Quick history of design of kettles:

In the early 1800s, fire was used to heat up liquids. First electric kettle is said to be discovered in 1891. In that design the heating element was in a different compartment than the liquid itself, and hence it took longer to heat the liquid. This issue was solved around the 1920s, when the heating element was placed inside a metallic cylinder, which was placed directly within the liquid. The vessel containing the liquid used to be made of iron initially, but later was replaced by copper due to it’s higher thermal conductivity. The early 1900s was the period of the whistling kettles, which used noise made by steam passing through a tiny aperture as an indication that the liquid has heated enough. If you want to know more about what principles of fluid dynamics govern the whistling noise, visit this wikipedia article. One interesting thing about the innovation of whistling kettles is that the design and usage came way before a proper reasoning for its working could be established within the scientific community. Read this news piece to know more about the innovation of the same. Today, most kettles make use of resistance elements to convert electrical energy found in our homes to thermal energy used for heating. Moreover, most of them use differential heat expansion of metals for ‘cut-off’ feature that ensures the device switches off once water reaches its boiling point. This makes the device less prone to accidents and more user-friendly.

For more information on:

1. Another design, view this article on closed loop design by guardian.
2. Another nice article about functioning of a kettle.

-x-x-x-x-x-x-x-x-x-x-x-x-x-x-