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I Electromagnetism and injury -- physical contact at the molecular level...

  1. Jul 1, 2016 #1
    So here is my question, and maybe I am not asking it right, but here we go: If electromagnetism prevents me from actually touching anything at a quantum level, how is it that I can get cut by a knife, or get a road rash falling off my bike? If the negative field of electrons that surround everything repel each other, how does a knife penetrate and cut my skin? This may be a ridiculous question, but it has always puzzled me.

  2. jcsd
  3. Jul 1, 2016 #2
    The simple answer is that of length scales. The dermis and subcutaneous layer are composed of cells which are composed of molecules which are ultimately composed of elemental atoms. Getting cut by a knife or falling off of your bike and getting road rash divides the skin and destroys some of the cells along the split. The cut does not extend down to the atomic or sub atomic scale (although there may be weak ionization of individual atoms).

    You might also note that the net charge of your skin cannot be very skewed either negatively or positively otherwise your body would come apart due to the strong repulsion. Does this answer your question?
  4. Jul 1, 2016 #3
    I think it helps for sure. It will also help me narrow my focus to research the topic.

    Something else that I was thinking about, was the difference in charge between two compounds, elements, and atoms. Steel has more Protons and Neutrons than a skin cell does. A skin cell which is comprised mainly of Oxygen, Hydrogen, Carbon, and Phosphorus (in a very basic sense) would have less electrons than the steel knife. The electrons from the knife would repel the electrons in the skin and cause the skin cells to split their bond from each other. Thus, cutting you (this may be what you said). I don't know if this is realistic or not, but it was something I was thinking about while I was cleaning my house and trying to entertain my 1 year old daughter. I originally asked her, and if she did know, I didn't understand her. Ha!

    I appreciate the response!
  5. Jul 10, 2016 #4
    Sorry for not responding sooner...

    The knife cutting is a physical process resulting in little change in the atomic or molecular constituents of either the blade or the skin. The number of protons.neutrons/electrons is (nearly) irrelevant because the electrons shield the positively charged nucleus from coming in contact with another + nucleus. The electrons will merely deform their orbital structures as another atom is pushed closely. If you were to surround the entire skin/knife volume with an imaginary balloon you would measure little to know effective charge because they are both nearly neutral.

    I say nearly irrelevant because a slight imbalance of charge is responsible for the bonding of both the Fe atoms in the steel and the O,H,C and P of the skin through ionic and covalent bonding.

    What you are describing is an electrochemical process which might only happen if the knife was charged up significantly relative to the skin. This is a common practice in dermatology as it automatically cauterizes the exposed would (electric scalpel :nb)).
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