# how to mark polarities to write loop equations

Need a help to mark polarities to get loop equations or any other method get equations without marking polarities. simulate this circuit – Schematic created using CircuitLab

• I'm having trouble understanding what little you write, but more importantly, you say you "need help", but show no effort or own research. Which is a no-no to begin with, but specially so for what looks like it might be a homework question. – Asmyldof Jan 16 '16 at 11:04
• I tried and got some equations and I don't know those right or wrong. Anyway thanks! – Falcon Jan 16 '16 at 11:14

According to Passive sign convention, polarities are according to following scheme: Assuming directions of currents as in following images, we'll write following polarities while writing equations for different loops.

Equation: $$I_{1}R_{2} + (I_{1}-I_{2})R_{5} +(I_{1}-I_{3})(\frac{1}{sC_{1}} + R_{1}) = 0$$

Loop 2: Equation: $$I_{2}R_{4} + I_{2}\times{sL_{4}} + (I_{2}-I_{3})R_{3} +(I_{2}-I_{1})R_{5}=0$$ Loop 3: Equation: $$(I_{3}-I_{1})(\frac{1}{sC_{1}} + R_{1}) +(I_{3}-I_{2})R_{3}=E\times{sin(\omega t)}$$

• You're most welcome. :) – Saqib Ahmed Jan 16 '16 at 14:16
• We prefer not to supply complete homework answers to users - especially when they show no effort at a solution as in this case. Note that you don't have to take screen-grabs from CircuitLab schematics. You can save them directly into the post (and edit them later, if you need to). – Transistor Aug 8 '16 at 18:17
• @Transistor Got it. Thanks for the tips and advice. :) – Saqib Ahmed Aug 15 '16 at 12:07