Electricity passes through the kettle element, as it passes through the metal element provides resistance to the electrical flow. This resistance dissipates energy which is dissipated in the form of heat. The heat is passed from the element to boil the water.
Kettles have an element at the bottom, which is heated up by the electric current connnected to it. As the current flows through the plug and the connection, the element becomes extremely hot and disperses the heat throughout the water, at this stage you see tiny bubbles rising from the element. After a minute or so, the water reaches boiling point, starts to agitate, and the steam comes out of the spout of the kettle. If you have a whistling kettle, this is when the steam is forced through a small hole, causing the whistling sound the kettle makes when the steam goes through it. Now you are ready to make that cup of tea.
