Why Is My Calculated Voltage Across the 2k Resistor Incorrect?

[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

 

[Number2Pencil]

Here is the circuit again...

 

[berkeman]

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.

 

[berkeman]

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

 

[doodle]

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

 

[berkeman]

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

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

 

[doodle]

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

He seems to be adding the currents leaving the node.

 

[Number2Pencil]

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

adding the currents leaving the node

 

[berkeman]

adding the currents leaving the node

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.

 

[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

 

[doodle]

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

 

[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

 

[m_niknam]

please send me a circuit diagram of termometer

 

[berkeman]

please send me a circuit diagram of termometer

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