How do electric kettles work? - Explain that Stuff

Electric kettles Cars run on gasoline... and people run on tea and coffee (at least in my house)! If you drink coffee or tea by the bucket, you'll be glad someone once had the gumption to invent a super-efficient way of turning cold water into hot— namely, the electric kettle (also known as an electric tea kettle). Fill it with water, plug it in, switch it on, and in a couple of minutes you have piping hot water ready for drinking or cooking. How exactly does a kettle work? Why does it take so long to boil? And how does it know when to switch itself off?

Let's take a closer look!

What is an electric kettle?

K

ettles are among the simplest of

household appliances. Lift the lid and peer inside and you'll see, at the very bottom of the water container, a coil of thick metal called the heating element flows into the

heating element. The element's resistance (the tendency any material has to stop electricity flowing through it) turns the electrical energy into heat. In other words, the element gets hot. Since it's in direct contact with cold water, the heat passes to the water by conduction and rapidly warms it up too.

How do instant hot water boilers work?

If you're tired of waiting and you want your kettle to boil faster, there are only two things you can do. One is to use more electric current—in other words, buy a more powerful kettle; the other use is to use less water.

"Instant" water boilers/dispensers (such as the Beeville Hot Cup and the Murphy Richards Meno), which can boil as little as a cupful of water really quickly, combine these methods.

They use a more powerful heating element than an ordinary kettle (typically 3000 watts or more) and they're designed so the element can operate safely in contact with only a small amount of water. If you're boiling only (say) a quarter of a liter of water, you need only a quarter as much energy—say 100,000 joules. And if you're supplying that energy with a 3000-watt element, do the math and you'll find you can do it in about 30 seconds instead of 2.5 minutes.

Can you see another great benefit here? If you're boiling an entire kettle to make just a single hot drink, you're effectively wasting three quarters of the energy you're consuming. Boiling only as much water as you need saves you a significant amount of money—and helps the environment too.