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Kettles are vessels for heating water, by using electricity, or gas, or fire. Generally considered as a kitchen appliance, the hot water being typically used for making tea, coffee, etc. In areas where the tap water is hard water, kettles eventually become encrusted with scale (sometimes referred to as "fur", as a kettle may be stated to have become "furred up"), and this can be fixed by kettle descaler

A kettle may be termed a water 'otter as if it is some kind of furry critter.

"A whole different kettle of fish" refers to fish kettles, which are different from the type of kettles used for making tea. A fish kettle is a flat utensil which can contain a full-length fish for boiling.

"The pot calling the kettle black" is an old-fashioned expression where an accusation is arguably equally applicable to the person doing the accusing as it is to the person they are accusing. This dates back to the time when cooking pots and kettles were iron vessels heated on open fires, and would be equally covered in soot as each other!

The tradition of heating such items on fires still continues in some places for various good reasons including saving money on electricity, as practised by an aunt I knew.

The amount of energy required to heat water is one KCal per litre for every degree Celsius temperature rise. A KiloCalorie is 4186.8 Joules. As a Watt is a Joule per second, and a kilowatt-hour is 3.6 million Joules, it is easy to calculate that the energy required to heat two litres of water from 20 degrees C up to 100 degrees C is about a fifth of a kilowatt-hour, which costs about a penny GB or two cents US, or to put it another way, "not a lot".

If the power of the kettle element is 2.5 kilowatts, it should in theory take 268 seconds to finish, which is about right in comparison to experimental observation.

Heating basic non-electrical kettles on the gas is another method used, but electric kettles have the advantage of automatically switching off. In contrast, stainless steel or aluminium kettles on a cooker ring are sometimes forgotten and then they can boil dry. I have even heard of a case of this where the aluminium kettle boiled dry and then the metal melted into the cooker. The owner, who was a very clever but absent-minded inventor, on discovering this oversight, immediately turned off the cooker and left it to cool down, but was later dismayed to find the remains of the melted kettle had now solidified in amongst the workings of the cooker, and this could only be released by turning the cooker back on again to re-melt the kettle!

Usually, expressions such as "Has the kettle boiled yet?" refer to the condition of the water in the kettle and don't expect replies such as "No, it's only just melted!".

Another thing NOT to do to a kettle, is the addition of one spoonful of milk to the water in the kettle before boiling. Although this may seem an insignificant amount of milk to add to several litres of water, the result is quite striking. An electric kettle mistreated in such a way will fail to switch off upon reaching boiling point, and the water is altered by the milk in the way it boils, and so will gush out of the spout and make a terrible mess.

It has been speculated that it may be possible to apply custom car style techniques to the building of kettles, to produce a "suped-up" GT extra high powered kettle which, in a "0-60 in so-many seconds" sense, can boil so-many litres of water in an impressively short time. The main problem to doing this is the power supply abilities of domestic electric sockets, (in the UK the limit is 13 amps at 240 volts, giving a theoretical maximum power of 3120 watts). One possible suggested way to overcome this is to construct a Custom Kettle with three (or six) elements, and power it with an industrial three-phase power outlet. Another idea, moving into the realm of extreme custom kettling, is to have an arbitrarily large kettle element array with a circulator pump, and to power it from twenty car batteries connected up in series under the kitchen units. Even if they were small car batteries this would still provide 150 amps at 240 volts, giving an effective output of 36 thousand watts. It would also be even more dangerous than expected, as it's DC*

Atomic powered kettles are also a possibility, although there are various safety and environmental issues. The NERVA spacecraft engine is such a thing.

Other references: Space, electrical shops, science, cups of tea, etc.

* RISK: Well, at high voltages, DC is more dangerous than AC because the switchgear has to cope with DC being more difficult to switch off than AC, and there is a bigger risk of arc and fire. However, there has always been a lot of fuss about whether DC or AC is more Dangerous. The fact is that from the electrocution risk, there is much less evidence than rumour and speculation, and unless there is something more evidence-based coming in to show facts scientifically, both AC and DC are assumed to be equally dangerous.