184_notes:q_in_wires

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184_notes:q_in_wires [2020/08/23 19:20] dmcpadden184_notes:q_in_wires [2021/02/18 20:14] bartonmo
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 We will start with the simplest circuit possible: a battery connected by a conducting wire (shown to the right). If we //__assume the battery is a mechanical battery__//, then we should have a constant amount of charge on each of the plates (one side of the battery being the positive plate and one side being the negative plate). Much like the example before, we would expect the electrons to flow from the negative plate through the wire to the positive end of the plate (with the only difference being that the chemical "conveyer belt" would now move the electrons from the positive plate back to the negative plate to start the cycle over again).  We will start with the simplest circuit possible: a battery connected by a conducting wire (shown to the right). If we //__assume the battery is a mechanical battery__//, then we should have a constant amount of charge on each of the plates (one side of the battery being the positive plate and one side being the negative plate). Much like the example before, we would expect the electrons to flow from the negative plate through the wire to the positive end of the plate (with the only difference being that the chemical "conveyer belt" would now move the electrons from the positive plate back to the negative plate to start the cycle over again). 
  
-If the electrons are moving, there has to be some sort of force that is making those charges move. From what we talked about before, we know we can write this force on the electron in terms of the electron charge and the electric field it is in:+If the electrons are moving, there has to be some sort of force that is making those charges move. [[184_notes:pc_force|From what we talked about before]], we know we can write this force on the electron in terms of the electron charge and the electric field it is in:
 $$\vec{F}_{e^-}=q_{e^-}\vec{E}$$  $$\vec{F}_{e^-}=q_{e^-}\vec{E}$$ 
  
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 [{{  184_notes:microcircuit.png?350|Hypothesis 1 - Simple circuit: shows the electric field at 3 points in the wire from ONLY the mechanical battery}}] [{{  184_notes:microcircuit.png?350|Hypothesis 1 - Simple circuit: shows the electric field at 3 points in the wire from ONLY the mechanical battery}}]
  
-=== Hypothesis 1 - Electric field comes from the battery alone ===+==== Hypothesis 1 - Electric field comes from the battery alone ====
  
 If this were true, the electric field at Point 1 in the wire would point to left given that it is near the positive plate. Likewise, the electric field at Point 2 would also point to the left, given that it is near the negative plate. At Point 3, we would expect the electric field to be point to the right because it is between the positive and negative plates, though it would be smaller because it is further away from the plates.  If this were true, the electric field at Point 1 in the wire would point to left given that it is near the positive plate. Likewise, the electric field at Point 2 would also point to the left, given that it is near the negative plate. At Point 3, we would expect the electric field to be point to the right because it is between the positive and negative plates, though it would be smaller because it is further away from the plates. 
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 This tells us that while the battery certainly contributes to the electric field in the wire, **there must be something else that is adding to the electric field in the wire**.  This tells us that while the battery certainly contributes to the electric field in the wire, **there must be something else that is adding to the electric field in the wire**. 
  
-=== Hypothesis 2 - There are stationary charges on the surface of the wires ===+==== Hypothesis 2 - There are stationary charges on the surface of the wires ====
  
 [{{  184_notes:circuitefield.png?300|Hypothesis 2 - Simple circuit: shows the electric field in the wire from the charges on the surface of the wire}}] [{{  184_notes:circuitefield.png?300|Hypothesis 2 - Simple circuit: shows the electric field in the wire from the charges on the surface of the wire}}]
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-=== Electric field in the wire follows the surface charge gradient ===+==== Electric field in the wire follows the surface charge gradient ====
  
 The electric field around the circuit then follows the charge gradient, pointing from more positive areas of the wire to less positive areas (or from less negative areas to more negative areas). Ultimately, this means that the **electric field follows the wire pointing from the positive end of the battery to the negative**. Remember that because electrons are negative charges, [[184_notes:pc_force|they will move in the direction opposite of the electric field]]. In a circuit then, the electrons that are driven by the mechanical battery follow the wire opposite to the electric field that is set up by the surface charges.  The electric field around the circuit then follows the charge gradient, pointing from more positive areas of the wire to less positive areas (or from less negative areas to more negative areas). Ultimately, this means that the **electric field follows the wire pointing from the positive end of the battery to the negative**. Remember that because electrons are negative charges, [[184_notes:pc_force|they will move in the direction opposite of the electric field]]. In a circuit then, the electrons that are driven by the mechanical battery follow the wire opposite to the electric field that is set up by the surface charges. 
  • 184_notes/q_in_wires.txt
  • Last modified: 2021/06/08 00:38
  • by schram45