ProveISaidIt t1_j2dpc7e wrote
Reply to comment by epelle9 in ELI5: Why plates get too hot to touch in the mircrowave but the food can still be cold? by jerrycotton
Microwave ovens work by causing the water molecules in the food to vibrate. That's how it heats food. You can look it up.
By your explanation a dry plate with no food on it would heat in a microwave.
From what I've always heard that would damage the microwave as there has to be water to absorb the microwave energy.
epelle9 t1_j2eipdo wrote
Yes, it causes the water molecules in the food to vibrate, but if the plate has a similar frequency to the water molecules, then the plate can heat up too.
And yes, if you have a plate that generally heats up more than the food, you can put it in the microwave and it will heat up.
Why are you arguing instead of listening? I have a major in physics engineering, I know what I'm talking about. Your explanation literally violated one of the basic thermodynamic laws.
Seems like Dunning Krueger effect in action.
ProveISaidIt t1_j2emh70 wrote
Trying to understand a concept isn't the and as arguing. Also, you may have lead with the major in physics.
As stated, I only draw from my experience. That is articles I've read and videos from SciShow and the like.
If I hold a metal rod with a metal pair of pliers and heat the far end of the rod, the piers will heat up from hear transfer.
That's about as far as my understanding of thermodynamics goes.
I have never heard of plates having resonant frequencies as microwaves. That, however, does not mean it's not true, only that I have more to learn.
ProveISaidIt t1_j2ew3y6 wrote
I took a look at the first law of thermodynamics. Way too complicated for a quick read. I wasn't a science major.
It talks about energy in a closed system. Isnt the microwave inputting additional energy while it is running?
If you don't mind educating me a bit by continuing the dialog. I find science fascinating. Sadly, I didn't get the science gene. My dad was a chemist, one brother a biochemist, the other brother was mechanically minded. Even my daughter and niece are in the sciences.
I read articles, watch videos and grasp at concepts.
epelle9 t1_j2ftj0f wrote
Well, it's actually the second law that states this, not the first one. It says that heat flows from the object with higher temperature to the object with lower temperature.
How a microwave basically works is that it sends out microwaves at a certain frequency that they interact with water.
It basically interacts with most polar molecules causing them to spin and heat up. Since water is a polar molecule that can interact with microwave frequencies, it interacts with them, absorbing the wave and as a result producing heat. Transforming the electromagnetic energy (since microwaves are electromagnetic waves) into thermal energy.
But water isn't the only polar molecule that can interact with microwave frequencies of electromagnetic waves, other molecules can have that same interaction too.
So when you put a plate (or any object) into the microwave that also has molecules that interact with microwave frequencies, that plate (or those objects) also heat up just like water would.
If you want to know what causes the molecules to spin, it's that their polarity (which is linked to its dipole moment) wants to align with electromagnetic fields, and the microwaves (as well as any electromagnetic wave), is just a disruption to the magnetic field, so the polar molecules wants to align with the constantly changing electromagnetic field.
Water (H2O) is a polar molecule because of it's structure, since the molecule is formed at an angle, with the O molecules going the opposite side as the H molecule, since O is more electronegative, it attracts the electrons to one side, causing that side to have more negative charge and the other side a positive one.
Think of it as every water molecule being a compass, with one side negatively charged and the other positively. It wants to align with the world's electromagnetic field and point north. Now if you bombard the world with other electromagnetic waves, the field will be constantly changing and causing the compass to spin fast, which would cause friction that ends up being heat.
But it would heat up all compasses, not just the ones created from X material. And there are many molecules that are polar, not just water.
ProveISaidIt t1_j2fuy7h wrote
Thank you. I had heard microwave was discovered because it melted a chocolate bar in some guys pocket. I knew that you can use them to ionize the gas in florescent tubes and freak out the Boatswains Mates or so I'd heard. I was in the US Navy Reserve for a spell.
I didn't know things like dishware would heat up on its own. We got our first microwave 40 years ago as mentioned. The warning was always never to run the oven without something moist to absorb the energy. So I've never put just a plate in.
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