A powerful circuit

What is the total power of all of the resistors on the picture?

8 E 2 9 R \frac{8E^2}{9R} 8 E 2 3 R \frac{8E^2}{3R} 16 E 2 9 R \frac{16E^2}{9R} 24 E 2 R \frac{24E^2}{R}

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1 solution

Djordje Veljkovic
Jan 25, 2017

On the picture above, I have assumed the directions of the currents I 1 I_1 , I 2 I_2 , and I I . Using Kirchoff's First Law, we can see that I = I 1 + I 2 I = I_1 + I_2 . I have also marked points A and B. We can see that they have the same potentials, meaning that U a b = 0 U_ab = 0 . U a b U_ab can also be expressed as E E R I 2 R I 1 E - E - R*I_2 - R*I_1 , meaning that I_1 = I_2 = \(\frac{I}{2} ). U a b U_ab can also be expressed as E R I R I 1 + E E - R*I - R*I_1 + E . Switching I I with \(\frac{I_1}{2} ) gives us an equation from which we can express I 1 I_1 as \(\frac{2E}{3R} ), and that is also equal to I 2 I_2 . The total power is equal to the sum of all of the powers on the resistors, and is equal to 2*R*I_1^2 + R*I^2 = \(\frac{8E^2}{3R} ).

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