MCQ
The equivalent resistance of the infinite network given below is :
  • A
    $2\,\Omega$
  • B
    $(1+\sqrt{2})\,\Omega$
  • $(1+\sqrt{3})\,\Omega$
  • D
    $(1+\sqrt{5})\,\Omega$

Answer

Correct option: C.
$(1+\sqrt{3})\,\Omega$
c
If effective resistance is $x$,

$\Rightarrow x=1+\frac{x \times 1}{x+1}+1$

$\Rightarrow(x-2)=\frac{x}{x+1}$

$\Rightarrow x^2-x-2=x$

$\Rightarrow x^2-2 x-2=0$

$\text { So, } x=\frac{2 \pm \sqrt{12}}{2}$

$=1 \pm \sqrt{3}\,\Omega$

neglecting negative value, $x =1+\sqrt{3}\,\Omega$

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