Teakettles come mainly in two different varieties. There is the electric kettles which use electricity to boil water. Once the water has boiled the kettle deactivates to stop the water boiling away and to protect the kettle. The other are metal kettles which boil water when heated using a stove. These kettles usaully have a whistle indicating when the water has boiled. Before the invention of electirc kettles these kettles where the norm.
