polarities in supernode

[PG1995]

Hi, :smile:

Please have a see on the following link:
https://img840.imageshack.us/img840/1959/img0002qc.jpg

Please have a look on the Figure 3.8 in bottom right corner. What defines the polarities of v3 and v2? Is it the directions of I3 and I2? Please tell me. Thank you

Cheers

 

[KerimF]

On this circuit, v2 and v3 are positive relative to the reference node (at the bottom). It is like saying v2 = v2 - Vref and v3 = v3 - Vref while Vref is assumed to be 0V.
So the original KVL equation is:
(Vref - v2) + 5 + (v3 - Vref) = 0
But since Vref=0, the equation can be simplified:
- v2 + 5 + v3 = 0

 

[PG1995]

Thanks, Karim.

1: So, the direction of I3 and I2 which defines the polarities?

2:

So the original KVL equation is:
(Vref - v2) + 5 + (v3 - Vref) = 0

Which figure did you use, Figure 3.7 or Figure 3.8, from the link in my first post to write the quoted equation? Are you traversing the loop CCW? Please let me know. Thank you for all the help.

Regards
PG