Our modern lives revolve around electricity. Nearly every facet of our everyday lives requires electricity. If we look back just 100 years, we had no computers and no internet. When we had a question that needed an answer we were not able to just simply look it up on our favourite search engine like google, rather we would have to go to a library and search mountains of books. Sometimes not even able to find what we were looking for! Just looking at this one example we can see the importance of electricity in our homes. The way we cook, stay warm, and entertain ourselves is slowly, but surely becoming more and more dependent on electricity. So let us explore electricity in the home further.

• Firstly, we are going to explore the definition of electricity in the home.
• After this, we will go deeper into the science by exploring AC and DC currents and cables and which type of electric current we use in our homes.
• Then will explore what the national grid is, how we connect to it, and its significance.
• We will then investigate the uses and applications of electricity in our homes.
• Finally, will discuss the top 5 energy-consuming appliances in the UK.

Electricity in the home definition

Before we discuss and define electricity in the home, it might be helpful to quickly recall exactly what electricity is.

Electricity is transferred into and throughout a home using electrical circuits. The electricity that we use in our homes is generated in power stations, and this energy is then transported around the country by the National Grid. This is also known as mains electricity, which you might have heard abbreviated in real-life conversations as "the mains". Whenever we plug an appliance into a plug socket, whether it be a kettle or an iron, we are connecting to the mains.

Electricity in the home AC or DC

There are two different types of current. Alternating current (AC) and direct current (DC). We will define both of these types of current and then discuss which is primarily used in our homes and why.

Fig. 1 - A diagram showing how DC and AC change their value of current over time.

Alternating current

Alternating currents have two terminals that are the same. The potential difference between the terminals varies as a sine curve. Looking at the diagram below, you can see how the current increases, decreases, reverses direction, and then increases again at regular intervals, rather than staying fixed over time. The magnitude of the current against time resembles a sine wave.

Direct current

Direct currents are very different from alternating currents which periodically change direction. Direct currents are those that you have probably investigated in labs during your science experiments, such as by making and analysing electrical circuits powered by cells or batteries.

AC or DC

The mains electricity is an alternating current, meaning it does not have a positive a negative side to the source. Rather, it has a live wire and a neutral wire which make up each end of a complete electrical circuit. In the UK the electricity supply has a frequency of \(50\,\mathrm{Hz}\), which means the direction of the current changes 50 times per second, back and forth. The mains also supplies a potential difference of \(230\,\mathrm{V}\).

So why do we use alternating current instead of direct current? Well, during the nineteenth-century famous physicist Thomas Edison advocated for dc to be used to power the homes of the world. (Mostly for his own financial benefit.) While Nikola Tesla believed his own alternating current was better suited for this task. This debate between these two titans of physics was known as the War of the Currents.

Unfortunately for Edison, the War of the Currents was ultimately won by Nikola Tesla for the following reasons:

• DC is more expensive to generate than AC.
• DC has much higher energy losses over large distances compared to AC, which is a massive disadvantage when trying to transmit power from power stations over many miles to each individual home.
• The potential difference (voltage) delivered by an alternating current can be increased or decreased as required by a transformer.

Electricity in the home series or parallel

There are two ways to make an electrical circuit with multiple components, series and parallel.

Series circuits

In a series circuit, the current is the same at all different points in the circuit. This means no matter at which point of a circuit you measure the current, it will be the same. Therefore, the exact same amount of current passes through any circuit component at any given point in time. Another feature of any series circuit is that the potential difference from the power source is shared between all the different components.

Fig. 2 - A diagram showing how energy is lost across each component in a DC circuit. The potential difference is shared across each component in a series circuit.

There are some drawbacks to series circuits:

• The different components can’t be switched on and off individually. If we had multiple bulbs in our circuit, we would have to keep them all on.
• When one part breaks down, the whole circuit will stop working. If one bulb breaks in our circuit, nothing else in the circuit will work as the circuit itself will be broken and the current can't flow.

Parallel circuits

A parallel circuit differs fundamentally from a series circuit. The total current supplied by the power source is shared between each circuit component (the amount of current going to each individual component is based on the resistance of the circuit component itself). However, the potential difference across each branch of a parallel circuit is the same.

Series or parallel

So which type of circuit do we use within the home?

If you guessed parallel circuits, you would be right! Imagine if all the light bulbs in your home were connected by one series circuit. If one bulb broke, then you wouldn't be able to light your house until it was replaced. Furthermore, by using circuits in parallel we are able to individually switch on and off each individual bulb using switches conveniently located nearby. I'm sure you can imagine the chaos in your home if you wanted to get an early night's sleep but another family member wanted to stay up late to read if the circuits in your home were connected by series.

