Most mornings you get out of bed and stroll over to the kitchen.
You switch on the kettle and while you wait for it to boil, you just stare at it.
And then you start wondering….
Why does it take so long?
Can’t I make it go faster?
How does an electric kettle work?
Well, if you read this article, you won’t need to wonder anymore.
So keep on reading!
In this article I will discuss:
Introduction
To boil water is probably one of the most primary functions in any kitchen.
Humans have been doing it for ages and and it serves several purposes. Two of the main ones is to cook food and to sterilize water.
A third reason, more so in modern times, is to brew coffee and tea.
Which brings us to the modest electric kettle. A jug that turns an age old process lasting probably more than an hour into mere minutes.
To be more exact, it takes a 2400 watt kettle on average 160 seconds to boil 1 litre of water.
The first kettles were steam kettles, also called the whistling kettles.
They were called that because these cooktop kettles would start whistling when they started to boil.
That was due to steam buildup in the kettle once it started to boil, and that steam would vent through a whistle on the spout or lid.
It was in 1922 when these were replaced by electric kettles invented by Arthur Leslie.
How an electric kettle heats up water
So how does an electrical kettle work?
Let’s start off with the science part of it all.
Any electrical conductor, which is a material that conducts electricity, has resistance.
Resistance is a measure of how difficult it is for electrical current to flow through a conductor.
Copper has a lower resistance and is therefore really good at conducting electricity.
Porcelain, on the other hand, does not conduct electricity because of its very high resistance.
In most cases when a current flows through a material with resistance, heat is generated.
It is on this principle that an electrical heating element works.
The element has a high resistance and when an electrical current flows through it, heat is generated.
The element of a kettle sits at it’s base. It will either be a visible metal coil inside the kettle just above the bottom, or a hidden element built into the base.
When an electrical current flows through the element, it heats up. That, in turn, heats up the water around the element.
The warmer water rises up and the colder water sinks to the bottom where it gets heated up as well.
This circulation continues as the water gets warmer and warmer until is boils.
Limescale buildup in your kettle, especially around the element, can cause the kettle to work less efficiently.
If you have limescale buildup, read here how to descale your kettle.
What is a thermostat?
Most modern electric kettles are equipped with an auto shut off mechanism called a thermostat.
These mechanisms automatically switches off the kettle when it boils.
A standard thermostat is a device that can disconnect and reconnect the power supply depending on temperature. You will find one in almost any appliance and system that is temperature regulated.
Examples include air conditioners, refrigerators, central heating systems and ovens.
It works by using a bimetallic disc or rod. It is two different types of metals joined together.
The one metal expands much faster than the other when exposed to higher temperatures.
That causes the the disc or rod to bend. It is this bending movement that can act as an electrical switch when built into an electrical circuit.
Why does water boil?
Water boils at different temperatures depending on several factors, the main one being altitude.
At sea level water boils at exactly 212 degrees Fahrenheit, or 100 degrees Celsius. The higher the altitude, the lower the boiling temperature.
It has to do with air pressure. A liquid boils because the liquid is starting to turn into a gas when sufficient heat is applied for long enough.
The bubbles you see is the air escaping from the liquid into the atmosphere.
The higher the air pressure, the harder it is for the liquid to turn into a gas, and vice versa.
How does an electric kettle switch itself off when it boils?
Due to the above an electric kettle would not work with a standard thermostat monitoring the water temperature in the kettle.
That’s why a kettle’s thermostat is not triggered by water temperature, but by air temperature.
There is an air tube that runs from the top of the kettle to the bottom. The inlet is at the top and at the bottom it ends at the thermostat.
When the water in the kettle starts to boil, steam is formed.
The lid of the kettle causes pressure to build up. This pressure forces the steam into and down the air tube to the thermostat.
The steam causes a sudden rise in temperature at the thermostat and this is what causes the thermostat to cut the power to the heating element.
With this mechanism it does not matter at what temperature the water boils because the temperature of the steam is enough to trigger the thermostat.
Conclusion
And that is how an electric kettle works. How it boils water and how it switches itself of.
It is surprising what goes into something as simple as boiling water!
Next time you stare at the kettle wondering if it can go any faster, you’ll know.
And if you’re on the lookout for a kettle, check out my list of the best selling kettles here!