Help Thevenin equivalent

Discussion in 'Homework Help' started by integralx2, Sep 27, 2008.

1. integralx2 Thread Starter New Member

Sep 27, 2008
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How do i find the current 1 k olhm resistor thats to the left. I see that 4mA are going and the 1 am. THen how do i calculate the open circuit voltage ?

Please help , im stuck :\

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2. Ratch New Member

Mar 20, 2007
1,068
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integralx2,

Left of what? There are three 1k resistors.

Ratch

3. veritas Active Member

Feb 7, 2008
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If you call the current in the lower left loop I1, in the upper left I2, and in the upper right I3, then you can see that I1 is the only current flowing through the left-most 1k resistor.

Voc will end up being V(ac) + V(cd) + V(de), because it's not possible to directly determine the voltage across a current source.

4. integralx2 Thread Starter New Member

Sep 27, 2008
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Yes veritas you are right on that, but how do i calculate the current through the resistor i circled in attachment. I am not underdstand this part of it .

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5. silvrstring Active Member

Mar 27, 2008
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Integralx2,

The current flowing through that resistor will just be the sum of the upper left loop current and the bottom loop current. Each of those loop values are predetermined to their current source. The upper left loop to 4mA and lower loop to 1mA.

6. integralx2 Thread Starter New Member

Sep 27, 2008
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Then the Voc how would that equation be , cause im confused

7. silvrstring Active Member

Mar 27, 2008
159
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integralx2,

Here is an example for solving Vth.

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8. integralx2 Thread Starter New Member

Sep 27, 2008
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picture not working

9. silvrstring Active Member

Mar 27, 2008
159
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Really? It's just a jpg. Can you view it at all?

I can't scan again right now. So I'll send it again via personal message, and I'll try to post again when my annoying roommate gets off the other PC with the scanner.

10. The Electrician AAC Fanatic!

Oct 9, 2007
2,283
326
Silvrstring, the circuit in your solution has different component values the the original problem. Have you applied some kind of transformation that you didn't explain?

11. The Electrician AAC Fanatic!

Oct 9, 2007
2,283
326
Rth is easy to find. Delete (open) all the current sources, and you will see that the resistance from terminal A to terminal B is plainly 3k ohms.

12. silvrstring Active Member

Mar 27, 2008
159
0
I don't want to do the problem for him; I'm trying to show him how to do it. The example I gave is the same problem, but with different values.

Sorry integralx2, can't send right now. Having problems with Vista.