Electric Forces

 Parallel Plate Capacitor

 Whiteboard

 In the illustration below we have a pair of oppositely charged capacitor plates positioned as shown.  For the following questions we also have a particle of mass m.  The particle has a +q charge that is small enough that it does not effect the charge distribution of our plates.  Gravitational and other forces are negligible and should not be considered.  DV denotes the potential difference between the capacitor plates.  The distance between the plates is defined as Ds.  E gives the strength of the electrical field between the plates. Q1:  In the diagram above there are three locations denoted by the letters A, B, and C. Draw separate force diagrams for our particle when placed at each location.  Show the net force acting on the particle.  If the net force equals zero, state this as your answer.  Explain your answer. Q2: Suppose our particle is moved from point D to point E, with constant velocity like a bead on a frictionless wire.  Explain what work must be done by (or removed from) our system.  Explain your answer. Q3: Suppose our particle is moved from point F to point G.  How much work must be done by (or removed from) our system.  Explain your answer.

 References

 Arons, A. (1997), Teaching Introductory Physics, Wiley: NY, p. 76.

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