Circuit analysis using Laplace

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Thread Starter

Grétar Már

Joined Feb 4, 2018
2
In the following pdf file, I have calculated a circuit using Laplace. I was asked to find v(t) over the capacitor for all t > 0. The switch opens at t=0. Is this right or wrong? (The text in the pdf file is in icelandic)
 

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WBahn

Joined Mar 31, 2012
24,698
Since it's a first order circuit, you should be able to figure out the initial voltage and the time constant by much simpler means to confirm or disprove your Laplace-based solution.

Since you don't bother properly tracking units, I have to guess that the '2' in the exponential has units of inverse seconds, making the time constant 0.5 seconds. Does that make sense?

Your own work says that the capacitor voltage at t = 0- is 18 V. Does that agree with your solution?

What do you know about the voltage across a capacitor as changes are made to a circuit?

Always, always, ALWAYS ask if your answer makes sense.
 

Thread Starter

Grétar Már

Joined Feb 4, 2018
2
Since it's a first order circuit, you should be able to figure out the initial voltage and the time constant by much simpler means to confirm or disprove your Laplace-based solution.

Since you don't bother properly tracking units, I have to guess that the '2' in the exponential has units of inverse seconds, making the time constant 0.5 seconds. Does that make sense?

Your own work says that the capacitor voltage at t = 0- is 18 V. Does that agree with your solution?

What do you know about the voltage across a capacitor as changes are made to a circuit?

Always, always, ALWAYS ask if your answer makes sense.
Thank you for the answer, it helped :)
 
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