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I've noticed that the burners of some or all of the newish-style electric stoves which have a flat top have a peculiar property. They do not seem to be capable of running at a constant low temperature, instead periodically coming on high for brief-to-longer periods of time. These stoves were not, as I understand it, discount priced. They are not induction stoves, but seem to have an element embedded in the material which forms that part of the stove top.

Is this an across-the-board trend in new stoves? Is it difficult to find electric stoves which work the "old way", supplying a constant temperature? Is there an advantage to the way these newer stoves work? It would seem to be difficult or impossible to cook a range of dishes on such appliances.

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Just from an engineering point of view -- what you're calling 'binary' is often called a 'duty cycle'. (where the duty cycle can either describe the % time is spends on, or how long it stays on for a given time period) – Joe Mar 3 '11 at 13:21

The burners on essentially all electric stoves are binary in that they are either fully on, or fully off. It would be more expensive and less energy efficient to use electronics that continuously vary the current flow through an electric element, and this would make no significant difference in temperature behavior at the cooking surface. Instead, electric stoves use a bimetallic switch which is a relatively simple way to have an on-off pattern with variable on/off times. To create constant heat, all electric stoves use materials that are bad conductors of heat between the electric element and the cookware surface to buffer the huge temperature swings at the element and produce very steady heat at the cooking surface.

The difference you are seeing between electric coil heating elements and glass-ceramic cooktops is that in the electric coils there is an inner heating element, then a thick ceramic layer, followed by an outer layer of metal. The element itself is heated in a binary manner, but all you can observe is the heat after the buffering of the ceramic layer has made up for the large fluctuations at the element (i.e. the outer metal glowing fairly constantly once it's heated). In a glass-ceramic cooktop, since the buffer layer (the glass-ceramic surface) is translucent, you are seeing the actual element glow (often this is an infrared lamp instead of a resistive wire) so you are viewing the non-buffered heating pattern. If you had a clear coil, you'd see the same heating on/off patterns in a coil stove as you do in glass-ceramic.

Consequently, if you measure the surface temperature of a glass ceramic cooktop, you should see a fairly constant temperature.

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I don't think it'd actually be difficult (some power triacs should be able to do it, I believe), just more expensive & less efficient (more heat ejected into the room vs. the pot), and probably for no benefit since the temperature is already being averaged by thermal buffering. – derobert Mar 1 '11 at 17:08
Thanks for the explanation! I updated the answer to reflect this. – timmyp Mar 1 '11 at 18:19
This is quite informative. Is it possible that some newer stoves do not use adequate buffering? It seems that water boils harder when the elements/lamps/magic-red-circles are lit up. – intuited Mar 4 '11 at 5:26
That's possible. Another thing to consider is that since the surface is transparent, there is likely additional radiant heat when the element is on. I tried turning on my glass ceramic stove and almost immediately could feel heat a good 2-3 feet above the burner, so I think that pretty clearly means that there's a good bit of radiant heat that could cause the faster boil. It seems like they could easily solve this by just coating the bottom of the glass with black paint. I wonder if the additional radiant heat is desirable, or maybe the paint just wouldn't be aesthetically pleasing. – timmyp Mar 4 '11 at 18:35

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