Calculating Charge and Time in a Discharging RC Circuit

Click For Summary

Homework Help Overview

The discussion revolves around an RC circuit involving a resistor, capacitor, and a switch, with specific values for voltage, resistance, and capacitance. Participants are exploring the charge on the capacitor and the time it takes for the current to reach a specified value after closing the switch.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to relate the charge on the capacitor to the current using the equation ΔVC - IR = 0 and considers using Q = Q0 e^(-t/RC) to find the time. Some participants question the calculation of Q0 and seek clarification on its derivation.

Discussion Status

The discussion is active, with participants confirming the original poster's approach while also probing for further details regarding the initial charge on the capacitor. There is an ongoing exploration of the relationships between the circuit components.

Contextual Notes

Participants are discussing the implications of the initial conditions of the circuit and the assumptions made regarding the charge and current relationships. There is a request for additional information, such as a circuit diagram, which may be relevant for a complete understanding.

Moolisa
Messages
20
Reaction score
5

Homework Statement


RC circuit, with a resistor, capacitor and a switch with
ΔVC =80V R=1.5MΩ C=22μF
The switch is initially open. The switch is closed at t=0
(a) What is the charge in the capacitor when the current is 33μA
(b) How times does it take for the current to reach 33μA
2. The attempt at a solution
(a) So I think the capacitor is discharching.
Since ΔVC -IR=0, and ΔVC=Q/C is the charge when I=33μA
Q=IRC?
(b) If part (a) is correct, can I use Q=Q0 e-t/RC and find the time from there?
 
Physics news on Phys.org
It looks correct to me. For part b, how do you compute ## Q_o ##? I don't think you showed that.
 
  • Like
Likes   Reactions: Moolisa
Charles Link said:
It looks correct to me. For part b, how do you compute ## Q_o ##? I don't think you showed that.
Is it C(80V)?
 
  • Like
Likes   Reactions: Charles Link
I'd like to see the circuit.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 10 ·
Replies
10
Views
7K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
7K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
20
Views
4K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 13 ·
Replies
13
Views
3K