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The Problem with Microwaving Tea:
Typically, when a liquid is being warmed, the heating source — a stove, for example — heats the container from below. By a process called convection, as the liquid toward the bottom of the container warms up, it becomes less dense and moves to the top, allowing a cooler section of the liquid to contact the source. This ultimately results in a uniform temperature throughout the glass.
Inside a microwave, however, the electric field acting as the heating source exists everywhere. Because the entire glass itself is also warming up, the convection process does not occur, and the liquid at the top of the container ends up being much hotter than the liquid at the bottom.
A team of researchers from the University of Electronic Science & Technology of China studied this nonuniform heating behavior and presents a solution to this common problem in the journal AIP Advances, from AIP Publishing.
By designing a silver plating to go along the rim of a glass, the group was able to shield the effects of the microwave at the surface of the liquid. The silver acts as a guide for the waves, reducing the electric field at the top and effectively blocking the heating. This creates a convection process similar to traditional approaches, resulting in a more uniform temperature.
Placing silver in the microwave may seem like a dangerous idea, but similar metal structures with finely tuned geometry to avoid ignition have already been safely used for microwave steam pots and rice cookers.
Journal Reference:
Peiyang Zhao, Weiwei Gan, Chuanqi Feng, et al. Multiphysics analysis for unusual heat convection in microwave heating liquid [open], AIP Advances (DOI: 10.1063/5.0013295)
(Score: 2, Touché) by Anonymous Coward on Wednesday August 05 2020, @10:53PM (2 children)
If somebody doesn't already know how to do that, the correct way to instruct them is to say "Hire an electrician."
(Score: 2) by drussell on Thursday August 06 2020, @02:09PM (1 child)
Obviously if you aren't competent or comfortable doing a particular job, especially something like electrical work, you should hire a professional to do the job. (hopefully, correctly!) You need to at least know that something is possible, though, before you can ask said professional to do some particular thing for you.
My point was simply that you CAN get a "proper" 3000W 240v kettle and have a proper, safe, valid plug for it in your kitchen. The same plug also works for things like one of those small countertop-sized commercial deep fryers if you're tired of attempting to make your wings and fries or fish or whatever in tiny batches in a wimpy little 1500W residential joke of a deep fryer.
Believe me, I've seen my fair share of scary electrical work, even relatively simple things like changing a plug, that were obviously done by clueless homeowners or handymen. On one renovation we did many years ago, someone had changed all the plugs on the main floor of the home, and only two of the plugs were even wired with the correct polarity. The other 20 or so were all wired with the hot and neutral reversed. Egads!
If you don't know what you're doing, hire a professional! :)
(Score: 0) by Anonymous Coward on Thursday August 06 2020, @10:30PM
When you get to the point of instructing what color tape to put on exposed wires, you are a bit past "it's easy and fairly cheap to get 240 volts in your kitchen, an electrician can do it in a few minutes".