A question about KVL.

[cocoloco]

Hi to everyone!

All I need is guide about how to encircle the circuit correctly with KVL if we have a current source/-es in loops. An example with my very weird circuit.

Whatever I did, I didn't achieve a correct results (or correct SLAE) when checked in EWB. Please help!

Well, I see:

I1's loop: 6*5+30-40+8*5+8*I4-10=0
I2's loop: 5*3+5*I3+20=0
I3's loop: 5*I3+5*3+20+4*I3+4*I4=0
I4's loop: 4*I4+4*I3-10+15*I4+15*I5+20+8*I4+8*5-10=0
I5's (the highest) loop: 40+7I5+15+10-10+15I5+15I4+20=0

What are my mistaces? How to make correct SLAE in such cases? Sorry for broken English.

 

[KeepItSimpleStupid]

To make it easier, draw the currents clockwise or counterclockwise where clockwise is positive.

One isn't even labeled. The largest drawn loop.

The 15 ohm resistor has to have difference current flowing through it e.g. (I*-I**)*7 ohms

When a components shares a loop, both currents flow through that component, usually one in the opposite direction.

Make in the direction of the arrow positive.

 

[JimB]

I will not give advice on circuit analysis at the moment, but I will advise that you redraw your circuit, as it stands it is horrible.

Lines kinked and squiggled all over the place, straighten them out.

Where you have two resistors or voltage sources in series, combine them to make things simpler.

Have a look at my version of your circuit:



JimB

 

[cocoloco]

yes , your version of my circuit is much better
well thanks for responces ! solved !

32x+15y+0z+0J4+0J5=-65
15x+27y+4z+0J4+8J5=0
0x+4y+9z+5J1+0J5=-20

32x+15y+0z=-65
15x+27y+4z=-40
0x+4y+9z=-35

x=-2,186
y=0.3311
z=-4,036

etc...