[annabelt]

Ok here's a small scientific question...

I was at my friend's house and made some tea, and they were annoyed that I filled up the kettle too much because it wastes energy boiling more water than you need. They will generally fill it up a little bit each time and use the whole lot. But when I'm at home I drink so much tea that I tend to fill up the kettle in the morning, boil the whole thing, and then each time I go back for another cup it's still hot and boils very quickly (plus I don't have to drink the flaky bits at the bottom). Ok most people are probably thinking 'just don't drink so much tea', but I wondered if there is a point reached in excessive tea drinking when it's more energy efficient to fill the kettle. Differential equations maybe?