Cables

When charging your phone has your charging cable suddenly stopped working no matter which way you twist it and how many different sockets you try and plug it into? Well, this typically occurs because of how the different materials that form your charger were put together, not only to charge your phone but also to ensure that no electrical fault will jeopardise your health and safety.

Many aspects of our modern-day lives require electricity, whether this is the phones we use to communicate with or the desktop computers that we use to study. To power our electronics we require cables, sockets and plugs to connect us to the national grid and to do so safely. In this article, we will explore how these electrical components work, their safety features and how they work together.

• Firstly, we will define exactly what a cable is for your foundational knowledge.
• Then we will explore the properties and design of cables that make them work as well as ensure user safety. Short circuits and their relationship to cables will also be discussed.
• Afterwards, we will look at plugs, including what materials they are made from and their features.
• Similarly, we will investigate plug sockets and the different wires contained within.
• Finally, we will briefly discuss how cables connect our electrical devices to the national grid.

Cables and plugs

The insides of our plugs and cables contain a variety of things as seen in the diagram of a UK three-pin plug below.

The casing and grip of the plug are made out of hard plastics which are electrical insulators, their shape is designed in a particular way to ensure that all the wires inside do not touch each other.

Pins

In the UK we have three pins in our plugs that connect to the wires in our cables. The top pin connects to the earth wire, the lower right pin goes to the live wire, and the lower left pin to the neutral wire. These three pins insert easily into any UK plug socket.

All three pins are made out of brass, which is an alloy of copper and zinc. Brass is the perfect material for the pins which are exposed to the surrounding environment by design (so they can be inserted into an external plug socket) as:

• brass is nearly as good of an electrical conductor as copper,
• it does not corrode easily when exposed to air,
• it is a stronger material than pure copper,
• brass is relatively cheap,
• they also have a good visual appeal as brass somewhat resembles gold.

Wires

Let's begin with the Earth wire which connects to the ground in your home. It only carries a current if there is an electrical fault. The Earth wire is made out of copper, so it provides a low-resistant path to the ground. Modern Earth wires in the UK are covered in plastic insulation that is coloured yellow and green. The Earth wire is a great safety feature if a problem occurs. The transmission of electricity will go to the ground instead of anyone touching faulty wiring, preventing an electric shock which can sometimes be fatal.

A neutral wire is covered in blue insulation, this wire is also made out of copper and helps complete our circuit by carrying electricity from our electronics back to the power supply.

Our final wire is the live wire. This is the wire that carries the current used to actually power our electronics. The live wire is cased in brown plastic and carries a voltage of \(230\,\mathrm{V}\).

Fuse

Finally, we have the fuse, which is nestled between the live pin and the live wire. Fuses melt when too much current passes through, this breaks the connection been the live pin and the live wire and causes a short circuit.

Short Circuits

We previously mentioned the role of the fuse, and how it melts and cuts the current. Well, this is where short circuits enter our journey. If a live wire and a neutral wire come into contact with an appliance a very large current will pass both of them, which is called a short circuit. When this takes place, the fuse melts or blows, preventing the flow of current and any accidents.

It is important to remember that we should never touch any exposed wires in a cable regardless of whether an appliance is plugged in. This is because our bodies are not charged and are at \(0\,\mathrm{V}\), if by accident you touch a live wire, a large potential difference will pass through your body, which we feel as an electric shock. This can be very dangerous, sometimes leading to death.

Cables and sockets

Let us define what a socket is.

Sockets are made out of a hard plastic material with three slots for the pins in a UK plug to fit into. They contain wires that connect to cables (usually inside walls). The cables on the other side of a building's plug socket first connect to a fuse box, which then connects to the national grid.

If you have ever observed a plug socket being installed or repaired by an electrician you may have noticed that behind the wall the socket is connected to thick cables. These cables are quite thick as they need to carry a high current from multiple electrical appliances in the same circuit of the building, and being thick increases electrical resistance.