Transient RC Circuit (got answer in s but not in t-domain)

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SUMMARY

The discussion focuses on solving a transient RC circuit problem using both Laplace transforms and time-domain analysis. The initial voltage across the capacitor is 50V, and the final voltage is 100V, with a capacitance of 50 microfarads and a resistance of 10 ohms. The participant successfully derived the current through the capacitor as Ic = 5e^(-2000t) using Laplace transforms but struggled with time-domain analysis due to polarity issues. The resolution was achieved by correctly assuming the polarity of the capacitor's initial voltage.

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jaus tail
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Homework Statement


upload_2018-1-24_11-45-7.png


Homework Equations


Vc = ( Initial Voltage - Final Voltage ) e(-RC/t) + Final Voltage

3. The Attempt at a Solution
I got the answer through Laplace but am not getting through time domain analysis.
Given q across C is 2.5mC
C = 50micro F
q = CV
So V = 50V
Initial voltage = 50V
Final voltage = 100V since C will be open circuit on steady state.
Req = 10 ohm
Ceq = 50 micro F
RC = .0005
1/RC = 2000
So applying the underlined formula I get Vc = ( 50 - 100) e(-2000t) + 100
Ic = C dV/dt = 50 micro times (-50 * -2000) e(-2000t)
Ic = 5e(-2000t)

Book answer is A.
 

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The polarity of the capacitor initial voltage is not indicated so you can't solve the problem.
 
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Oh yeah. I tried with polarity of lower plate positive and got answer in time domain. Thanks.
 

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