What are Cables?

Cables are collections of wires, alternatively referred to as a cord, connector, or plug. They are one or more wires covered in a plastic covering that allows for the transmission of power or data between devices. The earliest use of recognizable electrical cable was the early commercialized telegraph lines. These were iron-made and tedious to produce and install cabling.

Structure of cable

It consists of the following parts:


It allows the current flow comprising of a copper wire. Copper is used extensively since after silver, it has exceptional conducting properties with less resistance towards the flow of current and is less costly, unlike silver. Also, high-quality aluminum, if available can be used.


It is a protective covering around cable which gives damage control caused by water, oil, etc. it prevents leakage of current due to bending. The types of material used are Polyvinyl chloride (PVC) and Cross-Linked Polyethene (XLPE).

Lead Sheath

It’s a metallic sheath made up of aluminum or lead usually coated over the insulator. Used to protect the cable from external factors like moisture, gases, etc.


Provided for protection of the metallic sheath from corrosion, rusting, or any mechanical damage during usage and made of fibrous material like hessian or jute.


Consists of two or more layers of galvanized steel wire or steel tape which is applied on bedding. It serves the purpose to protect the cable from mechanical injury and external damage for a long time after cabling.


Fibrous material layer over armoring to protect it from atmospheric damages.

Broad classification and Types of cables

Cables are classified into the following categories:

Power cord cables

Power Cord Cables are the congregation of two or more electric conductors for transmission of power which is generally held together with an overall sheath. They may be installed as permanent wiring inside the buildings or can be embedded underground, connected overhead, and exposed outside.

Power cables are further classified:

Based on voltage

  Type of Power cable on the basis of Voltage  Voltage Transmission Requirement
  Low Tension Cables  Up to 1000 V (1kV)  
  High Tension Cables  11 kV
  Super Tension Cables  22 kV to 33 kV
  Extra High-Tension Cables  33 kV to 66 kV
  Extra super voltage cables  Above 132 kV

Based on the number of cores

  1. Single power cord core cables are made up of a single conductor formed of copper or aluminum or stands of copper wires twisted pairs together into a single wire and covered usually by PVC insulation widely used for domestic purposes.

2. Two power cord core cables comprise live and neutral cores, made of PVC insulation and are used in the connection of small appliances where there’s no need for earthing as they are double insulated.

3. Three power cord core cables contain live, neutral, and an earth core. To carry current to and from the outlet socket, live and neutral core’s function and to provide a path for the current to connect with the ground, non-insulated earth core is used. Each of the cores has twisted pairs of copper wires.

4. Four power cord core cables have three live cores and one neutral. Each of them is insulated with a color-coded PVC insulation cover and then grouped with an inner sheath layer over it. It is then surrounded by a twisted galvanized steel wire layer for armored protection which protects the cable from rust.

Based on armoring

  1. Armored Cables (Steel Wire Armored or SWA cable) are used for the main electric supply and have mechanical protection, they contain one or two layers of galvanized steel wire. Applications also include underground cabling and are available from 2 core SWA cable to 7 core SWA cable.
  2. Unarmored Cable’s construction is the same but without the armor. With no protection against mechanical damage, they are cheap and thus can be installed in a protected location like inside a wall and used in the control system.

Networking cables

They are associated with the transferring of information moving from one network device to another or connecting various computers with common printers, etc.

Networking cables are further classified as:

  • Coaxial cable

The coaxial cable comprises a single copper conductor at its center and a layer of plastic provides insulation between the conductor and the metal shield (braided). Coaxial cables are used to transmit radio frequency signals, carry television signals for video connection (HDMI Cables), connect computers to LAN (Local Area Network) for cable broadband services like Cat6 cables.

  • Optical fiber cables

They contain numerous optical fibrers which are thin strands of pure glass for transmitting information in the form of light and together all are inside a protected insulated jacket. Used in the transmission of abundant amount of data at high-speed in Internet cables (Cat6), etc.

Cut out view of an optical fiber cable
CC BY-SA 2.5 | Image Credits: https://commons.wikimedia.org | Srleffler
  • Ethernet cable

An Ethernet cable is used to connect devices such as PCs, routers, and switches within a local area network. It is larger with eight wires and resembles a traditional phone cable that has four. Connectors of an Ethernet cable are also larger.

