1. A parallel-plate capacitor is constructed using a dielectric material whose d
ID: 1267493 • Letter: 1
Question
1. A parallel-plate capacitor is constructed using a dielectric material whose dielectric constant is 3.60 and whose dielectric strength is 1.60 108 V/m. The desired capacitance is 0.100 µF, and the capacitor must withstand a maximum potential difference of 4.00 kV. Find the minimum area of the capacitor plates.
2. (a) How much charge can be placed on a capacitor with air between the plates before it breaks down if the area of each plate is 9.00 cm2?
(b) Find the maximum charge if paper is used between the plates instead of air.
Explanation / Answer
q/v = c
q = c*v = 0.1*10^-6 4 * 10^3 = 0.4mC
E = Gq / kd^2
1.6 * 10^8 = 9*10^9* * 0.4*10^-3 / 3.6*r^2
r = 0.08m
now C = A*epsilon*k / r
0.1*10^-6 = A*8.854*10^-12 * 3.6 / 0.08
A = 250.95m^2
2) A) Dielectric constant of air = 1
C = q/v = k*A*epsilon / d
q/ 4*10^3 = 1 * 9/10000 * 8.854*10^-12 / 0.08
q = 0.39nC
B) Dielectric constant of paper = 3
C = q/V = k*A*epsilon/d
q/ 4*10^3 = 3 * 9/10000 * 8.854*10^-12 / 0.08
q = 1.20 nC
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