##C##=##\frac{aε0}{d}##gneill said:
No. That has two capacitance terms. You need a voltage and a capacitance: Q = CV.gracy said:
Still too hasty. You've written the same thing againgracy said:
But hint says plate B would have different charge.gneill said:
Yes. I presume "plate B" is the middle plate of the physical setup? You didn't label your diagram.gracy said:
gneill said:
gneill said:
No, "earth" is a vast pool of available charges, both positive and negative and overall neutral. It can supply whatever charge is required to respond to electrostatic forces. Or, if you like, it can source or sink any amount of electrons, if you want to go with an atomic model for the plates and conductors.gracy said:
I did not understand that.gneill said:
V is taken to be a voltage supply. Voltage is a potential difference. When a terminal is just labeled "V" then it is assumed that that potential difference is between the terminal and the ground reference.gracy said:
I don't quite get the relationship between being symmetrical and connected to the same potential and having same charge distribution.gneill said:
gracy said:
That is for one capacitor(1-2 or 3-4). The capacitors are in parallel. So you can find the total charge now.gracy said:
If you rotate the drawing on the page, do you expect the charges on the plates to change? Is there any distinction (electrically) between the two outer plates?gracy said:
You'll have to explain how you ended up with different distributions on the two outer plates.
gracy said:
Its 'grounded' i.e it is at 0 potential. It doesn't have to be an actual earthing. It can be battery's -ve terminal.gracy said:
Now you've shown all the plates neutral. There should be net charge on each plate.gracy said:
As in here V is potential difference between A and Bgneill said:
Just because question says find the" charge".If this question appeared as MCQ and option was to be zero then?cnh1995 said:
I did not understand.cnh1995 said:
No. Charges will be "pushed onto" the outer plates by the voltage supply, and "pushed off" the middle plate via the ground connection. The plates will not remain neutral since charge can enter or leave via their external connections. In other words, there's no reason to balance the charges on the faces of any given plate so that they will sum to zero.gracy said:
You yourself correctly interpreted the circuit as two capacitors in parallel connected across some voltage V. So the plates MUST have a net charge.gracy said:
Right. Here's an alternative depiction of your circuit:gracy said:
The symbol used is normally called 'ground' i.e. a reference point in the circuit. Normally, it is the negative terminal of the battery (exceptions do exist), however, you can choose any point in the circuit as reference. All the voltages are measured w.r.t. that point. Earthing is done from protection point of view. Anyways, this is not the point of the discussion, so I won't say much.gracy said:
That's the 'perfect' description of the circuit.gneill said:
You can see it here.gracy said:
If there is a voltage connected to plates then it is impossible that plates would be neutral?gneill said:
In general plates can be neutral, but they don't have to be if there are external connections over which charges can enter or leave them. Isolated plates are always neutral unless some charge has been deposited on them by some agency.gracy said:
here voltage supplier and earth?gneill said:
Right.gracy said:
While that is all true, I'm not sure that introducing that distinction at this juncture is going to help Gracy with the immediate details that she needs to clear up. Perhaps it can be addressed as a new topic later?jbriggs444 said:
That would depend upon whether or not the connects lead to something that will cause charge to flow (impose potential differences). Even so it is possible to arrange things so that the net excess charge will be zero! Here's an example:gracy said:
But plate A and C have plus charges,right?gneill said:
Seeing this diagram,can I say there won't be net charge on any plate because there isn't any 'closed electrical path "through" the dielectric'?gneill said:
No, one will be plus, the other minus. Look at the polarities of the two batteries. One establishes plate a at +V potential with respect to ground, the other establishes plate c at -V potential with respect to ground.gracy said:
Yeah..right..gneill said:
No, the electric fields between the plates established by the potential differences suffices to influence charge movement in the plates and wiring. Remove the central plate from the scenario and you have a typical capacitor with a potential difference of 2V across it.cnh1995 said:
So can I conclude plates A and C form a capacitor with space between them as dielectric and middle metal plate is just "polarized" because of the the electric field of the two plates.gneill said:
Plate b would have negative charges on it because of plate a and would have positive charges on it because of plate c,right?gneill said:
Effectively yes, but note that the gaps between the middle plate and the outer ones are much smaller than the gap between the two outer plates. So the "new" capacitors thus formed will have higher capacitance than the two outer plates alone would have (recall the formula for capacitance of a parallel plate capacitor).cnh1995 said:
Right.gneill said:
Correct.gracy said:
