YACQT (yet another circuit question thread)

[RESmonkey]

http://img530.imageshack.us/my.php?image=madnesshz5.jpg

I don't know how to include the Current Source in my calculations.

 

[esun]

How about this:

- I_1 + V_c/R_3 = I_s

Just use KCL: currents at a node must sum to zero.

 

[slackwarelinux]

Couldn't you do a source transform on the current source and turn it into a voltage source?
awesome paint picture

 

[bobsmith1492]

Originally posted by: esun
How about this:

- I_1 + V_c/R_3 = I_s

Just use KCL: currents at a node must sum to zero.

Yeah, use KCL for everything. If you know the node voltages, turn them into currents by doing (V1-V2)/R. Just make sure to keep all your polarities lined up.

 

[RESmonkey]

Originally posted by: esun
How about this:

- I_1 + V_c/R_3 = I_s

Just use KCL: currents at a node must sum to zero.

How do you know the direction of V_c/R_3 current?

Couldn't you do a source transform on the current source and turn it into a voltage source?

what?

 

[TecHNooB]

-Vs + I1 x (R1+R2) + (I1+Is) x R3 = 0

There's a lot of ways to solve for I1. esun's way is correct also.

 

[RESmonkey]

Originally posted by: slackwarelinux
Couldn't you do a source transform on the current source and turn it into a voltage source?
awesome paint picture

wait, how does a resistor in parallel w/ a current source turn into a voltage source?

 

[slackwarelinux]

Originally posted by: RESmonkey

Originally posted by: slackwarelinux
Couldn't you do a source transform on the current source and turn it into a voltage source?
awesome paint picture

wait, how does a resistor in parallel w/ a current source turn into a voltage source?

My drawing was pretty bad, but it turned into a voltage source in series with a resistor.



source transformations, taught by a professor who sounds like kermit the frog

start at around 1:22 for the source transforms

 

[frostedflakes]

Yeah since you have the node voltages, all you should need to use is Ohm's law and P=IV

For example, I1 is the current through R1, so I1=(Va-Vb)/R1=-0.476mA

 

[RESmonkey]

I think I understand now; the current source just injects current for R3. I wrote a KVL and am gonna try and solve it.

 

[RESmonkey]

GOT IT! Thanks guys.

 

[XZeroII]

There have been that many circuit questions before?