Ans
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because for loop 1 you can see that current I is flowing across 3 ohms in direction opposite to direction we are considering that is from A to B clockwise... so we add 3ohm resistance but if you see for the 6ohm resistance the current I does not flow through that branch and plus A and B is open so we do not consider the potential drop across 6ohm as no current is flowing through it. hope this helps
6 years ago
by
ABHISHEK SHANKAR