# Mircrowaves, a stupid question **URL:** \ **Category:** Factual Questions\ **Created:** [September 26, 2001, 12:52am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831 "2001-09-26T00:52:40Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Samui](https://avatars.discourse-cdn.com/v4/letter/s/41988e/32.png) [@Samui](https://boards.straightdope.com/u/Samui)\ **Post date:** [September 26, 2001, 12:52am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/1 "2001-09-26T00:52:40Z")
Why do microwave turntables switch directions each time they’re turned on? ---
**Author:** ![ski](https://avatars.discourse-cdn.com/v4/letter/s/bbe5ce/32.png) [@ski](https://boards.straightdope.com/u/ski)\ **Post date:** [September 26, 2001, 1:19am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/2 "2001-09-26T01:19:45Z")
They don’t. You’re just forgetting which way it turned the last time. 🙂 Actually, this is microwave specific, yours just does it because for whatever reason the designers made it that way. I’ve actually never seen one that does this. Most I’ve seen only turn one way, or do not have a turntable at all. This latter type seems to be getting more popular. (Less moving parts to fix, I guess) ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [September 26, 2001, 1:57am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/3 "2001-09-26T01:57:34Z")
My GE Spacemaker XL switches rotation direction, too. ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [September 26, 2001, 2:00am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/4 "2001-09-26T02:00:29Z")
Just a WAG that some engineer figured out that this would somehow extend the service life of some part or parts involved in the rotation. ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [September 26, 2001, 2:18am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/5 "2001-09-26T02:18:49Z")
The hampsters are much more motivated if they don’t have to run on the wheel the same direction all the time. Thus microwaves with bi-rotational turntables, automobiles with forward and reverse gears, and the space shuttle which goes way out there and then returns. ---
**Author:** ![Samui](https://avatars.discourse-cdn.com/v4/letter/s/41988e/32.png) [@Samui](https://boards.straightdope.com/u/Samui)\ **Post date:** [September 26, 2001, 6:40am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/6 "2001-09-26T06:40:10Z")
c’mon guys… Is that the best you can do? I thought this was the famous straight dope message board. I gotta confess, I’m a little disapointed. ---
**Author:** ![puk](https://avatars.discourse-cdn.com/v4/letter/p/ea5d25/32.png) [@puk](https://boards.straightdope.com/u/puk)\ **Post date:** [September 26, 2001, 7:16am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/7 "2001-09-26T07:16:39Z")
It’s the AC man! It’s allways the AC. The AC will get you… eventualy ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [September 26, 2001, 8:04am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/8 "2001-09-26T08:04:26Z")
Welcome to the board **Samui**. Looking for why a microwave turntable changes direction is not a great subject of interest for many dopers. Now, asking why grapes sparkle in the microwave? That is more like it! : [http://www.geocities.com/Tokyo/Temple/3717/Geeks/eegrape.htm](http://www.geocities.com/Tokyo/Temple/3717/Geeks/eegrape.htm) 😃 Seriously, I think the switch of direction is done to ensure that the food will be evenly cooked: From a new Sharp microwave manual: “The turntable in the oven reverses direction. Is this normal? Yes. The turntable reverses direction at random intervals.” [http://rabi.phys.virginia.edu/HTW/microwave\_ovens.html](http://rabi.phys.virginia.edu/HTW/microwave_ovens.html) > [@](#): > > As the microwaves bounce around the inside of the cooking chamber, they tend to interfere with one another. There are usually regions in which the waves that follow various paths almost cancel one another and regions in which the waves reinforce one another. These regions don’t cook food equally well. If the microwaves are canceled in one region, cooking will be slow there. If the microwaves reinforce one another in another region, cooking will be fast there. If you simply leave food in one place and try to cook it in the microwaves, the cooking will be uneven. However, if the food is rotated continuously, these good and bad cooking regions will be blurred away so that the food will all cook at about the same speed. ---
**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\ **Post date:** [September 26, 2001, 10:59am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/9 "2001-09-26T10:59:39Z")
Come on guys! This is a serious question, and as such requires a serious answer. > [@](#): > > \*Originally posted by Samui \* > \*\*Why do microwave turntables switch directions each time they’re turned on? \*\* It’s becouse the cheapest single phase electromotor that can be had is the **synchronous two-pole** motor. The initial direction of rotation depends on the position of the rotor within the electric field, which for all practical purposes is rando,. Thus the perceived randomeness of the rotation. For a brief description of how an electric motor works, look at [HowStuffWorks](http://www.howstuffworks.com/motor.htm) But I guess that’s what **puk** meant as well. ---
**Author:** ![puk](https://avatars.discourse-cdn.com/v4/letter/p/ea5d25/32.png) [@puk](https://boards.straightdope.com/u/puk)\ **Post date:** [September 26, 2001, 11:55am UTC](https://boards.straightdope.com/t/mircrowaves-a-stupid-question/83831/10 "2001-09-26T11:55:23Z")
actually, I found the same link you did, but wasn’t sure this guy was serious or not. Guess I didn’t want to get baited 😃