Area of a Parallel Plate capacitor. Pi*r^2?

AI Thread Summary
The discussion revolves around the calculation of the area for a parallel plate capacitor, specifically addressing the use of the formula pi*r^2 for a circular electrode. The initial confusion arises from the assumption that the area should be based on the length of one electrode multiplied by the distance between electrodes. It is clarified that the relevant area is indeed that of one electrode, where the charge resides. This understanding aligns with the formula for electric field calculation, E=sigma/epsilon0. The conversation concludes with a consensus on the correct interpretation of the area in this context.
Specimen
Messages
15
Reaction score
0
Hi,

I was just going through a question in my Physics textbook today. In calculating the electric field (E=sigma/epsilon0) ... sigma = charge density = q/Area ... they have used the area as pi*r^2, I can't understand why this was done? shouldn't the area of the parallel plate capacitor be length of one electrode * distance between electrodes?

Hope I'm making sense!
 
Physics news on Phys.org
No, the area that we use here is the area of one of the electrodes (circular in this case, apparently). The charge resides on the electrodes, not in the space between them.
 
Hmm, makes sense. Thanks mate!
 

Thread 'Maxwell stress tensor'

This is from Griffiths' Electrodynamics, 3rd edition, page 352. I am trying to calculate the divergence of the Maxwell stress tensor. The tensor is given as ##T_{ij} =\epsilon_0 (E_iE_j-\frac 1 2 \delta_{ij} E^2)+\frac 1 {\mu_0}(B_iB_j-\frac 1 2 \delta_{ij} B^2)##. To make things easier, I just want to focus on the part with the electrical field, i.e. I want to find the divergence of ##E_{ij}=E_iE_j-\frac 1 2 \delta_{ij}E^2##. In matrix form, this tensor should look like this...
View full post »
Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'

Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'

Please can anyone either:- (1) point me to a derivation of the perpendicular force (Fy) between two very long parallel wires carrying steady currents utilising the formula of Gauss for the force F along the line r between 2 charges? Or alternatively (2) point out where I have gone wrong in my method? I am having problems with calculating the direction and magnitude of the force as expected from modern (Biot-Savart-Maxwell-Lorentz) formula. Here is my method and results so far:- This...
View full post »

Similar threads

I Parallel plate capacitor, charge imbalance VS charge redistribution
Replies
1
Views
918
I Is capacitor energy the electrostatic energy of the whole system?
Replies
9
Views
2K
Prove to me how capacitors in parallel can have the same V across plates
Replies
7
Views
2K
B Electric Field Created by 2 Infinite Plates
Replies
1
Views
1K
I Speed of Electricity in Plate Capacitor & Cable
Replies
18
Views
2K
Electric field outside a parallel plate capacitor
Replies
7
Views
19K
I Capacitor surface charge movement current, relativistic effects
Replies
2
Views
1K
Why Do Capacitor Plates Have Equal and Opposite Charges?
3
Replies
103
Views
7K
Potential Gradient for individual charges and parallel plates?
Replies
33
Views
5K
Disconnected vs Connected parallel plate capacitor
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top