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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.
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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.
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