ugh my girlfriend ran her microwave without a load! EDIT: STILL WORKS FINE

[Buttzilla]

Originally posted by: Elemental007
Ugh.

So I'm sitting here workin on a lab, and I hear her running the microwave. Since she is making split pea soup I don't think anything of it. I go out there a few minutes later and ask her what she is microwaving:

"Oh, nothing, I just needed a timer for two minutes."

I give her a nice, blank stare.

What are the odds the microwave will ever work again? I know that running it without a load is akin to running a short -circuit. Will her microwave still work or is it effectively toasted? The microwave is late 80s, early 90s, judging from the design - it came embedded into her stovetop on the kitchen.

UPDATE:

From: http://rabi.phys.virginia.edu/HTW//microwave_ovens.html

This goes to show that the general consensus is not always the right one.

"Why are you required to have an item in the microwave oven while it is operating?

When a microwave oven is cooking food, electrons move rhythmically back and forth inside the magnetron tube and create the microwaves. These microwaves flow through a metal pipe and into the cooking chamber, where they are absorbed by the water in the food and thus heat the food (the twisting back and forth of the water molecules, described elsewhere on this page, not only heats the food--it also absorbs the microwaves). If there is no food in the cooking chamber, the microwaves build up in the cooking chamber until they are so intense that large numbers of them flow backward through the pipe to the magnetron. These microwaves reenter the magnetron and disrupt the motion of electrons inside it. The magnetron begins to misbehave and can be damaged as a result. To avoid such damage, you want to be sure that there is something in the cooking chamber to absorb the microwaves before they return to the magnetron and cause trouble. In short, don't run the microwave empty for any long periods of time."

And I specifically KNEW this was a bad thing because at the end of the 80s, when I was like 3, I broke a microwave oven by doing this for five minutes. I was four years old and still remember how mad my parents were, because they weren't $60 pieces of equipment you could find at Best Buy at the time.

EDIT2 : Why do I call it a load?

We've discussed this problem in my second circuits class. A microwave oven is a linear circuit and can be modeled, somewhat simplistically, as a thevenin equivalent circuit which consists of a voltage source, and a resistor in series.

you can simplistically model a microwave oven by this. Any food you put into it can be modeled as a resistive load. If you run it without nothing in it, it is like creating a short between the terminals of the thevenin equivalent circuit.

Hence the name load.

thats an awsome link. i like the questions and answers he gives.

 

[Ausm]

Originally posted by: Anubis
theres nothing wrong with that

Ditto

Ausm

 

[Slammy1]

Originally posted by: Buttzilla
thats an awsome link. i like the questions and answers he gives.

"The cooking chamber of a microwave oven has mesh-covered holes to permit air to enter and exit. The holes in the metal mesh are small enough that the microwaves themselves cannot pass through and are instead reflected back into the cooking chamber. However, those holes are large enough that air (or light in the case of the viewing window) can pass through easily. Sending air through the cooking chamber keeps the cooking chamber from turning into a conventional hot oven and it carries food smells out into the kitchen."

He's saying the holes are so small they do not permit the light waves from entering? Maybe he's just trying to dumb things down for the masses, but that's pretty weird.

 

[Eli]

LOL.........

I don't know... I mean, what if the object your heating is small, like say a cup of coffee or a small dish of food? What if the microwave is putting out more energy than the object can absorb?

Why do microwaves last for 25+ years if they're so easily damaged?

 

[T2T III]

Originally posted by: piku
Who calls what they put into a microwave a load?

I was thinking the same thing.

 

[godmare]

Originally posted by: Slammy1

Originally posted by: Buttzilla
thats an awsome link. i like the questions and answers he gives.

"The cooking chamber of a microwave oven has mesh-covered holes to permit air to enter and exit. The holes in the metal mesh are small enough that the microwaves themselves cannot pass through and are instead reflected back into the cooking chamber. However, those holes are large enough that air (or light in the case of the viewing window) can pass through easily. Sending air through the cooking chamber keeps the cooking chamber from turning into a conventional hot oven and it carries food smells out into the kitchen."

He's saying the holes are so small they do not permit the light waves from entering? Maybe he's just trying to dumb things down for the masses, but that's pretty weird.

try reading that again....

 

[Eli]

Originally posted by: Slammy1

Originally posted by: Buttzilla
thats an awsome link. i like the questions and answers he gives.

"The cooking chamber of a microwave oven has mesh-covered holes to permit air to enter and exit. The holes in the metal mesh are small enough that the microwaves themselves cannot pass through and are instead reflected back into the cooking chamber. However, those holes are large enough that air (or light in the case of the viewing window) can pass through easily. Sending air through the cooking chamber keeps the cooking chamber from turning into a conventional hot oven and it carries food smells out into the kitchen."

He's saying the holes are so small they do not permit the light waves from entering? Maybe he's just trying to dumb things down for the masses, but that's pretty weird.

No. He's talking about the door. You can see the mesh.. of course the holes aren't literal holes into the cooking chamber, but clear plastic.

