Applying 2nd Kirchhoff's Law in a Circuit: Understanding its Use and Limitations

[Jhenrique]

Homework Statement

The 2nd Kirchhoff's law can be applied in this circuit twice (I think...):

The 1nd and 2nd:

And the my doubt is: is valid/correct try to apply the 2nd Kirchhoff's law in the mesh detached in red?

Homework Equations

The Attempt at a Solution

 

[ehild]

Yes, you can apply the 2nd Kirchhoff's for any two loops. And the red one is much simpler than the green one. But R3 and R5 can be replaced by their parallel equivalent, and then you have a single loop.

ehild

 

[Jhenrique]

So, the 2nd Kirchhoff's law applied in the red circuit will be: $v_3 + v_5 = 0$, correct!?

 

[BvU]

Correct. See the last picture in http://www.regentsprep.org/Regents/physics/phys03/bkirchof2/

 

[dauto]

You can always apply Kirchhoff's 2nd to any loop. Note though that the equations you will find won't always be independent from each other. In your example, the green, red, and blue loops produce only two independent equations.