2007-09-12 10:23:59 · 13 answers · asked by boyinlove2k 2 in Home & Garden ➔ Maintenance & Repairs
It is true that there is a bi-metallic switch, which switches off when it boils, as the switch is made from two layers of different metals, which expand at different rates when heated, which causes the sandwich of the two metals to "bend" when it heats up.
However, the switch is not sensitive enought to know the difference between almost boiling and boiling.
To overcome this therefore, the switch does not actually measure the water temperature.
What happens is that when the water boils, some of the steam is channelled through a part of the kettle where the switch is placed. There is no water there, as this channel in the kettle leads out to the outside air.
Hence the switch can be set to operate at a wide range of temperatures (say anywhere between 80degrees and 100degrees), because only when the kettle actually boils does the steam get produced and travel along the cavity in the kettle that contains the switch.
So the switch only "knows" that there's hot steam flowing around it, it does not "know" what the temperature of the water in the kettle is.
This makes for a cheaper (less sensitive and accurate) switch, and it ensures the kettle only switches off when it is really boiling, not just hot.
2007-09-12 22:54:58 · answer #1 · answered by Valmiki 4 · 0⤊ 0⤋
There's a temperature sensor inside the kettle.
Water boils at 100 degrees C, when the water reaches that temperature, the sensor switches the kettle off.
2007-09-12 10:27:33 · answer #2 · answered by Al 4 · 0⤊ 2⤋
Don't try to use your kettle at high altitudes.
The mechanism is a temperature limit switch, but water boils at lower temperatures at higher altitudes.
Actually, I have never seen an open kettle with that type of switch.100 deg. C. is the boiling point of pure water at sea level at standard conditions. A situation that rarely exists in nature. Due to variations in boiling points, that mechanism would be unreliable, and a truly accurate temperature limit switch is very expensive, so I doubt it would be installed in a commercial pot.
If the kettle has a sealed lid that would permit an increase in pressure when the water starts to boil, a more reliable control would be possible.
A typical coffee maker forces the water out of a reservoir and when the water is gone from the reservoir, the temperature rises rapidly, allowing the temperature limit switch to trip off, interrupting power to the heater before damage can occur.
2007-09-12 10:38:20 · answer #3 · answered by Philip H 7 · 0⤊ 3⤋
There is a little Genie inside who switches the kettle off when the water gets too hot for him!
2007-09-13 04:55:34 · answer #4 · answered by jacyinbg 4 · 0⤊ 0⤋
There are 2 different metals on a strip which buckle in the steam, and for the benefit of " philip H " was invented by a Brit called Russell Hobb.
Their company intend exporting to the USA soon.
2007-09-12 12:05:32 · answer #5 · answered by xenon 6 · 0⤊ 0⤋
A bi-metallic switch in the circuit physically bends at 100degC and so switches it off.
2007-09-12 10:26:42 · answer #6 · answered by ? 7 · 0⤊ 0⤋
I guess because it's smarter then me. I don't know how, but the kettle does. Kiss kiss
2007-09-12 10:27:27 · answer #7 · answered by Anonymous · 1⤊ 0⤋
it has a thermostat, once it reached the temperature it switches off
2007-09-12 10:28:33 · answer #8 · answered by versace_girl_2002 3 · 0⤊ 0⤋
kettles are male - they know everything
2007-09-12 10:27:44 · answer #9 · answered by Anonymous · 3⤊ 0⤋
Well done Zenon short,sweet & correct answer
2007-09-12 20:05:57 · answer #10 · answered by Anonymous · 0⤊ 0⤋