Kirchoff's Law equation 3 unknowns Help

In summary, the given conversation is about solving an electrical circuit problem using Kirchoff's law. The equations for the three currents in the circuit are given and the person is asking for help in solving for the values of i1, i2, and i3. The conversation also includes a matrix representation of the equations and some steps for solving it.
  • #1
JonB
1
0
Please could somebody help me with this Kirchoff's law question with explanations/working out? I've been on it for hours and cannot see where I'm going wrong!

Q. An electrical circuit comprises three closed loops giving the following equations for the currents i1, i2 and i3.

i1 + 8i2 + 3i3 = -31
3i1 - 2i2 + i3 = -5
2i1 - 3i2 + 2i3 = 6

Solve for i1, i2 and i3

Any help appreciated!
 
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  • #2
We have
$$
\left[\begin{array}{rrr|r}
1 &8 &3 &-31 \\
3 &-2 &1 &-5 \\
2 &-3 &2 &6
\end{array} \right]_{\begin{array}{rr}-3R_1+R_2 \mapsto R_2 \\ -2R_1+R_3 \mapsto R_3\end{array}} \to
\left[\begin{array}{rrr|r}
1 &8 &3 &-31 \\
0 &-26 &-8 &88 \\
0 &-19 &-4 &68
\end{array} \right]_{-\frac{19}{26}R_2 + R_3 \mapsto R_3} \to
\left[\begin{array}{rrr|r}
1 &8 &3 &-31 \\
0 &-26 &-8 &88 \\
0 &0 &\frac{24}{13} &\frac{48}{13}
\end{array} \right].
$$
Can you finish?
 

FAQ: Kirchoff's Law equation 3 unknowns Help

1. What is Kirchoff's Law equation for 3 unknowns?

Kirchoff's Law equation for 3 unknowns is a mathematical representation of the principle of conservation of energy and charge in an electrical circuit. It states that the sum of the currents entering a junction is equal to the sum of the currents leaving the junction, and the sum of the voltage drops in a closed loop is equal to the sum of the voltage sources in the loop.

2. How do you apply Kirchoff's Law equation to solve problems with 3 unknowns?

To apply Kirchoff's Law equation to solve problems with 3 unknowns, you need to first draw a circuit diagram and label all the components and their corresponding values. Then, write down all the equations for each junction and loop in the circuit using Kirchoff's Law equation. Finally, solve the equations simultaneously to find the values of the unknowns.

3. Can Kirchoff's Law equation be used for circuits with more than 3 unknowns?

Yes, Kirchoff's Law equation can be used for circuits with any number of unknowns. However, as the number of unknowns increases, the equations become more complex and may require advanced mathematical techniques to solve.

4. What are the limitations of Kirchoff's Law equation for solving circuits?

Kirchoff's Law equation assumes that the components in the circuit are ideal, meaning they have no resistance or capacitance. In real-life circuits, there will always be some resistance and capacitance, which can affect the accuracy of the solutions obtained using Kirchoff's Law equation.

5. Are there any alternative methods for solving circuits with multiple unknowns?

Yes, there are alternative methods for solving circuits with multiple unknowns, such as using nodal analysis or mesh analysis. These methods may be more efficient and accurate for certain types of circuits, but they also have their own limitations and require a deeper understanding of circuit theory.

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