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I'm confused in a basic concept in current electricity. Suppose I have two situations-

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In situation A, the points A and B are not necessarily equipotential. So a current can flow through the wire AB. But in this case, we can treat the resistor combinations(in series)-(R1,R2) and (R3,R4) to be in parallel. But in situation B, there is resistor R5 in branch AB, so the respective resistor combinations are not in parallel. Why does this happen, and why do they remain in parallel connection in A and not in B? Why does a resistor in branch AB in situation B make a difference?

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let us assume there is a potential difference across $A$ and $B$, then there is a current $i$ across it, now if you apply the formula $R$ $=$ $\cfrac{|V_{A}-V_{B}|}{I}$ you would get a resistance of conducting wire , which is not possible so a conducting wire must have equal potential across its terminals ( this is in ideal case)

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  • $\begingroup$ Since R1 and R4 have different values, therefore potential at A and B must have different values. How do you explain this? If A and B were to be equipotential, current would never have flown through the branch AB, but current does flow through AB. $\endgroup$
    – Abhinav Tahlani
    Commented Apr 20, 2020 at 8:03
  • $\begingroup$ @Abhinav Tahlani actually current through R1 and R4 have different values , but potential difference across them is same $\endgroup$
    – maverick
    Commented Apr 20, 2020 at 8:06
  • $\begingroup$ @Abhinav Tahlani I would make it easier ever seen hc verma lecture on current without potential difference search it on you tube $\endgroup$
    – maverick
    Commented Apr 20, 2020 at 8:07

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