Analyzing Parallel RC Circuits with Time Constant Variation

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SUMMARY

This discussion focuses on analyzing parallel RC circuits, specifically addressing the time constant when the switch is closed. Users seek to determine the capacitor's potential at t=2s during the charging phase. The solution involves applying Kirchhoff's laws to derive a differential equation for the capacitor's charge and finding the Thevenin equivalent sources for both open and closed switch scenarios. This method simplifies the analysis into two distinct RC circuits.

PREREQUISITES
  • Understanding of Kirchhoff's laws
  • Familiarity with RC circuit analysis
  • Knowledge of Thevenin's theorem
  • Basic differential equations
NEXT STEPS
  • Study the derivation of the charging equation for capacitors in RC circuits
  • Learn how to apply Thevenin's theorem in circuit analysis
  • Explore differential equations related to capacitor charging
  • Investigate time constant variations in parallel RC circuits
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in analyzing or designing RC circuits will benefit from this discussion.

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the attached file is the question

I know the time constant after opening the switch

but how can i know the time constant when the switch is on?

This is NOT the classic initial and AFTER A LONG LONG LONG Time question

How can i know the potential of C in t=2s ?

What is the equation for charging ?

Plz help, i googled for a long time but still can't get the ans
 
Last edited by a moderator:
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What is the equation for charging ?
With Kirchhoff's laws, you can get a differential equation for the charge of the capacitor. The time constant can be seen in this equation.
 
One approach would be to find the Thevenin equivalent sources that the capacitor "sees" when the switch is open and when the switch is closed. That'll give you two simple RC circuits to work with...
 

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