How Does The Switching System Turn Off An Electric Kettle When It Boils?

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Curnow

asked 3 years ago

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it has a thermostat which only reaches a certain temperature.

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Leisa

answered 3 years ago

A simple thermostat would not sense when the water boils. Water temperature rises to 100DegC (depends on atmospheric pressure) then needs to absorb a lot more BTU's before it boils but still remains at 100DegC. A normal thermostat is only capable of sensing temperature not boiling point. So the question remains, How does the switch sense boiling point and turn the kettle off?

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Curnow

commented 3 years ago

The thermostat works because it does not measure the water temperature, but when it detects steam. A small tube ducts steam to the thermostat only when the water boils and pressurizes the chamber. Hence if you leave the kettle lid off, it won't switch off.

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Kingsrd

commented 1 year ago

Sorry, Kingsrd, but 95% of kettle works on a simple thermostat. And even if it looks they should not work, they can work correctly, if heater is at the bottom of the kettle. Why? Because when water boils, water keeps it's boiling point, but steam temperature can rise. When steam bubbles are produced on heating element, heat conduction rapidly drops (that's why ice cube or water drop is "dancing" on a very hot surface instead of just quickly vaporize). When heat transfer drops rapidly, and power supplied to the heating element is constant, the temperature of heating element rises rapidly. Thous, if thermostat is set to 102 Celcius degree, it will switch off even in mountains, when boiling temperature is lower.