# Answer check to challenging problem

Discussion in 'Homework Help' started by ihaveaquestion, Sep 20, 2009.

1. ### ihaveaquestion Thread Starter Active Member

May 1, 2009
314
0
This is a challenging problem to me, so I'd like to make sure my thinking is correct for my way of solving:

http://img24.imageshack.us/img24/88/imguu.jpg

http://img23.imageshack.us/img23/8479/img0001ty.jpg

Given the original circuit drawn at the top (in the first link), I am asked to find the voltage vo by using Thevenin's theorem. So the strategy is to find Vth, find Rth, then use voltage division to find vo, i.e. vo = Vth(2) / Rth + 2.

I do normal nodal analysis to find Vth = V2 in the first link.

On the second link I find Rth by replacing the 2ohm resistor by a 1V voltage source, shorting the original voltage source, and do nodal analysis again. In this circuit with the excitation 1v voltage, I know v2 = 1v... so I find out what V1 is... the reason for all of this is because I want to determine what the current through my excitation voltage source is so I can determine Rth by Vs / i1 (labeled in my work). Once I find out what V1 is I do KCL at v2... I'm wondering if the directions of the currents at v2 matters... I said the current coming in from the left into V2 was v1-v2/j2... I calculate i1 (current through excitation Vs) and calculate Rth...

I finally do my voltage division with my Thevenin equiv..

what do you guys think?

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Replace the capacitors and inductor with their equivalent impedance. Remove the 2R resistor and find Vth. Then replace the voltage source by a short circuit and the current source by an open circuit and find the impedance (Rth) looking into the terminals across the 2R resistor (without 2R connected).

3. ### ihaveaquestion Thread Starter Active Member

May 1, 2009
314
0
This is shown in my work.

The current source is dependent, can't open circuit it. This is why I applied the 1v source in my work.

4. ### ihaveaquestion Thread Starter Active Member

May 1, 2009
314
0
As an FYI - you don't need to check all my numbers, just want confirmation that my procedure and way of thinking is correct.