JEE MAIN - Physics (2018 - 15th April Morning Slot - No. 25)
In the given circuit all resistances are of value $$R$$ $$ohm$$ each. The equivalent resistance between $$A$$ and $$B$$ is :
_15th_April_Morning_Slot_en_25_1.png)
$$2R$$
$$3R$$
$${{5R} \over 3}$$
$${{5R} \over 2}$$
Explanation
_15th_April_Morning_Slot_en_25_4.png)
Let us assume potential at point M is X volts. Now you can see a plain wire is directly connected between point N and point M so point N will also have same potential as point M.
Similarly, a plain wire is directly connected between point N and point O so point O will also have same potential as point N.
Also, a plain wire is directly connected between point O and point P so point P will also have same potential as point O.
Now you can see point P and point M both have same potential X, so no current will flow through that path so you can remove that resistor. Similarly, as point O and point M both have same potential X, so no current will flow through that path also so you can remove that resistor too.
So new circuit becomes
_15th_April_Morning_Slot_en_25_3.png)
$$ \therefore $$ RAB = R + R = 2R
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