Capacitor Charge Density Calculation

AI Thread Summary
The discussion revolves around calculating the surface charge density on two metal disks and the glass separating them, given a potential difference of 1100 V. The user initially attempted to use the capacitance formula and the dielectric constant of Pyrex but faced confusion regarding the results and the application of the dielectric constant. Clarifications were sought on the differences in surface charge density between the disks and the glass, as well as the impact of an air gap on electric field strength. Ultimately, the user discovered a mistake in unit conversion, realizing that the answer was in microfarads instead of farads. The conversation highlights the importance of understanding dielectric properties and unit consistency in capacitor calculations.
PhysKid45
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Homework Statement


Two 10-cm-diameter metal disks separated by a 0.64-mm-thick piece of Pyrex glass are charged to a potential difference of 1100 V .
What is the surface charge density on the disks?
What is the surface charge density on the glass?

Homework Equations


C=(e_0A)/d
C=Q/V
charge density=Q/A

The Attempt at a Solution



Q/V=(e_0A)/d)
Q=((e_0A)/d)*V
charge density= ((e_0A)/d)*V)/A
charge density=(((8.85*10^-12)(pi*.05^2)*1100/.00064)/(pi*.05^2)

I have also tried multiplying the dielectric constant for pyrex (google gave me 4.7) by e_0 and nothing has worked.

I am not sure what the difference between the surface charge density on the glass vs. the disks would be, or how to find it.
 
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What do you mean by "nothing has worked"? What were the results you got?
Where is the formula taking the dielectric constant into account?
PhysKid45 said:
I am not sure what the difference between the surface charge density on the glass vs. the disks would be, or how to find it.
Imagine adding a very small air gap between glass and conductor. What would be the field strength there? How is the difference between that and the field strength in the glass related to the surface charge density of the glass?
 
Hey, so apparently the answer was in microfarads but I was entering it in farads, but thanks for the help!
 
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