low‑loss coaxial cables maintain signal integrity at microwave frequencies.
Correct answer is: Coaxial cable with low‑loss dielectric
Q.116 In a cable schedule, the notation '2×1.5 mm² SWA' indicates:
Two steel wire armoured conductors of 1.5 mm² each
Two cores each of 1.5 mm² with steel wire armour
A single 3.0 mm² steel armoured conductor
Two armoured cables each of 1.5 mm² cross‑section
Explanation - The schedule shows the number of cores, their cross‑section, and the presence of SWA.
Correct answer is: Two cores each of 1.5 mm² with steel wire armour
Q.117 Which cable type is typically used for the connection between a TV set and a set‑top box?
HDMI cable
Coaxial RG‑6 cable
Twin‑and‑earth cable
Fiber optic cable
Explanation - HDMI carries both high‑definition video and audio signals between consumer electronics.
Correct answer is: HDMI cable
Q.118 What does the term 'cable impedance' primarily affect in high‑frequency transmission?
Current carrying capacity
Voltage rating
Signal reflection and transmission quality
Mechanical strength
Explanation - Impedance matching prevents reflections and ensures signal integrity in high‑frequency systems.
Correct answer is: Signal reflection and transmission quality
Q.119 Which of the following is a primary cause of increased losses in a cable due to the skin effect?
Higher conductor temperature
Higher frequency of the alternating current
Larger conductor diameter
Thicker insulation
Explanation - Skin effect becomes more pronounced as frequency increases, confining current to a thin layer near the surface.
Correct answer is: Higher frequency of the alternating current
Q.120 Which cable type is most commonly used for connecting a power supply to a computer (the 'mains cord') in Europe?
SWA cable
Twin‑and‑earth (T&E) cable
Coaxial cable
Armoured steel cable
Explanation - T&E cable provides live, neutral, and earth conductors in a flexible sheath for appliance connections.
Correct answer is: Twin‑and‑earth (T&E) cable
Q.121 When a cable is described as 'mineral insulated', what is the main advantage?
Improved flexibility
Higher fire resistance and low smoke emission
Lower cost
Easier installation
Explanation - Mineral‑insulated cables use inorganic materials that resist fire and emit minimal smoke.
Correct answer is: Higher fire resistance and low smoke emission
Q.122 Which of the following statements about 'copper‑clad aluminium' (CCA) conductors is true?
They have the same conductivity as pure copper.
They are cheaper than pure copper and have reduced weight.
They are used only for high‑temperature applications.
They cannot be used for any power transmission.
Explanation - CCA combines a thin copper coating over aluminium, offering lower cost and weight but slightly lower conductivity than pure copper.
Correct answer is: They are cheaper than pure copper and have reduced weight.
Q.123 Which cable construction is typically employed for high‑voltage (HV) transmission lines?
XLPE‑insulated, steel‑wire‑armoured cable
PVC‑sheathed twin‑and‑earth cable
Coaxial cable
Silicone rubber‑insulated flexible cable
Explanation - XLPE provides high dielectric strength, while steel armour adds mechanical protection for HV lines.
Correct answer is: XLPE‑insulated, steel‑wire‑armoured cable
Q.124 In an Ethernet cable, the term 'Category 6A' indicates:
A cable that can support up to 1 Gbps over 100 m
A cable that can support up to 10 Gbps over 100 m
A cable with a steel armour
A cable designed for power transmission only
Explanation - Cat6a is rated for 10 Gbps Ethernet up to 100 m, offering improved shielding and reduced crosstalk.
Correct answer is: A cable that can support up to 10 Gbps over 100 m
Q.125 Which of the following cable types is specifically designed to reduce the risk of fire propagation in aircraft?
Low Smoke Zero Halogen (LSZH) cable
Armoured steel cable
Coaxial cable
Twin‑and‑earth cable
Explanation - LSZH cables emit minimal toxic smoke and halogen gases, meeting stringent aerospace fire safety standards.
Correct answer is: Low Smoke Zero Halogen (LSZH) cable
Q.126 What is the typical cross‑sectional area of a standard domestic lighting circuit conductor in the UK (BS 7671)?
0.5 mm²
1.0 mm²
1.5 mm²
2.5 mm²
Explanation - Lighting circuits are often sized at 1 mm² for short runs, though 1.5 mm² is also common for longer runs.
Correct answer is: 1.0 mm²
Q.127 Which property of a cable determines its ability to resist chemical attack from oils and solvents?
Mechanical strength
Dielectric strength
Chemical resistance of the insulation material
Flexibility
Explanation - The composition of the insulation (e.g., EPDM, EPR) governs resistance to chemicals.
