 You're on holiday and have been on the beach all day, sharing photos to social media to make your friends jealous. Your phone battery is running low. Then, back in the hotel, disaster strikes. In this video, we're going to look at how different countries have different voltages of electricity and different sockets. When electricity first became available to homes in the 1880s, it was mainly used for lighting. Over the next few decades, other appliances became available and so the plug socket arrangement was needed. At first, plugs were two pins with a live and a neutral pin. To make plugs safer, some countries introduced the third earth pin. This is a safer design that allows electricity to flow to the earth as there is a wire inside the appliance that touches the metal casing of the device. It basically reduces the chances of you having electric shock if something goes wrong. However, not all countries introduced the third earth pin to their plugs. There are now 15 different types of plug sockets all around the world. To learn how a British plug is wired, watch this video. As well as the shapes of plugs and sockets, there are also other key differences between electricity supplies around the world. Different countries use electricity at different voltages. In the American continent, and in Japan, the voltage is 120 volts. Whilst in Europe, the voltage is between 220 and 240 volts. Why isn't there a standard voltage around the world? The answer is down to history. Two men were instrumental in the introduction of electricity. Nikola Tesla in Europe and Thomas Edison in America. Tesla preferred to use electricity at 240 volts, which allowed electricity to travel great distances without a big loss in energy, whilst Edison preferred 110 volts, which was considered safer. Remember, the USA also used the imperial system of measurement, whereas in Europe, the metric system is used. This also influenced the values used. Current systems of electricity use and transport have developed from these two men's original ideas. Luckily, most modern appliances can handle dual voltage. All you need to do is look at the label on the appliance and it will tell you a range of voltages the appliance can work within. For example, this appliance can work at voltages between 100 to 240 volts, so you will need the plug adapter but don't have to worry about the voltage. To learn about the national grid and how electricity is transported, watch this video. It explains the use of transformers that change the voltage of electricity and why they are necessary. So, when you go to a different country, make sure to have the correct adapter for your plugs. Firstly, so they are the right shape, and secondly, so the voltage is compatible.