# Kirchhoff's Law for two circuits

Discussion in 'Homework Help' started by iPas, Dec 19, 2013.

1. ### iPas Thread Starter New Member

Dec 19, 2013
2
0
I got this

and i need to do formulas for
I Kirchhoff's law:
II Kirchhoff's law:
Circuit I:
II circuit:

i know it's very easy, but im just a beginner, so need a lot of help :/

2. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515

You have one circuit, which is the whole diagram you have posted.

This circuit has several loops. Can you identify all of them? I make it five loops.

Kirchoffs voltage law (often called KVL) is written for a particular loop so you can write up to 5 different KVL equations.

You need to number the loops in some way to be able to identify them and refer to them.

3. ### amilton542 Active Member

Nov 13, 2010
494
64
What makes you think it's two circuits?

You have a single circuit with two energy sources. If your analysis does not agree with the conversation of energy and charge, then it's a trip back to the drawing board.

A fundamental question for the sidenote:

Why does the sum of the voltage drops sum to zero around a closed loop?

[Hint] Think in terms of the definition of voltage.

4. ### iPas Thread Starter New Member

Dec 19, 2013
2
0
I'm trying to use google translator for some of the phrases, because no idea how to translate them myself, so that might be the problem... i think i need to make formulas for 2 of the loops.. my friend made me this picture to help http://i.imgur.com/fbtvbth.png unforthunalety hes not online anymore to help me further...

these are the 3 example formulas (NOT FOR MY CIRCUIT JUST AN EXAMPLE OF WHAT I NEED FOR MINE)
-I1+I2+I3=0
I1*(Ri1+R1)+I3*R3=E1
I1*(Ri1+R1)+I2*(Ri2+R2+R4)=E1+E2

5. ### amilton542 Active Member

Nov 13, 2010
494
64
You have a three dimensional linear vector space in three unkonwns. Because the circuit's linear, it agrees with the math (mostly).

One can be given an x amount of linear resistances with an x amount of succesive power sources, so don't be daunted by any given circuit.

Why can you construct a square linear system out of this mess?

6. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
I make it six.

7. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
Thank you for that correct, WBahn, I missed the one round the outside.

There are indeed six.

iPas, that just shows how easy it is to do.

On another note are you translating to English or from English?

AllAboutCircuits has an online textbook which tells you about Kirchoff and much besides.

See Chapter 6 here

8. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
The statements:

I Kirchhoff's law:
II Kirchhoff's law:
Circuit I:
II circuit:

Don't make any sense to us. It is almost certainly a language translation issue. So please try to describe fully what you are trying to do instead of just using compact phrases that obviously aren't translating well.