# thevenin again

Discussion in 'Homework Help' started by stupid, Nov 29, 2009.

1. ### stupid Thread Starter Active Member

Oct 18, 2009
81
0
hi,
attached are my working. Pls verify if my answer were correct.

first convert norton part to thevenin.
thus the current-ctrl voltage source is 70i & 20Ω in series with the circuit.

to compute V$_{ab}$,
-10 + 10i + 20i - 70i=0
i= -0.25A

i(20)-(70i)= -5+17.5= 12.5V =V$_{ab}$

next to compute I$_{sc}$
short the ab terminal,
I$_{sc}$= i - 3.5i
v=0,
(-10+v)/10 = -i
i= 1

thus, I$_{sc}$= 1 - 3.5 = -2.5A

hence R$_{th}$= 12.5/-2.5 = -5Ω

i m wondering if i got them right.

• ###### thevenin2.JPG
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Last edited: Nov 29, 2009
2. ### hgmjr Moderator

Jan 28, 2005
9,030
214
It looks as though you forgot to attach your file?

hgmjr

3. ### stupid Thread Starter Active Member

Oct 18, 2009
81
0
i did..pls check again.
thanks

4. ### nirvanaguy New Member

Oct 3, 2009
15
0
To my knowledge you can't have negative resistance.. so maybe your current shoudlnt be negative because I'm pretty sure you got your voltage correctly

5. ### Pinky Ringz New Member

Oct 4, 2009
6
0
remove the load, parallel the resistors until you get a simple series cct, reinsert the load and then calculate....no?

6. ### stupid Thread Starter Active Member

Oct 18, 2009
81
0
is the shorted cct current-ctrl current source a supermesh element?
i m lost at this.

regards,