Electrical outlets (also known as outlets, electrical sockets, plugs, and wall plugs) allow electrical equipment to connect to the electrical grid. The electrical grid provides alternating current to the outlet. There are two primary types of outlets: domestic and industrial. While not obvious from looking at them, the two sides of an electrical outlet represent part of a ‘loop of wire’ and plugging an electrical device into that outlet completes that loop, which allows electricity to flow through the device so it can operate. In other words, each side of an electrical outlet acts as a terminal.
Figure 1. Outlet layouts from around the world.
Domestic electrical outlets supply 120 volts in North America and 220-240 volts in Europe, with most nations having outlets supplying voltages similar to one of those two values. Socket size and shape vary greatly from country to country (see figure 1), and for more information on the various sockets and plugs used around the world, visit World Wanders. These differences don’t change the basic design for creating a circuit to draw electricity from the grid. Throughout these different designs some fundamental components remain the same for most types of sockets.
Figure 2. A labelled diagram of a polarized two-pronged outlet.
Most outlets are polarized for safety. Polarized plugs can only be inserted into them one way (which seems annoying, but is actually an important safety feature). In North America, this is accomplished by having two differently sized slots in addition to the rounded grounding slot, the larger of which is called the neutral line, and the smaller called the hot line (see figure 2). The neutral is connected by a wire to ground, so its voltage is 0 V. Instead, the hot slot supplies the voltage required to draw current, and when a plug is inserted into the socket, the energy flows in from the hot slot, through the circuit, and ends at the neutral, which disperses the energy into the ground. Of course, to complete the circuit all the way back to the generator, the neutral is also connected back to the original distribution system in addition to being grounded at multiple locations. The benefit of polarization is that polarized plugs can only be inserted in one orientation, so the switch to turn any device connected to the socket on or off can be built into the hot lead. In a non-polarized plug, the switch may only open the circuit at the neutral lead, which means that most of the internal circuitry of the device is still considered “hot” and can lead to shock hazards.
Figure 3. A labelled three-pronged outlet.
Most modern sockets in North America have a grounding slot in addition to the hot and neutral(see figure 3). The grounding wire is connected much like the neutral, as it also connects to a grounded neutral tie block. The grounding slot is important for devices with a metallic casing or metal-cased power supply, like computers. If a hot wire in the internal circuitry of an electronic device frayed or somehow came into contact with a metallic casing, the entire device would then become a serious shock hazard. However, the grounding wire is directly connected to the casing of the device and will neutralize the risk of shock by diverting current to the ground, which will trip the circuit breaker, and stop the current flow to the device. Also, the ground prong will be longer than the neutral and hot prongs so that the device is grounded before it ever becomes “hot” or “live.”
Different Electrical Plug Types
Electrical plug types are different than electrical outlet types. While the electrical outlet is the jack, the electrical plug is what goes into the jack. The type of electrical plug varies by country according to World Standards.
While you may only see one or two types of electrical plugs in your lifetime, there are actually quite a few. Here is the majority of plugs sorted by the letter that represents them.
- Type A – this is the standard two-pronged plug from North America. It works with the standard outlets in North America as well and is generally 100-127 volt.
- Type B – this is the other type of American and Mexican plug. It has the two flat prongs on top but includes an extra grounded prong, giving in three prongs, the lower one being rounded. It is also 100 – 127 volt.
- Type C – this plug is common in Europe, South America, and Asia. It is the most common type of plug used internationally, is usually 220 – 240 V, and is insulated with two prongs.
- Type D – this is an Indian plug that is 220 – 240 volt in most cases. It has three round prongs with each prong being a different size so you know where to plug it in.
- Type E – this plug is used in France, Belgium, Poland, Slovakia, and Czechia. It has two rounded prongs and one very short ground prong that is located on the outlet.
- Type F – this plug is very similar to the Type E plug and it is used all over Europe. It doesn’t have the traditionally grounded prong but has two grounding tabs on top and bottom.
- Type G – this plug is used in the United Kingdom, Ireland, Malta, Malaysia, Singapore, and the Arabian Peninsula. It can be grounded or not grounded depending on whether the top prong is plastic or metal.
- Type H – this Israliean plug is used only in certain areas in Israel. They are 220 – 240 volt and have three close-together round prongs.
- Type I – another plug used in Australia, New Zealand, China, and Argentina, this plug has two slanged prongs and one round prong.
- Type J – this plug is primarily used only in Switzerland and Liechtenstein. It looks similar to the Type H plug but the top prongs are further apart.
- Type K – this electrical outlet type looks like the Type H plug as well but the bottom grounding prong has a flat top rather than round. It is found in Denmark and Greenland.
- Type L – this plug is used in Italy and Chile. It is around 230 volt like most international plugs but it looks very different. This plug has three round prongs all in a row vertically.
- Type M – this South African electrical outlet type has three rounded prongs with the top prong being larger than the other two. The plugs are usually shaped around the prongs.
- Type N – used in Brazil and South Africa, this type of plug comes in a lot of different power levels. You can find them anywhere from 100 volts to over 200 volts.
- Type O – this type of plug has three rounded prongs quite close together. It is hard to find this exact plug anywhere else except for in Thailand.