Capacitor directly connected to a DC battery.

Click For Summary

Homework Help Overview

This discussion revolves around the behavior of a capacitor connected directly to a DC battery at the moment the circuit is completed. The focus is on the initial conditions and potential differences between the capacitor plates and the battery terminals.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to determine the potential of the battery terminals relative to the capacitor plates at the moment the circuit is closed, questioning whether the positive and negative terminals can be at specific voltage levels.
  • Participants discuss the implications of the capacitor being initially discharged and the voltage measurements relative to the battery's negative terminal.
  • Questions are raised about the validity of different voltage pairs for the battery terminals and their relationship to the capacitor's behavior.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the voltage relationships in the circuit. Some guidance has been offered regarding the initial conditions and voltage measurements, but no consensus has been reached on the specific voltage values for the battery terminals.

Contextual Notes

Participants are considering the initial state of the capacitor and the battery, with emphasis on the moment the switch is closed. There is a focus on the assumptions regarding voltage levels and the behavior of the circuit components at that instant.

vissh
Messages
82
Reaction score
0
HeyoO everyone (^_^) and Thanks for your time.

Homework Statement


This question is about the "intial" point of time i.e. as soon as the key is closed.
Before the current starts to flow which charges the capacitor till the voltage of capacitor is equal to voltage across the battery.

A capacitor,C is directly connected to a DC battery of (say) 10V.
If the plates of the capacitor are taken to be at 0V, then what would be potential of "negative" and "positive" terminal
of battery relative to the plates?


Homework Equations


Electrons likes to flow from "Low" to "High" potential.

Finally, the plate A will be "Positively" charged and plate B will be negatively charged.
That means Electrons flowed from A -> X -> Positive terminal -> Negative terminal -> Y -> B which created those charges on Plate A and B.

This implies that Initially (the time at which this question is to be answered) Plate A [ 0V ] was at a lower potential than the positive terminal of the battery... And... Plate B [ 0V] was at a higher potential than the negative terminal of the battery.

A battery is of 10V implies that the potenital difference between the +ve and -ve terminal is of 10V.



The Attempt at a Solution


I think that the +ve terminal will be at +5V and -ve terminal will be at -5V.
That is +"Half of the voltage" on positive terminal and -"half of voltage" on negative terminal.

[Q.01] Am i right (o.O) ??


[Q.02] Will other pairs of (+ve Terinal , -ve terminal) work out?? :
Like (+9V , -1V) or (+4V, -6V).


[Q.03] The pair (+13V , +3V) will not be correct right ??
 

Attachments

  • ask.jpg
    ask.jpg
    9.6 KB · Views: 526
Physics news on Phys.org
Ok I see the switch is in red.

So the initial conditions are switch open and the capacitor discharged.

It's necessary to state that the following voltages are measured with respect to the -ve terminal of the battery...

The A terminal of the capacitor (and point X) is the same voltage as the +ve terminal as the battery eg 10V.

The B terminal of the capacitor (and point Y) is the same voltage as the A terminal (eg 10V) because the capacitor is discharged.
 
Last edited:
The way to think of this is that at t=0 when the switch is closed/ON the B terminal of the capacitor will be "pulled down" from 10V to 0V.
 
Consider this circuit.

The discharged condition is represented by SW1 closed and SW2 open.
The charged condition is represented by SW1 open and SW2 closed.
 

Attachments

  • Untitled.png
    Untitled.png
    6.9 KB · Views: 487

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
5
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 12 ·
Replies
12
Views
1K
Replies
9
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 30 ·
2
Replies
30
Views
3K
  • · Replies 18 ·
Replies
18
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K