RC circuit with dc current source

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SUMMARY

The discussion focuses on solving a circuit involving a direct current (DC) source and a capacitor, specifically addressing the calculation of currents in each branch over time. The mesh method is employed to set up equations, utilizing the impedance of the capacitor defined as Zc = 1/(ωC). Participants express confusion regarding the integration of both a capacitor and a current source, as well as the derivation of the voltage across the current source as a function of time. The need for initial conditions, such as the capacitor voltage at t=0, is highlighted as crucial for solving the problem.

PREREQUISITES
  • Understanding of mesh analysis in electrical circuits
  • Familiarity with capacitor impedance (Zc) and its time-dependent behavior
  • Knowledge of differential equations and Laplace transformations
  • Basic concepts of direct current (DC) circuits
NEXT STEPS
  • Study the application of Laplace transformations in circuit analysis
  • Learn how to derive time-dependent expressions for voltages and currents in RC circuits
  • Explore initial condition assumptions in circuit analysis
  • Review steady-state analysis for circuits with capacitors and current sources
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in analyzing RC circuits with direct current sources will benefit from this discussion.

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Homework Statement


Solve for the current in each branch of the following circuit as a function of time & derive and expression for the time dependence of the emf of the constant current source in the circuit below.


Homework Equations



Zc = Xc = 1/(wC) = t/(2pi*C)


The Attempt at a Solution



I attempted to use the mesh method:

Loop 1:
-1000(i1)+50-(Zc)(i1)+(Zc)(i2)=0

Loop 2
-(Zc)(i2)+(Zc)(i1)-3500(i2)+3500(i3)=0

Loop3:
-3500(i3)+3500(i2)-5000(i3)-V=0

This quickly got confusing when I substituted Zc for t/(2pi*120mF).
I have no idea how to solve this problem when it has both a capacitor and a current source.

I also do not understand what the second part of the question is asking.

I would appreciate any help/insight that you could offer. Thanks.
 

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We can't see your picture until it's been approved, but I can tell you that for these kind of questions, usually, you have to either use differential equations or Laplace transformations. I assume you're familiar with one of them?

The second part gets me too. I can understand each word separately, but put them together and it's jibberish to me. :blushing:
 
The 2nd part asks for the voltage across the current source, as a function of time.

As a start, you could get the steady-state currents and voltages (t→∞).

To solve this, I think we need some initial condition that isn't given. For example, perhaps the capacitor voltage is zero at t=0?
 
That's all the information that I'm given. I have a feeling that since the current varies with time that I have to treat it like an ac circuit, and put in a function instead of i. I'm meeting with my prof today, so hopefully he provides some more insight.
 

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