Correct answer is: Chemical resistance of the insulation material
Q.128 In a power distribution system, why is a separate earth conductor required in addition to the neutral?
To carry load current
To provide a low‑impedance path for fault currents to the ground
To increase the system voltage
To reduce the cable's resistance
Explanation - The protective earth ensures safety by safely conducting fault currents away from equipment.
Correct answer is: To provide a low‑impedance path for fault currents to the ground
Q.129 Which cable type is most appropriate for a high‑temperature furnace control circuit?
Silicone rubber‑insulated cable
PVC‑sheathed cable
Twin‑and‑earth cable
Coaxial cable
Explanation - Silicone insulation retains properties at temperatures well above those tolerated by PVC.
Correct answer is: Silicone rubber‑insulated cable
Q.130 What does the abbreviation 'H07RN‑F' signify in a flexible cable rating?
H‑high temperature, 07‑rated voltage, RN‑rubber, F‑flexible
H‑heat resistant, 07‑diameter, RN‑resin, F‑fire resistant
H‑hard, 07‑kilovolt, RN‑neutral, F‑flame retardant
H‑high voltage, 07‑mm², RN‑resistance, F‑flexible
Explanation - H07RN‑F indicates a high‑temperature flexible rubber‑insulated cable with a rated voltage of 450/750 V.
Correct answer is: H‑high temperature, 07‑rated voltage, RN‑rubber, F‑flexible
Q.131 Which of the following is a key advantage of using fibre‑optic cable over copper cable for long‑distance communication?
Higher electrical conductivity
Immunity to electromagnetic interference
Lower installation cost
Greater flexibility
Explanation - Fiber optic cables transmit light, making them unaffected by EMI and suitable for long‑range, high‑bandwidth links.
Correct answer is: Immunity to electromagnetic interference
Q.132 What is the main purpose of a 'cable ladder' in industrial installations?
To provide a grounding path
To support and route multiple cables safely
To increase the ampacity of cables
To act as a fire barrier
Explanation - Cable ladders keep cables organized, allow easy access, and provide support for heavy cable bundles.
Correct answer is: To support and route multiple cables safely
Q.133 Which of the following statements about the 'derating factor' for a cable bundled with other cables is correct?
Derating factor increases the ampacity.
Derating factor is always 1.0 for bundled cables.
Derating factor reduces the permissible current due to reduced heat dissipation.
Derating factor only applies to voltage rating.
Explanation - Bundling limits heat escape, so the cable's ampacity must be reduced using a derating factor.
Correct answer is: Derating factor reduces the permissible current due to reduced heat dissipation.
Q.134 In a cable, the term 'dielectric loss' is most relevant for which type of applications?
High‑current power transmission
High‑frequency signal transmission
Low‑voltage DC circuits
Mechanical support structures
Explanation - Dielectric loss determines how much signal energy is dissipated as heat at high frequencies.
Correct answer is: High‑frequency signal transmission
Q.135 Which cable is most appropriate for connecting a security camera that requires both power and video over a single cable?
Coaxial cable
Power over Ethernet (PoE) Cat6 cable
Twin‑and‑earth cable
Armoured steel cable
Explanation - PoE delivers DC power and Ethernet data over the same twisted‑pair cable, ideal for IP cameras.
Correct answer is: Power over Ethernet (PoE) Cat6 cable
Q.136 What does the term 'cable sheath' refer to?
The inner metallic conductor
The protective outer covering of the cable
The grounding wire within the cable
The twisted pair inside the cable
Explanation - The sheath protects the internal conductors from environmental and mechanical damage.
Correct answer is: The protective outer covering of the cable
Q.137 Which of the following cable types is typically used for a mains power connection in a residential building?
Twin‑and‑earth (T&E) cable
Coaxial cable
Fiber optic cable
Shielded twisted pair (STP) cable
Explanation - T&E provides live, neutral and earth conductors in a flexible sheath, suitable for household wiring.
Correct answer is: Twin‑and‑earth (T&E) cable
Q.138 Which property of a cable is directly affected by the use of a mineral‑filled insulation?
Flexibility
Fire resistance and low smoke emission
Voltage rating
Colour
Explanation - Mineral insulation can withstand higher temperatures and produce minimal smoke when exposed to fire.
Correct answer is: Fire resistance and low smoke emission
Q.139 What is the primary benefit of using a 'braided shield' compared to a 'foil shield' in a cable?
Higher tensile strength
Better protection against low‑frequency EMI
Lower manufacturing cost
Improved fire resistance
Explanation - Braided shields provide a conductive path that is effective against low‑frequency magnetic fields, whereas foil is better for high‑frequency electric fields.
Correct answer is: Better protection against low‑frequency EMI