Dielectric?

Question

A certain dielectric with a dielectric constant k= 24 can withstand an electric field of 4*10^7 V/m. Suppose we want to use this dielectric to construct a 0.85uF capacitor that can withstand a potential difference of 1660V.

a. What is the minimum plate separation (in mm)?

b. What must the area of the plates be (in cm^2)?

Answer 1

Let's start with C = k*A/d

C: Capacitance (given as 0.85 uF)
k: Dielectric constant (given as 24)
A: Area of plates
d: Distance between plates (separation)

Now, knowing that the material can withstand 4*10^7 V/m and the requirement for the capacitor is 1660 V, we can calculate the maximum thickness (minimum plate separation) of the material:

d = 1660 V / 4*10^7 V/m

Finally, we plug this value back in to the first equation, rearrange and solve for A. Just make sure your units all work out. I would calculate everything in m and convert to mm or cm^2 only at the end.

-trickshottim