I’ve always believed that whatever you’re cooking or heating up should be placed at the centre of the rotating microwave plate. I can’t really offer any rational reason for that belief except that it’s the centre and the centre is better. It appeals to symmetry, I guess. I doubt that microwaves converge in an oven, but if they did, the central part of the plate would be the logical point of convergence. So place stuff right in the middle, is my point of view.
My husband, on the other hand, thinks stuff should be placed somewhere between the centre and edge. He has no specific reasons for this belief, except that he just thinks that’s how it should be. This bugs me because it’s not symmetrical, dammit.
I always use the edge if I can. Works good for Hot Pockets, and I notice more heat in the pocket when cooked on the edge than in the center. If heat a plate of food, I’ll put it on the edge too. Sounds like an easy theory to test out, assuming all micros wave the same.
If you place the items (i.e., the weight) in the center, the motor that makes the tray rotate will last longer. Think of it this way: would you rather carry a child on your shoulder or on your shoulderS? Having the weight so that its center of gravity is on the same vertical as yours is better for you and it’s better for the tray’s motor.
As for the waves themselves, it doesn’t really matter: the purpose of the rotating tray is to make the dish get as uniform a “shower” as possible.
That depends on individual construction- most microwaves of my acquaintance have rollers or other bearing on the platter periphery which negate cantilever on the motor (or axle) axis.
It probably depends on the microwave, but in general I think your husband has it right (us husbands always do ;)).
The problem with nukers is that they tend to heat unevenly. They have “hot” and “cold” spots (not really hot and cold, but places with more/less concentration of microwaves). If you put something other than in the centre, it will travel through a greater range of places in the microwave. I always place things as far towards the outer edge as possible, so that they rotate in the biggest loop around the interior possible. If you put something in the centre, it is only rotating on the spot.
In the ideal case, the energy would be uniformly distributed in the oven cavity and it would not matter squat where you placed the food or how you oriented the container.
The very existence of turntables in microwave ovens is proof that the ideal isn’t achieved. The purpose of the turntable is to move the food so even though the oven has hot & cold spots, you won’t end up with a dish sitting in a cold spot, or half in one, throughout the cooking cycle. IOW, moving the food around inside the oven has the effect of averaging out the inevitable hot & cold spots.
Now consider placing a circular bowl dead center on the turntable. The only averaging you’re doing is within that small area as the bowl rotates without visiting all the areas of the oven. in other words, you’re removing about 70-85% of the effectiveness of the turntable since yuo’re sweeping out a much smaller footprint per rotation.
They do NOT design the oven to have a hotspot in the middle. That’d be too dangerous. As well as ensuring that any large dish placed in there would cook unevenly, turntable or no.
Bottom line: In general, the best placement is whatever makes the dish cover the most surface of the oven floor during a single rotation of the turntable. IOW, the opposite of placing your dish dead center.
Caveat: Oven models, and even ovens, are individual. An easy experiment is to take out the turntable & cover the entire floor of the oven as best you can with small bowls of water. Tea lights or shot glasses work great, as do small ramekins.
Fill each with 1/2" of water. Start the oven on high for, say, 5 minutes. While it works, watch the glasses & see which ones boil first. You’ll probably find some are boiling long before the others. The very corners may never boil. And you probably won’t find the first-to-boil at the center.
ETA: Gotta type faster or say less. Thanks Princhester for saying it all much more succinctly than I.
I’ve always placed items as far toward the outside as possible for the same reasons stated above; dead center doesn’t move anything around, just rotates it, which doesn’t do much good if the center is a bit of a cold spot. Better to have whatever you’re nuking getting the grand tour. It certainly doesn’t hurt, unless symmetry is really important to you.
Having the load offcenter will place slightly more stress on the output bearing, but the motor and the gears it drives the load through won’t care a bit. As noted, most turntables have the turntable supported by rollers; those which don’t are usually found in small ovens. In any case, even given some bearing wear (which in turntable motors tend to be more robust sleeve bearings, as opposed to ball bearings), the worst you can expect is some very slight play in the shaft. At the low output speed of 6 RPM in US ovens, this is entirely negligible. If it breaks anyway, well, that’s more likely a consequence of buying a $29.99 oven at Costco than from “improper” turntable loading.