So I went out to get a new kettle a few days ago. I’ve now given up on a rather lovely design by the company Chantal that I’ve been using for many years since on two models in succession (or is it three?) the same flaw has revealed itself – the plastic parts of the Hohner whistling lid began to loosen gradually (probably from too much heat up the sides, which may be my fault) and then you eventually end up with a non-fitting non-whistling lid.
I began to assess other kettle designs, and in doing so found myself thinking idly about a number of physics issues. One of the main ones was energy. If I got a smaller kettle (the one I had before had a capacity of 1.8 quarts, and I was considering ones as big as 2 quarts and ones as small as 1.5 quarts), which I was leaning heavily toward, it would probably encourage me to save energy and not boil so much water. On the other hand, maybe that’s really silly, since I might just be putting the same amount of water into the kettle anyway… I’d never fill either up all the way in any case. But if I put the same amount of water into both kettles, would the smaller one end up using less energy anyway as I don’t have to heat up the extra air in the chamber, or does that not matter…? It’s not that simple since the chamber is not sealed. Hot air (and later, steam) is escaping all the time. Well, this is all complicated by the fact that the smaller kettle has less of its base in contact with flame, so I’d have to turn down the flame, and heat it for longer on a lower flame than with the larger kettle… would that make a difference? Perhaps a smaller chamber at lower flame means slower steam escape velocity, and so a quieter whistle. Not good if you’re prone to forgetting that you’ve put the kettle on during an absorbing computation…downright dangerous, in fact!
This was not an entirely serious discussion, you see, but it’s sort of fun sometimes to find these things floating around in one’s head. Physicists (and I imagine, other scientists) have this sort of thing flit through their heads a lot. The key thing -especially as a Theoretical Physicist- is knowing when to engage with one of these problems, and when to ignore them. Is there are clear route to tackling the problem? Is it worth it? Is there something to be learned from solving this problem that might be useful elsewhere? In fact, I was trying to explain this all to a writer friend of mine Continue reading ‘Consider a Spherical…’