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184_notes:pc_force [2019/01/04 00:48] – dmcpadden | 184_notes:pc_force [2021/01/26 21:15] – bartonmo |
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Sections 3.7, 13.2 - 13.3 , and 13.6 of Matter and Interactions (4th edition) | Sections 3.7, 13.2 - 13.3 , and 13.6 of Matter and Interactions (4th edition) |
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[[184_notes:pc_energy|Next Page: Electric Potential Energy]] | /*[[184_notes:pc_energy|Next Page: Electric Potential Energy]] |
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[[184_notes:charging_discharging|Previous Page: Charging and Discharging]] | [[184_notes:charging_discharging|Previous Page: Charging and Discharging]]*/ |
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===== Electric Force ===== | ===== Electric Force ===== |
* [[https://en.wikipedia.org/wiki/Newton's_laws_of_motion#Newton.27s_3rd_Law|Newton's third law]] still applies - The electric force from one charge on a second charge is equal and opposite to the electric force from the second charge on the first. | * [[https://en.wikipedia.org/wiki/Newton's_laws_of_motion#Newton.27s_3rd_Law|Newton's third law]] still applies - The electric force from one charge on a second charge is equal and opposite to the electric force from the second charge on the first. |
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=== The electric force is a conservative force === | ==== The electric force is a conservative force ==== |
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In addition to the general results above, the electric force is also a [[https://en.wikipedia.org/wiki/Conservative_force|**conservative force**]]. A conservative force is a force: | In addition to the general results above, the electric force is also a [[https://en.wikipedia.org/wiki/Conservative_force|**conservative force**]]. A conservative force is a force: |
Two examples of conservative forces from mechanics include: the gravitational force and the spring force. It doesn't matter how you go from $y=3m$ to $y=5m$, the change in gravitational energy ([[183_notes:grav_and_spring_pe|which is defined as PE=mgh]]) is the same. This is in contrast to **non-conservative force**, which result in changes to the system energy that depend on the path the system takes. You cannot define a potential energy for non-conservative forces. Examples of non-conservative forces that you may know from mechanics are: the friction force and air drag. In these cases we cannot define what the "energy of friction" would be, in part because it depends on what path you take (e.g., the thermal energy change due to friction on a squiggly path between two points would be much higher than on a straight path between those same points). | Two examples of conservative forces from mechanics include: the gravitational force and the spring force. It doesn't matter how you go from $y=3m$ to $y=5m$, the change in gravitational energy ([[183_notes:grav_and_spring_pe|which is defined as PE=mgh]]) is the same. This is in contrast to **non-conservative force**, which result in changes to the system energy that depend on the path the system takes. You cannot define a potential energy for non-conservative forces. Examples of non-conservative forces that you may know from mechanics are: the friction force and air drag. In these cases we cannot define what the "energy of friction" would be, in part because it depends on what path you take (e.g., the thermal energy change due to friction on a squiggly path between two points would be much higher than on a straight path between those same points). |
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=== Two Point Charges === | ==== Two Point Charges ==== |
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[{{ 184_notes:electricforce.png?200|Negative and positive point charges, with the separation vector from the negative charge to the positive charge. }}] | [{{ 184_notes:electricforce.png?200|Negative and positive point charges, with the separation vector from the negative charge to the positive charge. }}] |