Microwave Science Experiments - Will it blow up? What can we stick in? Microwave Night at MITERS

MITERS is a creative heaven for MIT inventor types and practical physicists. We have build parties every Friday at 7 in N52-115, and anyone is welcome to come check it out and build something.

This build party, we got an old junky microwave from a thrift store, and put any interesting thing into it, before stripping it of its transformers and turning it into a welder.

Our microwave doesn't have a turntable, but it does have an impeller, which is a piece of metal outside the oven chamber that spins and changes the magnetic resonance of the box to keep standing waves from forming.

Picturing that, or at least keeping it in mind, will give you a clearer idea of why the grapes arc inconsistently, why the lightbulbs don't stay on, etc.

Photos and videos, courtesy of Jordi Castell, posted here so you can hold your own Microwave-It night!

You can also see the original photo/images at http://evalu29.uv.es/~jordi/build_party/

Step 1 Grapes

So, when you cut a grape in half (almost, but not quite fully sliced), they're about the same length as a half-wave of 2.4GHz radiation (which are microwaves).

That means that when you put them in a microwave, they resonate and the energy builds up until the juice boils and creates an ionized gas, and then arcs across the two halves.

We tried it with blueberries too, as they're almost the same size. It did work, but not quite as well.

They don't taste very good afterwards.

Here's what plasma physics on grapes looks like:

Comments

[jack.spigack]

once i put a raw egg yolk on a plate to see how it would cook... i watched it for a few minutes but it didnt appear to be cooking so i opened the microwave door to inspect the egg yolk and within a second or two the egg yolk exploded all over the place and made a big mess i wasnt thrilled about cleaning up.... it was very awsome

[Askabby]

O my gosh thats is soooooo awsume and after u were probably like, y did this happen to me? :)

[ilpug]

I am going to do the grape thing tomorrow in the school cafeteria just for entertainment. Does it still work if the grapes are on a revolving tray?

[Treknology]

An impeller, and a turntable actually linked to the on/off cycle of the magnetron would vastly improve wave distribution.

[technodude92]

Does the grape plasma harm the microwave?

[a_traceur]

Not really, just a ton of power drain which could cause an overheat. Plasma, If I'm correct, is atoms being stripped of their electrons. A neon light bulb uses plasma and so it's just light, and not fire.

[panstar1]

(removed by author or community request)

[Xellers]

Actually, in RF circuits, everything tends to become an inductor.

[gomiboy]

I plan on doing this with the kids and a junk microwave. Would the effects look better if I take the lightbulb out of the mircowave? That way the light show would happen in the dark....

[stasterisk]

Sure, you could do that. I found that turning the room lights off was enough, and the microwave light was helpful with for seeing the grape and soap experiments

[bullet-head]

once my sister but a pop tart in the microwave still in the foil and it blew up the whole microwave jumped in the air!!!

[SeaLion]

Should try really really hot peppers, I heard they'll catch fire...

[j626no]

if you want the real reason, its because there are loads of mini air pockets in the soap (thus it floats in water...that was their initial sales pitch that got them on the market -- it would float in the bathtub while the others would sink.) The soap (as i'm sure you know) is still usable after this is done. the only thing i was curious about, is after it expands and you use it, does it last longer than the original bar would? if so, this would be great for people on tight budgets or people that want to protect the environment more (less soap down the drain). just a few thoughts.

[surfreak]

Nah, probably last about the same. This foam is less dense, so more volume, but you'd use more volume per wash.

[Maxx1]

Cool, Just avoid using pets....lol Cucumbers work real good.

[TimAnderson]

Swank!

[hay_jumper]

RAD. Sorry I missed this one Star. When I did the grape/plasma thing I used a much larger variety of fruit and it made a huge ZZORPP! sound which sent my roommie running from the other side of the apartment all alarmed. I don't know what it's called but it's available at most bodegas around here. Next up is bronze and steel, yess?

[ijius]

try putting some rock salt or pickling salt in a bowl. i'll melt the salt + whatever if youleave it long enough.

[GorillazMiko]

I am always amazed at how little grapes can do so much besides tasting yummy.