There at least 12 different power sockets in widespread use around the world! And inevitably, apart from a few cases, like the standardisation of the Type C Europlug in the European Union, you will need a converter when travelling to different countries.Each of the different plugs goes by whatever name their adoptive countries chooses. There are two basic standards for voltage and frequency in the world. One is the North American standard of 110-120 volts at a frequency of 60 Hz, which uses plugs A and B, and the other is the European standard of 220-240 volts at 50 Hz, which uses plugs C through M. The voltage is determined by the corresponding devices used and the country power grids that are being drawn from.Students embarking on City & Guilds NVQ electrical training courses will work with domestic and some industrial plug and socket applications, according to supply voltage and specified usage, to UK British Standards regulations.When electricity was first introduced into households, it was primarily used for lighting. At that time, many electricity companies operated a split-tariff system where the cost of electricity for lighting was lower than that for other purposes. This led to portable appliances (such as vacuum cleaners, electric fans, and hair driers) being connected to the light fitting. However, as electricity became a common method of lighting houses and operating labour-saving appliances, a safe means of connection to the electric system other than using a light socket was needed.The original two pin electrical plug and socket was invented?