# Microwave ovens **URL:** \ **Category:** Factual Questions\ **Created:** [November 30, 2003, 7:28pm UTC](https://boards.straightdope.com/t/microwave-ovens/216094 "2003-11-30T19:28:00Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [November 30, 2003, 7:28pm UTC](https://boards.straightdope.com/t/microwave-ovens/216094/1 "2003-11-30T19:28:00Z")
Every time I use my microwave oven the turntable spins the opposite direction it did the previous time. Why is this? I’ve seen it happen on every microwave I’ve used, do all models do it? ---
**Author:** ![robcaro](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@robcaro](https://boards.straightdope.com/u/robcaro)\ **Post date:** [November 30, 2003, 8:32pm UTC](https://boards.straightdope.com/t/microwave-ovens/216094/2 "2003-11-30T20:32:15Z")
That happens in my current microwave oven too. I don’t know why, but I suppose it is a standard feature for turntables. ---
**Author:** ![ParentalAdvisory](https://avatars.discourse-cdn.com/v4/letter/p/53a042/32.png) [@ParentalAdvisory](https://boards.straightdope.com/u/ParentalAdvisory)\ **Post date:** [November 30, 2003, 9:27pm UTC](https://boards.straightdope.com/t/microwave-ovens/216094/3 "2003-11-30T21:27:51Z")
I don’t think all models do, I’m sure most of the newers ones do though. As for the reverse spinning, there is probably some circuitry in it that reverses the polarity of the spinning motor everytime the door is opened. I guess it’s suppose to cook your meal more efficiently or something. Say you have to cook something for 04:00 min. You can stop it at 02:00 min, stir your food, and when you start it again, it will go the opposite way. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [November 30, 2003, 11:47pm UTC](https://boards.straightdope.com/t/microwave-ovens/216094/4 "2003-11-30T23:47:14Z")
The turntable uses a shaded-pole synchronous motor. The direction it spins when it starts is essentially random. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 1, 2003, 12:07am UTC](https://boards.straightdope.com/t/microwave-ovens/216094/5 "2003-12-01T00:07:26Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*The turntable uses a shaded-pole synchronous motor. The direction it spins when it starts is essentially random. \*\* I had a few minutes wait while cooking supper, so I tested how random it is: Set the timer at two minutes Started the over, and noted the spin direction Opened and closed the door, and restarted 20 times The spin sequence was: LLRLRLLLRLRLLRRLRRRR It looks pretty random. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [December 1, 2003, 12:50am UTC](https://boards.straightdope.com/t/microwave-ovens/216094/6 "2003-12-01T00:50:51Z")
**Desmostylus** is right. DC motors use brushes and a commutator to reverse the flow of current in the rotor as it turns to ensure that opposing fields continue to turn it. Some types of AC motor use the inherent alternation of current in the mains supply to achieve a similar effect, but as a result of this, the direction of rotation is affected by the position in which the rotor is resting and the direction in which the alternating current happens to be flowing when the thing is powered up.