184_notes:charge_and_matter

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184_notes:charge_and_matter [2021/01/24 23:49] – bartonmo184_notes:charge_and_matter [2021/01/25 00:05] – bartonmo
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 If we start with a neutral atom by itself, we know that there will be a positive nucleus with a negative, circular electron cloud around it. The electron cloud is circular (spherical in 3D) because it is equally likely that the electrons are anywhere around the nucleus (shown in Figure 2a/3a).  If we start with a neutral atom by itself, we know that there will be a positive nucleus with a negative, circular electron cloud around it. The electron cloud is circular (spherical in 3D) because it is equally likely that the electrons are anywhere around the nucleus (shown in Figure 2a/3a). 
  
-**What would change about our atom if we put a charge next to a neutral atom?** +//What would change about our atom if we put a charge next to a neutral atom?//
  
 The electrons cannot leave their nucleus (unless [[https://en.wikipedia.org/wiki/Ionization|the interaction is very strong]]), but they are attracted to the positive charge. With a positive charge nearby, it is now more likely that the electrons will be on the left side of nucleus compared to the right (shown in Figure 2b), shifting the electron cloud toward the positive charge. Often, we will simplify this drawing to be just an oval that indicates which side of the atom is more positive and which side is more negative (shown in Figure 2c).   The electrons cannot leave their nucleus (unless [[https://en.wikipedia.org/wiki/Ionization|the interaction is very strong]]), but they are attracted to the positive charge. With a positive charge nearby, it is now more likely that the electrons will be on the left side of nucleus compared to the right (shown in Figure 2b), shifting the electron cloud toward the positive charge. Often, we will simplify this drawing to be just an oval that indicates which side of the atom is more positive and which side is more negative (shown in Figure 2c).  
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 === Insulators === === Insulators ===
-An insulator is an object or material where the electrons are tightly bound to the nucleus. This means that the electrons in an insulator can only move very small amounts and must stay close to their nuclei. //**Charges cannot move freely through an insulator.**// Common insulators include: plastic, glass, rubber, paper, wood, etc. +An insulator is an object or material where the electrons are tightly bound to the nucleus. This means that the electrons in an insulator can only move very small amounts and must stay close to their nuclei. **Charges cannot move freely through an insulator.** Common insulators include: plastic, glass, rubber, paper, wood, etc. 
  
 [{{  184_notes:insulatorpos.png?150|Charge distribution in an insulator from a positive charge}}] [{{  184_notes:insulatorpos.png?150|Charge distribution in an insulator from a positive charge}}]
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 When you put a positive charge next to a conductor (shown in the figure to the left), the electrons in the electron sea are attracted to the surface of the metal closest to the positive charge. This leaves the opposite surface with a positive charge because those atoms now look like they are missing an electron. Since the positive charges are much further away from the positive charge than the negative charges, the attraction from the conductor is much stronger than the repulsion. This means that the positive charge is strongly attracted to the metal even though the metal is overall neutral.  When you put a positive charge next to a conductor (shown in the figure to the left), the electrons in the electron sea are attracted to the surface of the metal closest to the positive charge. This leaves the opposite surface with a positive charge because those atoms now look like they are missing an electron. Since the positive charges are much further away from the positive charge than the negative charges, the attraction from the conductor is much stronger than the repulsion. This means that the positive charge is strongly attracted to the metal even though the metal is overall neutral. 
  
-**Again, the electrons are what moves in both cases.**+//Again, the electrons are what moves in both cases.//
  
 You might have experienced this effect when you were working with the tape challenge in the first class. Your body is mostly composed of salt water, which is a very good conductor. No matter what kind of charge was on your tape, you may have observed that it was always attracted to your hand, sometimes more than it was to the other piece of tape. This microscopic model of conductors would explain why the tape was always attracted to your hand. You might have experienced this effect when you were working with the tape challenge in the first class. Your body is mostly composed of salt water, which is a very good conductor. No matter what kind of charge was on your tape, you may have observed that it was always attracted to your hand, sometimes more than it was to the other piece of tape. This microscopic model of conductors would explain why the tape was always attracted to your hand.
  • 184_notes/charge_and_matter.txt
  • Last modified: 2021/01/25 00:06
  • by bartonmo