The plates on a vacuum capacitor have a radius of 2.5 mm and are separated by a distance of 0.75 mm. what is the capacitance of this capacitor? 2.3 × 10–13 f 9.3 × 10–11 f 3.0 × 10–11 f 2.3 × 10–10 f

The capacitance of a parallel-plate capacitor in free space is given by:

where
is the permittivity of free space
A is the area of the plates
d is their separation

For the capacitor in our problem, , so their area is

while the separation between the plates is


Therefore the capacitance is


And correct answer is A).

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