LEARN MORE REMARKS The fact that I 2 and I 3 are both negative indicates that th

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REMARKS The fact that I2 and I3 are both negative indicates that the wrong directions were chosen for these currents. Nonetheless, the magnitudes are correct. Choosing the right directions of the currents at the outset is unimportant because the equations are linear, and wrong choices result only in a minus sign in the answer.

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Find the three currents in figure b, where R = 2.1 . (Note that the direction of one current may have been chosen wrongly!)

There are many chances for algebraic errors in this problem. Go back and check your work carefully.A

Explanation / Answer

In figure a

14 + 10 = 4I2 + 6I1

and   10 = 6I1 + 2(I1 - I2 )

=>   solving these equations

I1 = 2 A

I2 = 3 A

I3 = 1 A

In figure b

5 = I2 + 2.1 (I2 - I1)

5 - 5 = I2 + I1

=> I2 = 0.961 A

=> I1 = - 0.961 A      (   Direction is opposite to the direction specified)

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