Maximum Voltage without causing Dielectric Breakdown?

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Homework Help Overview

The discussion revolves around calculating the maximum voltage for an air-filled parallel-plate capacitor, given its capacitance and plate separation. The subject area includes concepts from electrostatics and capacitor theory.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to determine the maximum voltage without causing dielectric breakdown, seeking clarification on the necessary parameters, particularly the charge (Q) needed for calculations. Some participants suggest using the critical electric field value to derive the voltage, while others discuss the implications of significant figures in the final result.

Discussion Status

Participants are exploring different methods to calculate the maximum voltage, with some providing guidance on using the electric field and voltage relationship. There is an acknowledgment of the importance of significant figures in the final answer, indicating a productive direction in the discussion.

Contextual Notes

There is a mention of the critical electric field value for air, which is essential for determining the maximum voltage, but the original poster's uncertainty about the charge (Q) remains a point of discussion.

mli273
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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?
 
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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:

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