Capacitor Charge Density Calculation

In summary, the problem involves calculating the surface charge density on two metal disks separated by a piece of Pyrex glass. The relevant equations are Coulomb's law, capacitance, and charge density. Taking the dielectric constant of Pyrex into account, the solution can be found by multiplying the dielectric constant by the permittivity of free space and the potential difference, and then dividing by the thickness of the glass. The difference between the surface charge density on the glass and the disks can be explained by the electric field strength in the air gap between the glass and the conductor.
  • #1
PhysKid45
12
1

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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  • #2
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?
 
  • #3
Hey, so apparently the answer was in microfarads but I was entering it in farads, but thanks for the help!
 

What is capacitor charge density?

Capacitor charge density is a measure of the amount of electric charge that can be stored in a capacitor per unit volume or area. It is typically measured in coulombs per square meter or coulombs per cubic meter.

How is capacitor charge density calculated?

The capacitor charge density can be calculated by dividing the total charge stored in the capacitor by its physical size or volume. It is also dependent on the dielectric material between the capacitor plates and the distance between them.

What is the relationship between capacitor charge density and voltage?

The capacitor charge density and voltage have an inverse relationship. As the voltage across a capacitor increases, the charge density decreases. This means that a higher voltage can store a smaller amount of charge, and vice versa.

What factors affect the capacitor charge density?

The capacitor charge density is affected by the size and geometry of the capacitor, the dielectric material used, and the voltage applied. Additionally, the temperature and humidity can also impact the charge density.

Why is capacitor charge density important?

Capacitor charge density is an important factor in determining the performance of a capacitor. It affects the capacitance, energy storage capacity, and overall efficiency of the capacitor. It is also crucial in many electronic applications, such as in power supplies, filters, and memory devices.

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