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Question:
I am a biology student at the University of Washington and I have three questions which have been puzzling me for some time. 1. If I press my hand down upon a table, why does not it fall through? Does it have to do with molecules colliding or electrostatic interactions? What if I could shrink an object so that it could fit in the "spaces" between atoms? Would it then fall through? Textbooks illustrate atoms as solid spheres for ease I have been told. There are suppose to be electron "clouds" around the nucleus. If so how come these spaces are not seen? 2. How does electricity work? So what if there are a bunch of electrons moving and generating a current? How does t this translate into something that powers my toaster? 3. How do laundry dryer sheets prevent static "cling"? I would really appreciate any answers. Thanks.



Replies:
I can try to answer first two questions.

1. When you try to press your hand upon the table, the electron clouds of atoms in your hands interact with electrons of atoms in the table. There is a law of nature which prevents two electrons from being in the same state, it is known as the Pauli exclusion principle. For this reason, the electron clouds of different atoms repel each other and it takes a lot of energy to overcome this force. Atoms are incessantly vibrating and colliding with one another, so the "space" between them is not "empty" in the usual sense.

2. When electrons move through simple gadgets like a toaster or an electric bulb, the work is being done by the heat generated from collisions of electrons with nuclei in the filament. For more complicated equipment, various other laws of atomic and material science are used to produce the end result. For example there are things like a diode which will let current pass in only one direction. A combination of such elements produces the result you see.

jasjeet s bagla


As Jasjeet says, in spite of atoms being mostly "empty space", it takes an awful lot of energy to squish atoms together closer than they would normally like to be, because to do that means distorting the shape of those electron 'clouds', and electrons really HATE that... in fact, the energy unit usually used to describe distortion of electron orbitals is the electron-Volt (the energy gained by an electron in an electric potential with a one volt drop). Translated into ordinary temperature terms, one electron Volt is equivalent to about 11,000 degrees C. You would have to be pressing your hand REAL hard to generate temperatures that high (and you would probably do structural damage to the table first...) I also do not know how those dryer sheets work... I assume they act in some way that removes any charge accumulation on materials they come in contact with, so perhaps they can conduct electricity reasonably well? But that is just a guess!

Arthur Smith



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