# The Naked Scientists Forum

### Author Topic: Why do Microwave Oven Plates Spin ?  (Read 27094 times)

#### neilep

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##### Why do Microwave Oven Plates Spin ?
« on: 19/10/2004 23:44:51 »
Hello wonderful People Of Scientific lovliness,

My boy Ben asked me why the plate in the microwave spins and
I was just wondering, is it vital for the plate in my microwave to spin ?...I assume it has to do with the microwaves penetrating equally eh ? but could a microwave oven expert explain to me the principles behind the reason why the plate must spin ?.....I told my son that I wasn't too sure but that I know a place where answers come freely and with a smile

Just 850 watts at 3 minutes of answering will do...many thanks.

Neil

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#### gsmollin

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #1 on: 20/10/2004 04:19:47 »
Like you thought, the plate spins so the food is heated evenly by the microwaves. The wavelength of the radio frequency energy in the microwave is 12.24 cm. The RF energy is bouncing back and forth inside the oven, which is called a cavity. Inside the cavity, the waves appear (if you could see them) to stand still, and are called standing waves. Each standing wave has anti-nodes spaced 1/2 wavelength apart, and at those points, the food is cooked. The bad news is that there are also nodes spaced 1/2 wavelength (6.12 cm) apart where the food does not cook. The spinning plate allows all parts of the food to receive the RF energy. Some ovens have fans spinning in the top of the oven where the RF enters, to break up the standing waves. This method is less effective than the spinning plate, but allows the entire cavity to be used for holding food.

#### Raedon

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #2 on: 20/10/2004 04:29:13 »
until around 83, no microwaves in the States had plates that spun.  In fact I got my parent's old nuker when I moved out for college sooo looong ago..

I loved it!  My roommates and I nicknamed it "The Iradicator" while I was at RIT.  It popped the best popcorn.. no burning :)

I wish I had kept it but it was huge and the lights dimmed when I turned it on.

It is good to be alive! It's impossible I'm here but here I am.. and I rock!

#### Ylide

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #3 on: 20/10/2004 08:30:45 »
I had one of those archaeic scary microwaves in my basement at the last place we lived.  We got rid of it when we moved.  I miss it sometimes...you could nuke a small child in it if you were so inclined.

Raedon, when did you go to RIT?  I was there from 92-94.

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#### Raedon

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #4 on: 20/10/2004 09:57:55 »
'96-'99.

artist.  Film/Video/animation student.. 4th above the photo peeps on the 3rd floor.  Think they call the program SOFA now.

I froze my balls off in that place being a Texan but I loved every minute of my time there.

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#### neilep

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #5 on: 20/10/2004 11:23:58 »
I pose a question, I get an answer.....thanks Gsmollin.

'Men are the same as women...just inside out !'

#### Ylide

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #6 on: 21/10/2004 16:27:36 »
I was film/video for exactly 1 quarter, then dropped out.  That was like my 3rd change of major before I decided that a 25k a year college wasn't the place to "find myself."

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#### gsmollin

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #7 on: 22/10/2004 01:50:48 »
Neil, since your boy has taken an interest in science and technology, you should encourage him. There is a clasic home experiment that shows the standing waves in the microwave oven, and you can measure the speed of light too. Just be sure to use a microwave with a turntable, and remove the turntable. This experiment does not work well with a microwave oven that does not use the turntable. Here's the procedure:

http://www.ahs.k12.wi.us/staff/science/mechenich/speed_of_light_lab.htm

#### neilep

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##### Re: Why do Microwave Oven Plates Spin ?
« Reply #8 on: 22/10/2004 09:04:57 »
Thanks Gsmollin.....that's great...When I get home this evening I'll have marshmallows at the ready....assuming I haven't eaten them all...but Thanks, sounds really good...looking forward to trying it.

'Men are the same as women...just inside out !'

#### The Naked Scientists Forum

##### Re: Why do Microwave Oven Plates Spin ?
« Reply #8 on: 22/10/2004 09:04:57 »