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Problem: I need to calculate a power balance, to check that i have found the correct currents.

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I have found that:

\begin{cases} I_{1}=-2.571 \\ I_{2}=-1.244 \\ I_{4}=1.755 \\ I_{6}=0.42 \end{cases}

The task is to calculate power balance and check it:

I do it using this formula:

$$R_{1} \cdot I_{1}^2+R_{2} \cdot I_{2}^2+R_{3} \cdot I_{2}^2+R_{4} \cdot I_{4}^2+R_{5} \cdot I_{general}^2+R_{6} \cdot I_{6}^2 = E \cdot I_{2}+U_{general}I_{general}$$

\$R_{1} \cdot I_{1}^2+R_{2} \cdot I_{2}^2+R_{3} \cdot I_{2}^2+R_{4} \cdot I_{4}^2+R_{5} \cdot I_{general}^2+R_{6} \cdot I_{6}^2\$ = 727 Watts

Update:

\$U_{general}=-R_{5} \cdot 3A+R_{2} \cdot I_{2}-8+R_{3} \cdot I_{2}+R_{1} \cdot I_{1}=0\$

\$U_{general} = 245.91 Volts\$

  1. \$E \cdot I_{2}^2 = 12.38 Watt\$ and \$U_{general} \cdot 3=737 Watt\$

Sum of power of sources = \$737+12.38= 749.38\$

  1. Consumed power = 727 Watts

Given 3% of inaccuracy, which is 22 Watts, I guess that I solved it right, didn't I?

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  • \$\begingroup\$ I think your first problem is that you have an answer in volts, and power is measured in watts. Why not determine the power at each component and sum them, rather than writing down one honkin' big impenetrable formula. \$\endgroup\$
    – Neil_UK
    Commented Mar 22, 2017 at 8:08
  • \$\begingroup\$ @Neil_UK, Yeah, I should have used watts for measuring power, my bad, I wrote an update. \$\endgroup\$
    – Viktor K
    Commented Mar 22, 2017 at 10:26

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