Answer to Question #263742 in Physics for viktor

Question

(a)

A certain parallel plate capacitor has plates of area 3.60 m2, separated by 0.0200 mm of nylon, and stores 0.175 C of charge. What is the applied voltage (in V)?

0.175

Incorrect: Your answer is incorrect.

V

(b)

What is unreasonable about this result?

(c)

Which assumptions are responsible or inconsistent?

Answer 1

a) $C=\frac{\epsilon\epsilon_0A}{d}=\frac{3.4\cdot8.85\cdot10^{-12}\cdot3.6}{0.00002}=5.4\cdot10^{-6}\ (C)$

$C=q/U\to U=q/C=0.175/(5.4\cdot10^{-6})=32407\ (V)$

b) This voltage is too high. The dielectric strength for nylon is $E=14\cdot10^6 \ (V/m)$. In our case

$E=32407/0.00002=1620\cdot10^6\ (V/m)$. This is 116 times more strength than the

maximum allowable.

c) It is unreasonable to think that the plates have a charge of $0.175 \ (C)$ .