| MadSci Network: Other |
I suspect the answer is pretty simple: stuff goes in the bottom, size of the element, and safety.
Anything you might put in the kettle is going to fall to the bottom (liquid, food stuff). If the heating element is at the bottom then the stuff inside is going to be closer to the heat and less heat will be lost heating the air.
The bottom allows the maker of the kettle to make a simpler and probably smaller heating element because it does not have to be the size of the diameter of the kettle. Typically, an electric heating element is simply a lot of wire wound up to occupy small space because the Joule heating goes as the power (Power = I^2 * R or Power = V * I, where I is current, V is voltage and R is resistance). More heat is produced with a higher resistance and less current is required for a fixed voltage, which makes the heating element safer for operation.
In most designs the handles are near the top, where the kettle is cooler because the heater is at the bottom. Remember, the kettle gets heated by the heating element, too. If the heating element is on the bottom, the hot spot of kettle is less likely to be touched by person using the kettle.
Some other related answers
Re: What causes incandescence/Joule heating: electronic or ionic movement?
Re: Are heating elements made of high resistance materials?
Re: why does styrofoam work in coolers and coffee cups?
Sincerely,
Tom "I don't cook" Cull
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