Underground cables

They are buried inside the ground and serve as a replacement for overhead cables which make the place look aesthetically pleasing as there are hidden underneath, also fewer chances of any damage caused with no exposure outside. Used in areas where overhead cables are not feasible to install. View all the cables through image sensors.

Other types of cables include USB-A Cables, HDMI Cables, Cat6 Cables, Lightning Cables, USB-C Cables, D-Sub Cables, Cat8 Cables, etc.

Advantages and disadvantages of cables


  • Minimum damage due to severe weather conditions
  • Negligible transmission loss
  • Twisted pairs of copper since ductile and increase strength
  • More secured in case of underground cables
  • Also, underground cables are subject to less danger of theft, illegal connections etc.
  • View all cables through image sensors when underground to review the pattern


  • Laying of cables needs excavation which is a tedious task, especially in congested places
  • Low flexibility in case of armored cables
  • Repairing of overhead cables easier as compared to underground ones
  • Signal leakage, noise issues when not installed properly

Color coding in cables

  • ‘Hot’ is used for wires carrying current from the main panel to the destination. Colors used are black, red, and white wires with black or red tape. Blue and yellow wires are scarcely used.
  • ‘Neutral’ used for white or grey wires
  • ‘Ground’ used for green and bare copper wires.

How to extend the life of a cable

  • Choose an effective approach
  • Prevent damage
  • Make cable reel adjustments
  • Make repairs on time
  • Maintain Records

Cables used in mobile accessories, computers, and other appliances

Lightning cables used in Apple devices have fewer pins compared to other cables. The lightning cable is associated with iOS version appliances and compatible with the same only.  Cat6 Cables are used for networks of computers reaching 1GB or 1000 Mbps DTR. USB-C cables are compatible with Android versions. HDMI cables connect with television to other devices like laptops etc. for display.

Innovations in cables

The introduction of lightning cables is used to charge and sync Apple devices which are capable of transferring data at a faster rate. The lightning cables are now replaced by Thunderbolt cables. USB-C cables are capable of transferring power and data. USB-C cables are mostly used everywhere which provide 2.5 watts of power. USB-A traditionally used cables for the transfer of files from pen drives to the devices. One can view all the cable types by the use of the latest software provisions. With online purchasing, free shipping on bulk deliveries is possible. Also, free shipping of cables when availing a discount for frequent online customers is available. Free shipping is the best way to engage clients with the temptation to buy more cable products.

Context and Applications

This topic finds its existence in the following courses,

  • Bachelors in Technology (Electrical engineering)
  • Bachelors in Technology (Electronics engineering)
  • Masters in Technology (Electrical engineering)
  • Masters in Technology (Electronics engineering)

Practice Problems

Q1) What material is the conductor made of?

  1. silver
  2. copper
  3. both of the above
  4. none of the above

Correct option: c

Explanation: The conductor material is made up of both silver and copper.

Q2) What is the fullform of XLPE?

  1. Cross-Linked Polyethene
  2. Cross-Linked Polyethylene
  3. Cross-Linked Polypropylene
  4. Linked Polyethylene

Correct option: a

Explanation: The full form of XLPE is Cross-Linked Polyethene.

Q3) What is the purpose of bedding?

  1. Protection form mechanical damage
  2. Protection from rust
  3. Protection from corrosion
  4. Both b and c

Correct option: d

Explanation: The purpose of bedding is protection from corrosion and rust.

Q4) What is the voltage transmission requirement of high-tension cables?

  1. 1 kV
  2. 22 kV to 33 kV
  3. 33 kV to 66 kV
  4. 11 kV

Correct option: d

Explanation: The voltage transmission requirement of high-tension cables is 11 kV.

Q5) What does the color code of Green or bare Copper wires mean?

  1. Neutral
  2. Ground
  3. Hot
  4. Live

Correct option: b

Explanation: The color code of green or bare copper wires means it is for ground.

  • Electrical System
  • Transformers
  • Robotics

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