A parallel-plate capacitor is made from two plates 14.0 c m on each side and 4.2
ID: 2126438 • Letter: A
Question
A parallel-plate capacitor is made from two plates 14.0cm on each side and 4.25mm apart. Half of the space between these plates contains only air, but the other half is filled with Plexiglas of dielectric constant 3.10. (See the figure below(Figure 1) .) An 19.5V battery is connected across the plates.
Explanation / Answer
For the capactiance, C = keA/d
C = (8.85 X 10^-12)(.14)(.14)/(2.125 X 10^-3/1 + 2.125 X 10^-3/3.1)
C = 6.17 X 10^-11 F which is 61.7 pF
The charge would be from Q = CV
Q = (6.17 X 10^-11)(19.5)
Q = 1.20 X 10^-9 C (1.20 nC)