Recall that all electrical appliances in the UK are designed to operate at \(230\,\mathrm{V}\). In a parallel circuit, the p.d across each circuit component is the same and can be controlled from the power source. So if \(230\,\mathrm{V}\) is supplied from the mains, then that much voltage will reach each circuit component. If our components were connected in series then each component would not get the voltage required to work properly!

Electricity in the home national grid

The National Grid is a company that distributes electricity throughout the UK. The way it works is that it has a system of cables and transformers. These link various power stations throughout the UK to different points such as homes, factories and buildings.

Cables

A key way in which we connect our appliances to the mains is by using cables. You have likely heard the word cable before and use it fairly often, but it is probably helpful to define the term cable as a scientist would.

Cables are used to connect multiple objects together to facilitate the flow of electrical current between them. The flow of electric charge (electricity) allows us to power our devices from electric generators. Most cables you are familiar with contain multiple, electrically conductive, copper wires that actually transmit the electricity.

Transformers

Contrary to popular belief, in the real world transformers are not giant robots that fight over the fate of the Earth. In the realms of physics and electricity, they have the following definition.

There are two types of transformers that are used for energy to be delivered:

• Step-up transformers increase the voltage and reduce the current through wires, these are typically used at the beginning of the process from the power station.
• Step-down transformers decrease the voltage and increase the current, these are typically used at the end of the process when arriving at their intended destination.

We use transformers to minimise losses in electrical energy when transmitting it over long distances. We need step-up transformers to decrease the current as it travels along cables throughout the country, as a higher current means more energy lost to heat dissipation. However, we need step-down transformers to return the voltage to a safe and desirable level for the appliances in our households.

Uses of electricity in the home

Unless you are a time traveler from the distant past, you already know that there are a variety of ways electricity is used in the home. It is important to remember that not all the appliances in your house run on alternating currents. Some small devices in the home such as your remote controls or torches utilise batteries with a direct current. (These DC devices don't ever connect to the mains, unless for charging, and are a lot cheaper to make a control.)

Some appliances transfer the electrical energy from the mains into kinetic energy to power electric motors. Motors are used in these appliances:

• Washing machines: the motor is used to rotate the drum which washed and/or dried clothes.
• Vacuum cleaners: the motor is used to suction dirt and dust from the floor.
• Fridges/Freezers: the motor is used to compress a type of liquid that can reduce the temperature within the appliance.

Electrical energy is also converted into thermal energy for applications in the home. This is used in appliances such as:

• Kettles: the energy is used to heat water up.
• Radiators: heated water is pumped from a boiler to radiators around the house for warmth.
• Toasters: the heat is used to toast bread.

Top five energy-consuming home appliances

It is important to understand which type of home appliances use the most energy and why. This is important to know, as by being more conscientious with our energy usage we can help protect the environment and save ourselves (or your parents) some money! In order of most to least energy-consuming, these are:

1. Wet appliances: These are the types of appliances that require water such as washing machines and dishwashers. In both of these appliances, water requires energy to be heated up. Then additional energy is needed to pump the hot water as it is needed. To save energy clothes and dishes can be washed at a lower temperature, or in an eco mode.

2. Cold appliances: These appliances include fridges and freezers. They employ motors to compress liquid from a gaseous state into a liquid to help keep a cool temperature inside. These appliances also need to be on 24 hours a day, which requires large amounts of energy. Nevertheless, fridges and freezers typically last for a long time, so if you buy an expensive one that is energy efficient, the high initial investment cost will pay off over time.

3. Consumer technology: This includes laptops, phones and TVs, and more. It is important to remember here that unless you actually turn off these appliances they still use energy in the background. For example, think of your mobile phone. You may have charged it fully the night before, but when you awake the next day, some of the battery has been drained.

4. Lighting: The energy requirements for lighting go up during the cold, winter months when it gets dark much earlier in the day and people go out less. Typically halogen light bulbs were used, but a new alternative is LED lightbulbs which consume much less energy.

5. Cooking appliances: Our final type of appliance is used to cook and heat food. Some examples are microwaves, ovens, and cooking hobs. Generally, microwaves are more efficient compared to ovens, but usually don't offer the best culinary experience. Also, some older cooking appliances still use gas instead of electricity as a source of energy.