An electron travels through a region containing two consecutive sets of parallel plates

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

An electron travels through a region containing two consecutive sets of parallel plates. It begins at plate 1 and ends at plate 3, passing through plate 2 on the way. Measured electric potentials are: • Plate 1: −40 V-40\,\text{V} • Plate 2: +120 V+120\,\text{V} • Plate 3: +60 V+60\,\text{V} Assume the electron is released from rest at plate 1 and that the only force acting on it is electrostatic. Use the electron mass me=9.11×10−31 kgm_e = 9.11\times10^{-31}\,\text{kg} and charge magnitude e=1.60×10−19 Ce = 1.60\times10^{-19}\,\text{C}. (a) Determine the net electric potential difference experienced by the electron as it travels from plate 1 to plate 3. (b) Calculate the change in electric potential energy of the electron–field system over the entire trip. (c) Find the electron’s speed immediately after it has passed plate 3.

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