# Dependent Source

Discussion in 'Homework Help' started by salmanshaheen_88, Mar 21, 2009.

1. ### salmanshaheen_88 Thread Starter Active Member

Mar 5, 2009
88
1
how to find Vs. I applied kcl and equations comes out to be
-Vo/2000 + Vs/6k + Vs/(1k+2k) + 2mA= 0

Now how to solve this equation???

Jan 28, 2005
9,030
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hgmjr

3. ### steveb Senior Member

Jul 3, 2008
2,433
469
This problem is poorly defined. There is a voltage dependent current source which depends on the voltage Vo. However, there is no definition of where that voltage is referenced to. I would assume the intention is to draw a ground symbol on the bottom node and reference Vo to ground.

Also, you made a mistake in applying KCL. - Check it again. Further, KCL alone will not give you the answer. You need to bring in other equations.

EDIT: Another comment about the schematic is that you left out the connection dots for the 6K resistor. I'ts ok to either use, or not use connection dots, but if you you them, you should be consistent.

Last edited: Mar 21, 2009
4. ### salmanshaheen_88 Thread Starter Active Member

Mar 5, 2009
88
1
I posted the diagram and as it is in my book? and tell me whats wrong with the equation???

5. ### salmanshaheen_88 Thread Starter Active Member

Mar 5, 2009
88
1
at the end of my book Vo is given to be 8v while Vs is given 12v.can u guys prove it now

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
Answers Vs=12 V and Vo= 8V are correct.

7. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
Write two unknown currents on the circuit diagram.

Let's call the current in the 6K, I1 and the current in the series 1K/2K, I2.

The following should be true:-

Vo = 2000*I2
I2 = Vs/3000
Vs = I1*6000
I1 + I2 = V0/2000 + 2E-3

That's enough info to solve for Vs & Vo ....

8. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
Small typo maybe ....in the 4th equation

I1 + I2 = Vo/2000 + 2e-3

Hopefully you got it anyway!

9. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
There's a slightly more elegant method of solving :-

Let Req = effective resistance = 6K // 3k = 2K

Note that the voltage divider gives Vo = (2/3) x Vs

So the controlled source

Vo/2000 = Vs/3000

and hence

Vs = (Vs/3000 + 2e-3) x Req

etc ....

10. ### nathancole New Member

Apr 3, 2009
1
0
I was a little stuck on this problem too. Found in my book Basic Engineering Circuit Analysis 7e by J. David Irwin.

Earlier in the book they mention that the output voltage for something like would be....

Vo=2k/(2k+1k)Vs

So, then you can plug that in and solve. Last guy hit it right on the head.

You definently have enough information to solve for Vo