I wouldn't mind getting a microwave emissions tester.. I'd like to see how many mW my old huge 1200W 80s microwave leaks.

 

[Eli]

Originally posted by: Slammy1

Originally posted by: Buttzilla
thats an awsome link. i like the questions and answers he gives.

"The cooking chamber of a microwave oven has mesh-covered holes to permit air to enter and exit. The holes in the metal mesh are small enough that the microwaves themselves cannot pass through and are instead reflected back into the cooking chamber. However, those holes are large enough that air (or light in the case of the viewing window) can pass through easily. Sending air through the cooking chamber keeps the cooking chamber from turning into a conventional hot oven and it carries food smells out into the kitchen."

He's saying the holes are so small they do not permit the light waves from entering? Maybe he's just trying to dumb things down for the masses, but that's pretty weird.

No. He's talking about the door. You can see the mesh.. of course the holes aren't literal holes into the cooking chamber, but clear plastic.

I wouldn't mind getting a microwave emissions tester.. I'd like to see how many mW my old huge 1200W 80s microwave leaks.

 

[Eli]

Originally posted by: Slammy1

Originally posted by: Buttzilla
thats an awsome link. i like the questions and answers he gives.

"The cooking chamber of a microwave oven has mesh-covered holes to permit air to enter and exit. The holes in the metal mesh are small enough that the microwaves themselves cannot pass through and are instead reflected back into the cooking chamber. However, those holes are large enough that air (or light in the case of the viewing window) can pass through easily. Sending air through the cooking chamber keeps the cooking chamber from turning into a conventional hot oven and it carries food smells out into the kitchen."

He's saying the holes are so small they do not permit the light waves from entering? Maybe he's just trying to dumb things down for the masses, but that's pretty weird.

 

[Eli]

Originally posted by: Slammy1

Originally posted by: Buttzilla
thats an awsome link. i like the questions and answers he gives.

"The cooking chamber of a microwave oven has mesh-covered holes to permit air to enter and exit. The holes in the metal mesh are small enough that the microwaves themselves cannot pass through and are instead reflected back into the cooking chamber. However, those holes are large enough that air (or light in the case of the viewing window) can pass through easily. Sending air through the cooking chamber keeps the cooking chamber from turning into a conventional hot oven and it carries food smells out into the kitchen."

He's saying the holes are so small they do not permit the light waves from entering? Maybe he's just trying to dumb things down for the masses, but that's pretty weird.

 

[Slammy1]

He says they're small enough that the microwaves cannot get through, and microwaves are merely lightwaves of a specific energy. Smell soes not come through the door of the microwave, but instead out a vent in the back (a fan bows them out). And, I do not believe microwaves "bounce around in a chamber" as he seems to imply, but instead are directed through the "load" from a source 1X. I'm not a microwave repairman, so I may be off on some of the finer points.

 

[cressida]

that's enough EE for you today.

 

[beer]

Originally posted by: KenGr
I think most newer microwaves have protection circuits to prevent overheating, so it's probably low risk of damage.

That said, I've used microwaves as timers lots of times. All you have to do is set the power level to 0, the power unit never starts and the timer works. No danger.

What kind of microwave doesn't have a timer function?

The microwave has neither a '0 power' function, nor a timer. Like I said, it is really, really old. But it still works. I used it to heat instant coffee this morning.

 

[beer]

Originally posted by: piku

Originally posted by: Elemental007
EDIT2 : Why do I call it a load?

We've discussed this problem in my second circuits class. A microwave oven is a linear circuit and can be modeled, somewhat simplistically, as a thevenin equivalent circuit which consists of a voltage source, and a resistor in series.

you can simplistically model a microwave oven by this. Any food you put into it can be modeled as a resistive load. If you run it without nothing in it, it is like creating a short between the terminals of the thevenin equivalent circuit.

Hence the name load.

Ah, gotcha.

However, I will continue to eat my popcorn and you can continue to eat your loads.

That's fvcking hilarious. I just spit coffee. Congrats.

 

[slackerinabox]

You don't deserve a girlfriend.

 

[Nitemare]

Is she related to the woman that tried to dry her cat in the microwave?

 

[Scarpozzi]

Most microwaves have the heavy glass platform. This prevents it from ever being "empty". If I remember correctly, the majority of the energy of a microwave is directed at the bottom and would be absorbed by the glass plate if there was nothing else present. Magnetrons in microwaves are pretty strong too. It would take a lot of sustained abuse to really hurt one.

 

[abracadabra1]

what was she thinking?!

make sure she gets some EE training ASAP.

 

[Colt45]

how is a microwave "solid state" when the magnetron is a tube..

i guess the diodes feeding it are SS, but the magnetron itself isnt.. kind of a stupid gimmick.

just like "solid state CRT TV" its not entirely SS, because the CRT is a tube. just the driving circuitry is no longer tube.


i love it when you see something like a toaster, and it says "solid state". theres no fvckin' active components in the first place!

 

[Ornery]

Originally posted by: ausm

Originally posted by: Anubis
theres nothing wrong with that

Ditto

Ausm

What do you know that the manufacturer doesn't?