What is the correct way to apply Kirchhoff's rules to this circuit?

In summary, the conversation discusses applying Kirchhof's rules to a circuit with known resistors and voltages. The first image shows the correct equations to find the currents i, i1, and i2. The second image introduces two new currents, ia and ib, and the question is asked if the equations for these currents are correct. It is noted that the junction rule should be applied before writing any equations to simplify the problem.
  • #1
kliker
104
0
[PLAIN]http://img17.imageshack.us/img17/201/73448266.jpg

let's suppose that we know all resistors and voltages

by applying kirchhof rules we have

V1 - i*R1 - i*R2 -i2*R3 = 0
V1 - i*R1 - i*R2 - i1*R4 - V2 = 0
-V2 + i2*R3 - i1*R4 = 0

we know V1,V2,V3 R1,R2,R3 and we can find the currents

now we have this image

[PLAIN]http://img220.imageshack.us/img220/4225/53762410.jpg

it's the same circuit and we suppose that there are two currents ia and ib

now here we have this, is this right?

V1 = ia*R1 + ia*R2 - ib*R2
-V2 = ib*R4 + ib*R3 - ia*R3

is this correct? but if we find ia and ib, we know just two currents, I mean in the previous image we have 3 currents, i i1 and i2

here in the second image if these equations are correct we get the current ia which is the current i and ib which is the current i1

but we don't have only these 2 currents we have a third current too called i2, how can I find it here?

thanks in advance
 
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  • #2
I don't know what the second image is about but the first one looks correct, except you didn't apply the junction rule, so you won't be able to solve it until you do.

It's worth noting that you should always try to apply the junction rule before you start writing any equations as it greatly simplifies things.
 

Related to What is the correct way to apply Kirchhoff's rules to this circuit?

What are Kirchhoff's rules?

Kirchhoff's rules, also known as Kirchhoff's laws, are two fundamental principles in circuit analysis that govern the behavior of electric circuits. These rules are named after German physicist Gustav Kirchhoff and are essential for understanding and analyzing complex circuits.

What is Kirchhoff's first rule?

Kirchhoff's first rule, also known as the junction rule, states that the sum of currents entering a junction in a circuit must be equal to the sum of currents leaving the junction. In other words, the total current flowing into a junction must equal the total current flowing out of the junction.

What is Kirchhoff's second rule?

Kirchhoff's second rule, also known as the loop rule, states that the algebraic sum of the voltage drops around any closed loop in a circuit must be equal to zero. This means that the sum of the voltages gained and lost in a closed loop must be equal to zero.

How do Kirchhoff's rules help in circuit analysis?

Kirchhoff's rules are used in circuit analysis to determine the current, voltage, and resistance in a circuit. By applying these rules, we can solve for unknown values and understand how the components in a circuit are connected and interact with each other.

Are Kirchhoff's rules always accurate?

Kirchhoff's rules are based on the laws of conservation of charge and energy and are always accurate when applied correctly. However, they may not work in certain cases such as non-linear circuits or circuits with changing magnetic fields. In these cases, more advanced methods may be required for accurate analysis.

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