An experimental apparatus is designed to accelerate an oil droplet of mass from rest…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
An experimental apparatus is designed to accelerate an oil droplet of mass 2.0×10−15kg from rest to a speed of 1.0m/s as it travels horizontally across a 5.0cm gap between two large, parallel, square plates of side length 10cm. The droplet carries a net positive charge of +4.0×10−19C. Air (treated as vacuum, κ=1) fills the gap, and gravitational effects on the droplet are negligible over the short transit time.
Ignore edge effects so that the electric field remains uniform between the plates.
(a) Determine the minimum magnitude of the uniform electric field required to achieve the stated final speed over the 5.0cm distance.
(b) Calculate the potential difference that must exist between the plates to create the electric field found in part (a).
(c) Find the magnitude of the charge that must reside on each plate to establish this field.
(d) Briefly discuss one reason why the assumption of a perfectly uniform field might break down if the plate separation were made much smaller while keeping the same plate dimensions.