How We Know That Electric Kettle Switch Off?
Early small electric kettles had a built-in risk: it was relatively easy to turn them on, leave them on for a few minutes, and then forget about them. So don’t be afraid if you forget about electric kettle switch off while you are cooking.
If you were lucky, your kitchen would be filled with clouds of steam when you returned a few minutes later. Your kettle element could burn out, blow a fuse, or even start a fire if you’re unlucky.
Thankfully, almost all modern kettles use thermostats to the electric kettle switch off automatically (mechanical, electrical, or electronic devices that respond to changes in temperature). Many are based on designs created by John C. Taylor, an English inventor whose companies Otter Controls and Strix Ltd have produced over a billion thermostats of this type around the world.
How do they function? The most basic are mechanical, with a bimetallic thermostat integrated into the element unit at the bottom of the kettle (described in our main article on thermostats).
It’s made up of a disc made up of two different metals that are tightly bonded together, with one expanding faster than the other as the temperature rises. The bimetallic thermostat is normally curved in one direction, but when the hot water reaches boiling point, the steam produced causes it to snap and flex in the opposite direction, similar to an umbrella turning inside out in the wind.
When the thermostat opens, it pushes a lever that trips the circuit, cuts the electric current, and electric kettle switch off safely. More advanced kettle thermostats (found in systems like the trendy Marco Über coffee boiler) are entirely electronic, allowing water to be heated to precise temperatures and maintained indefinitely by repeatedly electric kettle switch off and on.
How Long Does a Kettle Take to Boil?
You can boil water in a variety of ways, including in a simple pan over an open fire or on a stove, but an enclosed kettle is usually faster because it prevents heat from escaping, allows pressure to rise faster (remember that water boils when its saturated vapor pressure equals atmospheric pressure), and speeds up the boiling process. But have you ever been annoyed by how long it takes your kettle to come to a boil? Don’t! The fact that your kettle boils so quickly is incredible—and here’s why.
If you keep pumping heat energy into the bottom of a kettle faster than it escapes through the top and sides, the water inside will boil sooner or later. The conservation of energy is a fundamental physics law that states that if you need to boil a liter of water at the same temperature, you must always add the same amount of energy. The amount of energy required to boil water is the same whether you use a campfire, a kettle, a microwave, or some amazing stirring device in the style of James Prescott Joule.
Let’s say you have 1 liter (roughly 1 kilogram, 2.2 lbs) of cold water at 10°C (50°F) that you want to heat to its boiling point (100°C or 212°F). You’ll need 4.2 1000 grams of energy at 90 degrees, which equals 378,000 joules (378 kJ).
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The mysterious “4.2” refers to the specific heat capacity of water, which is a constant value. Every material has a unique specific heat capacity, which is the amount of energy required to raise the temperature of one gram of the material by one degree Celsius. To raise the temperature of 1 gram of water by 1°C, you must add 4.2 joules of energy, so water’s specific heat capacity is 4.2 J/g/°C.