How do kettles boil water?

The electric kettle works thanks to two design breakthroughs achieved in Britain in the Twenties and Thirties. The fi rst is the immersed heating resistor, the piece of technology responsible for actually heating the water in the kettle. Resistors, which take the form of the heating element in the bottom of the kettle, work by resisting the fl ow of electric current passed through them, creating resistance and consequently heat. This heat is then passed into the water, which is subsequently heated up. The second of these advances allowed for an automatic cut-off point, preventing the kettle from perpetually heating up the water. A bimetallic strip was introduced to the electric kettle by Russell Hobbs in 1955 which when heated by steam expanded, triggering a shut-off switch. Although some kettles have fancier and more complex heating and shut-off designs, it is through these two basic principles that the electric kettle evolved into the appliance we have in our kitchens today.