question_answer

A wire of resistance R is bent to form a square ABCD as shown in the figure. The effective resistance between E and C is: (E is mid-point of arm CD)             [JEE Main 9-4-2019 Morning]

A) \[R\]                            

B) \[\frac{1}{16}R\]

C) \[\frac{7}{64}R\]

D) \[\frac{3}{4}R\]

Correct Answer: C

Solution :

\[\frac{1}{{{R}_{eq}}}=\frac{8}{7R}+\frac{8}{R}\] \[\frac{1}{{{R}_{eq}}}=\frac{8+56}{7R}\] \[{{R}_{eq}}=\frac{7R}{64}\] Option [c]