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Datum: 25. 5. 2012 Projekt OBOGATENO UČENJE TUJIH JEZIKOV Primer PRIPRAVE NA POUK tujega jezika za mesec MAJ 2012 Priloga 2 Šola: Status šole: Naslov priloge: Kratek opis (vrsta in vsebina): Ciljni tuji jezik(i): CIRIUS-Kamnik partnerska šola Mains Electricity Around the World Reading Comprehension Text Besedilo angleščina Operacijo delno financira Evropska unija iz Evropskega socialnega sklada ter Ministrstvo za šolstvo in šport. Operacija se izvaja v okviru Operativnega programa razvoja človeških virov v obdobju 2007-2013, razvojne prioritete: Razvoj človeških virov in vseživljenjsko učenje; prednostne usmeritve: Izboljšanje kakovosti in učinkovitosti sistemov izobraževanja in usposabljanja. Reading Comprehension Text Mains Electricity What standards exist? There are two main standards of mains power systems in use worldwide: the North American and the European standards. Each standard differs in the voltage, frequency and plug/socket arrangement that it uses. Standard Voltage (V) Frequency (Hz) Plug and socket type North American 120 60 A&B European 220 – 240 50 C-M Other countries on different continents have adopted either standard or a mixture of each standard. In some places, like Hong Kong, they use the same voltage as China, but British-style plugs and sockets (this is due to Hong Kong’s former status as a British territory). What are power plugs and sockets? Power plugs and sockets are devices designed to provide a relatively safe method for attaching appliances to a power source. Because a power plug is inserted into the power socket, a power plug is usually referred to as being 'male' whilst the power socket is 'female'. A power plug completes the circuit between power plug power socket the power source and the appliance by feeding power into the appliance (via the 'live' pin) and drawing unused power back to the power source (via the 'neutral' pin). Both 2-pin and 3-pin power plugs function in this manner. In a 3-pin plug, the additional pin is the 'earth'; it connects the appliance to the building's earth ground as a protection against faults. Smaller electrical appliances like hair-dryers usually only have a 2-pin plug because they are already 'double-insulated'; they have 2 layers which encase the live parts and prevent electric shock. To be polarised or unpolarised? Power plugs can be either polarised or unpolarised. If you look at an Australian plug, there is only one way it can be plugged-into the power socket – it is an example of a polarised plug as the live and neutral conductors of the socket are connected to their respective poles of the appliance. Europlug socket Australian socket Conversely, if you look at a 'Euro' plug, it can be plugged into the power socket either way, so the live and neutral wires are connected arbitrarily. This plug type is unpolarised and can result in some appliances, like toasters, remaining live, even when switched-off. Therefore, you need to be careful when plugging in unpolarised plugs. 2 What are fuses and circuit breakers? A fuse is a protection device which blows (melts) when too much current flows through it, thus interrupting and preventing further damage to an electrical circuit caused by overload or short circuit. But, nowadays, fuses are rarely used with mains power since a blown fuse needs to be replaced manually. In most countries, fuses have now been replaced by circuit breakers. circuit breaker fuse A circuit breaker has the advantage that unlike a fuse which operates once and has to be replaced, it can be reset (either manually or automatically) to resume normal operation. A house's circuit breaker box contains all of the household's circuit breakers (for example, lights, stove, hot water etc.) How does mains power affect the travelling public? Before the advent of low-cost international air travel, the development of divergent mains power systems was not problematic since people did not travel. However, nowadays, most travellers take a plethora of electronic devices with 'Euro' plug them like laptop computers, cameras, mp3 players and mobile phones. So, the simple task of recharging your laptop computer is now complicated because your electrical power plug can be of a different type from the local standard. Whilst this is not an issue across continental Europe due its use of the 'Euro' plug, it is a problem if you travel, for example, from Slovenia to Canada. Some examples of different systems are summarised below. Country Australia Canada United Kingdom Voltage (V) 240 120 230 Plug / Socket Some countries, like Australia, also utilise a switch as an additional level of safety. Adapters Fortunately, travellers are now able to purchase travel adapters which can easily allow the interconnection of normally-incompatible plugs and sockets. Adapter However, travel adapters do not solve the problem of incompatible voltages, like when you try to use a laptop with a European power supply in the USA. In these situations, a voltage converter must be used. Usually, when you purchase a voltage converter, it also includes the required adapter. Adapter (with voltage converter) Furthermore, a voltage converter doesn't change the mains frequency; this could result in overheating of equipment which is designed for a different frequency, even just a 10 Hz difference is significant. 3