# How to find the Dielectric Strength

1. Nov 28, 2007

### jra_1574

Hello, everyone!

I have a question, and i don't know how to solve it...
They ask me for the dielectric strength!
How do i find it?

2. Nov 28, 2007

### rock.freak667

3. Nov 28, 2007

### jra_1574

The full question is like this:

The square plates of a 9000pF capacitor measure 90mm by 90mm and are separated by a dielectric which is 0.29mm thick. The voltage rating of the capacitor is 300V. THe dielectric strength, in KV/m is closest to:
A. 1300
B. 930
C. 1200
D. 1100
E. 1000

To be honest i have no idea how to approach this problem.

4. Nov 28, 2007

### rock.freak667

for such a capacitor,the capicitance is given by

$$C=\frac{\epsilon_0 A}{d}$$ where d=thickness and A=area

5. Nov 29, 2007

### jra_1574

ok i did the calculation

Eo = 8.85 x10^-12
A= 8.1x10^-3
d = 2.9x10^-4

so the final answer is C = 2.4719x10^-10

Now what should i do?

6. Oct 12, 2009

### rasharma

Can u tell me where did u find the problem coz that was the same question in my exam? So that I can predict future exam qts.

7. Oct 13, 2009

### jra_1574

It was actually in my exam a few years ago.. i solved the problem in class tho... i don't remember the answer, but the equation given here was very useful... :)