# Maximum Voltage without causing Dielectric Breakdown? (1 Viewer)

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#### mli273

1. What plate area is required if an air-filled, parallel-plate capacitor with a plate separation of 2.3 mm is to have a capacitance of 24 pF?

Which I found correctly to be 6.2 x 10^-3 m^2 by using the formula C= k(8.85x10^-12)A/d

What is the maximum voltage that can be applied to this capacitor without causing dielectric breakdown?

2. I know V=Q/C, and that I have C, but I'm not sure what to substitute for Q, or if I need another formula completely. Help?

#### Dickfore

You should know the value for the critical electric field Ec in air (the electric field that would cause electric breakdown) and calculate the voltage from the formula:

$$E = V/d$$

#### mli273

3x10^6= V/.0023, so V = 6900 Volts. Thank you, I always have trouble on the simple ones.

#### Dickfore

You have too many significant figures in your end result, by the way. Because you stated the value of the critical field with one significant figure only, it means you should state your maximum voltage with that many significant figures. This should lead to a value of 7 kV.

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