Finding the battery voltages in this circuit

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SUMMARY

The discussion centers on calculating the battery voltages ε1 and ε3 in a given circuit. The correct value for ε1 is established as 3V. However, the user calculates ε3 to be 12V using Kirchhoff's second law, while the textbook states it should be 15V. The user questions the accuracy of the textbook, suggesting that the charge from point a to b may not be 3A, but others assert that this would violate Kirchhoff's current law.

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Eitan Levy
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Homework Statement


This circuit is given:[/B]
upload_2017-12-16_22-10-55.png

What are the values of ε1 and ε3?

Homework Equations


IR=V

The Attempt at a Solution


I get the right answer for ε1 (3V).
But I get that ε3=12V and not 15 (the answer in the textbook).
First the charge from a to b is 3A.
Then I simply use Kirchhoff's second law, which gives: 2Iab-6+10+2-ε3=0.
That gives ε3=12.
Am I wrong or the book? Maybe the charge from a to b is not 3A?
 

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Eitan Levy said:
Am I wrong or the book?
book is wrong
Maybe the charge from a to b is not 3A?
How could that POSSIBLY be true? If it were, then the currents into/out of node b would not add up to zero. A miracle.
 

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