- #1
thuc
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Member warned to use the homework template for posts in the homework sections of PF.
Problems with First order RC circuit
- Context: Engineering
- Thread starter thuc
- Start date
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- Tags
- Circuit First order Rc Rc circuit
Click For Summary
Discussion Overview
The discussion revolves around the analysis of a first-order RC circuit, specifically focusing on the behavior of the circuit when a switch is closed and then opened. Participants are addressing the theoretical and practical aspects of the circuit's response over time, particularly in relation to voltage across the capacitor.
Discussion Character
- Technical explanation
- Homework-related
- Conceptual clarification
Main Points Raised
- One participant expresses confusion about the initial conditions when the switch is in steady state, noting that the current through the capacitor would be zero and questioning the implications for their calculations.
- Another participant describes the circuit configuration, including a 12V power source with internal resistance and a parallel RC circuit, and requests clarification on the method for solving part (a) of the problem.
- There is a request for clarification on the physical behavior of the capacitor when the switch is opened after being closed for a long time, specifically regarding the initial voltage and charge dynamics.
- One participant references the response of a series RC circuit to a step input and inquires about familiarity with Thevenin's theorem, suggesting these concepts may be relevant to the discussion.
Areas of Agreement / Disagreement
The discussion reflects uncertainty and confusion regarding the initial conditions and the behavior of the circuit in different states. Participants have not reached a consensus on the approach to solving the problem, and multiple viewpoints on the analysis are present.
Contextual Notes
Participants have not fully defined the assumptions regarding the initial voltage on the capacitor or the implications of the switch's state on the circuit's behavior. There are unresolved questions about the mathematical steps needed to analyze the circuit's response.
Who May Find This Useful
This discussion may be useful for students or individuals studying electrical engineering or circuit analysis, particularly those interested in first-order circuits and transient response behavior.
- #2
Simon Bridge
Science Advisor
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The image shows a 12V power source with 2##\Omega## internal resistance connected, in parallel, with a parallel RC circuit (3F and 4##\Omega##) via a switch.
The voltage across the capacitor is labelled ##v_0##.
Part (a) says the switch, open for a long time, is closed at t=0, find ##v_0(t)##.
Part (b) says the switch has been closed for a long time, and is opened at t=0, find ##v_0(t)##.
These two parts normally have a similar method of solution, so please show your method for part (a) so we can see how you are thinking.
For part (b) ... what is physically happening? What is the initial voltage on the capactor, what happens to the charge on the capacitor for t>0?
The voltage across the capacitor is labelled ##v_0##.
Part (a) says the switch, open for a long time, is closed at t=0, find ##v_0(t)##.
Part (b) says the switch has been closed for a long time, and is opened at t=0, find ##v_0(t)##.
These two parts normally have a similar method of solution, so please show your method for part (a) so we can see how you are thinking.
For part (b) ... what is physically happening? What is the initial voltage on the capactor, what happens to the charge on the capacitor for t>0?
- #3
- #4
cnh1995
Homework Helper
Gold Member
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Are you familiar with the response of a series RC circuit excited with a step input?thuc said:
Are you familiar with the Thevenin's theorem?
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