How Can a Capacitor be Charged to the Voltage of the Battery in an RC Circuit?

Click For Summary

Homework Help Overview

The discussion revolves around an RC circuit where a resistor is connected before a capacitor, powered by a 10V battery. Participants are exploring how the capacitor can be charged to the battery's voltage despite the voltage drop across the resistor, as described by Ohm's Law and Kirchhoff's Law.

Discussion Character

  • Conceptual clarification, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster expresses confusion about how current can flow when the voltage drop across the resistor is equal to the battery voltage. They question the relationship between voltage and current in the circuit and seek clarification on how the capacitor can reach the battery voltage.
  • Some participants discuss Kirchhoff's Law, noting that the sum of voltage drops in a closed loop must equal zero, which leads to questions about the behavior of voltage across the capacitor and resistor over time.
  • Others inquire about the differential equation relating current and charge in the circuit, suggesting that understanding this relationship is key to grasping the circuit's behavior.

Discussion Status

The discussion is active, with participants raising questions and providing insights into the circuit's behavior. Some guidance has been offered regarding the application of Kirchhoff's Law and the differential equation that describes the circuit, but there is no explicit consensus on the understanding of the concepts involved.

Contextual Notes

Participants are navigating assumptions about voltage, current, and the role of the resistor in the circuit. There is mention of the need to consider self-inductance for a complete understanding, indicating that the discussion may involve complexities beyond the basic RC circuit model.

kfreshn
Messages
5
Reaction score
0
Resistor Capacitance Circuits.Say there is a resistor before a capacitor connected in a wired circuit; and there is a battery as the emf source (10V for example).

Chapter2960.gif


How can the capacitor be charged to approx. the voltage of the battery if the voltage drop across the resistor = the voltage of the battery (V=IR and Kirschoff's Law states the voltage drop across the resistor should equal the Voltage of the battery)?

I guess I'm having trouble understanding how a resistor can reduce voltage of the circuit to 0, and yet current is still able to flow after it leaves the resistor --- albeit at a slower rate?.

I thought of Voltage = 0, there would be no more current movement. Need explanation on this.

And how can the Capacitor be charged to the voltage of the battery. If voltage drop across resistor is 10V, how can the capacitor be charged to 10V?

ugh.

Thanks for all the help in advance.

I'll Forever grateful for anyone who can help me asap :)
 
Last edited:
Physics news on Phys.org
kfreshn said:
Resistor Capacitance Circuits.


Say there is a resistor before a capacitor connected in a wired circuit; and there is a battery as the emf source (10V for example).

Chapter2960.gif


How can the capacitor be charged to approx. the voltage of the battery if the voltage drop across the resistor = the voltage of the battery (V=IR and Kirschoff's Law states the voltage drop across the resistor should equal the Voltage of the battery)?

I guess I'm having trouble understanding how a resistor can reduce voltage of the circuit to 0, and yet current is still able to flow after it leaves the resistor --- albeit at a slower rate?.

I thought of Voltage = 0, there would be no more current movement. Need explanation on this.

And how can the Capacitor be charged to the voltage of the battery. If voltage drop across resistor is 10V, how can the capacitor be charged to 10V?

ugh.

Thanks for all the help in advance.

I'll Forever grateful for anyone who can help me asap :)

Welcome to the PF.

(I moved your thread to here in the Homework Help section of the forums, where schoolwork questions like this should be posted.)

Are you familiar with the differential equation that relates v(t) and i(t) for a capacitor? That's really the key to understanding how this circuit behaves. Can you show us that equation?
 
IR(t) + q(t)/C = V(t)?

edit: thanks for the welcome
 
kfreshn said:
harged to approx. the voltage of the battery if the voltage drop across the resistor = the voltage of the battery (V=IR and Kirschoff's Law states the voltage drop across the resistor should equal the Voltage of the battery)?

No, Kirchoff's law says the sum of the voltages around a closed loop should be zero, so the resistor voltage drop PLUS the capacitor voltage drop must add up to the battery voltage. At the end of the charging process, the current goes to zero, which means there is no voltage drop across the resistor, and all of the battery voltage has developed across the capacitor.

Also: what berkeman said.
 
So will the resistor in the RC circuit affect the electric field between the capacitor? V=ED?

Ty for your help.
 
kfreshn said:
IR(t) + q(t)/C = V(t)?

edit: thanks for the welcome

To describe the charging of an RC circuit, you'll need to solve this ODE. First, you need to get it in terms of one variable. How can you write i in terms of q?
[tex]Ri(t) + \frac{1}{C}q(t) = V(t)[/tex]

Note that the solution to this equation is wrong. To accurately describe the circuit, you'll need to take self-inductance into account, which will give you an RLC circuit, which you should get to soon.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
3
Views
2K
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
1K
Replies
14
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
9
Views
1K