# Homework Help: Circuits problem verification

1. Nov 29, 2006

### Number2Pencil

in the circuit attached, find the voltage across the 2 kilo-ohm resistor.
I got -17.82 Volts<0...but that doesn't match up with the answer guide (-10.667Volts<0).

I used nodal analysis:

Va (left node): 12mA<0 + Va/2Kohm - 2mA<0 + (Va - Vb)/1kohm = 0
Vb : 2mA<0 + (Vb - Va)/1Kohm + (Vb - 6Vx)/3.3Kohm = 0
Dependent source supplemental: Va - Vb = Vx

2. Nov 29, 2006

### Number2Pencil

Here is the circuit again...

#### Attached Files:

• ###### circuits prob.JPG
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3. Nov 30, 2006

### Staff: Mentor

Thread moved to the homework forums. Number2Pencil -- please do not post regular homework problems in the EE forum or other general forums. I think you should know better by now. I'll be back in a minute to try to offer some help on this homework question of yours.

4. Nov 30, 2006

### Staff: Mentor

Double-check the sign convention you are using for Vx and the current through the 1k resistor....

5. Nov 30, 2006

### doodle

Hmm... I can't find any mistake on your part.

6. Nov 30, 2006

### Staff: Mentor

Are you adding the currents into a node or out of a node?

7. Nov 30, 2006

### doodle

He seems to be adding the currents leaving the node.

8. Nov 30, 2006

### Number2Pencil

adding the currents leaving the node

9. Nov 30, 2006

### Staff: Mentor

Okay, your initial equations look correct. Can you show each step in your work that got you to your answer? If there's an error, it must be in there.

10. Nov 30, 2006

### Number2Pencil

sure: This is done in the TI-89

Solve( .012<0 + x/2000 - .002<0 + (x-y)/1000 = 0 , y)

ans ~> y this stores y as a function of x

Solve (.002<0 + (y - x)/1000 + ((y - 6(x - y))/3300) = 0 , x)

this is where I get -17.821 V <0.

I tried it with determinants and i think i got the same thing

11. Dec 1, 2006

### doodle

Yup, my answer's the same too. The given answer is possibly incorrect- that happens sometimes.

12. Dec 1, 2006

### Number2Pencil

Yup, I even had my teacher comfirm today that the book answer was wrong. I hate when this happens because it makes me second guess my way of doing these problems...

Thanks for the double checking everyone

13. Dec 10, 2006

### m_niknam

please send me a circuit diagram of termometer

14. Dec 10, 2006

### Staff: Mentor

Welcome to the Physics and Math Forums. Your post makes no sense -- can you please elaborate?

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