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| 184_notes:q_in_wires [2021/02/18 21:17] – bartonmo | 184_notes:q_in_wires [2021/02/23 20:23] – [Hypothesis 2 - There are stationary charges on the surface of the wires] bartonmo | ||
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| 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. | ||
| - | However this is problematic for a few of reasons: | + | **However this is problematic for a few of reasons:** |
| - If the electric field is smaller in some parts of the wire than others, this would mean that the electrons move faster in parts of the wire (where the electric field is bigger - close to the battery) and slower in other parts of the wire (where the electric field is smaller - in the middle of the wire). We can measure the electron current at each part of the wire in such a circuit and show that this is not in fact true. //The electron current close to the battery is exactly the same as the electron current in the middle of the wire// | - If the electric field is smaller in some parts of the wire than others, this would mean that the electrons move faster in parts of the wire (where the electric field is bigger - close to the battery) and slower in other parts of the wire (where the electric field is smaller - in the middle of the wire). We can measure the electron current at each part of the wire in such a circuit and show that this is not in fact true. //The electron current close to the battery is exactly the same as the electron current in the middle of the wire// | ||
| - The electric field from the battery plates would always point either left or right (away the positive plate and towards the negative plate); thus, this electric field could never push the electrons down or up the vertical parts of the wires, let alone explain how the electrons are able to bend around the corner of the wire. | - The electric field from the battery plates would always point either left or right (away the positive plate and towards the negative plate); thus, this electric field could never push the electrons down or up the vertical parts of the wires, let alone explain how the electrons are able to bend around the corner of the wire. | ||
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| Because the wire is made of metal, electrons are free to move and any excess charge will move to the surface of the wire. Thus, when connected to the battery, **there are charges on the surface of the wire**, which contribute to the net electric field in the wire (in addition to the field from the battery). | Because the wire is made of metal, electrons are free to move and any excess charge will move to the surface of the wire. Thus, when connected to the battery, **there are charges on the surface of the wire**, which contribute to the net electric field in the wire (in addition to the field from the battery). | ||
| - | For example, near the negative end of the mechanical battery, there are negative charges on the surface of the wire. Near the positive end of the mechanical battery, there are positive charges on the surface of the wire. Moving farther from the negative end of the battery will result in less and less negative surface charges, with the same effect as you move farther from the positive end. In the middle, there must be a place where the surface charge is zero (where the surface charge switches from positive to negative). **This creates a __continuous | + | For example, near the negative end of the mechanical battery, there are negative charges on the surface of the wire. Near the positive end of the mechanical battery, there are positive charges on the surface of the wire. Moving farther from the negative end of the battery will result in less and less negative surface charges, with the same effect as you move farther from the positive end. In the middle, there must be a place where the surface charge is zero (where the surface charge switches from positive to negative). **This creates a // |