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KCET · Physics · Current Electricity

The equivalent resistance between the points \(A\) and \(B\) in the following circuit is

  1. A \(0.5 \Omega\)
  2. B \(5.5 \Omega\)
  3. C \(0.05 \Omega\)
  4. D \(5 \Omega\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(5.5 \Omega\)

Step-by-step Solution

Detailed explanation

Let \(x\) be the equivalent resistance of the
circuit, then

\(\therefore R_{A B}=x \)
\( \Rightarrow \frac{x \times 2}{2+x}+2+2=x \)
\( \Rightarrow \frac{2 x}{x+2}=x-4 \)
\( \Rightarrow 2 x=(x-4)(x+2) \)
\( \Rightarrow 2 x=x^2+2 x-4 x-8 \)
\( \Rightarrow x^2-4 x-8=0 \)
\( \Rightarrow \frac{-(-4) \pm \sqrt{(-4)^2-4 \times 1 \times(-8)}}{2 \times 1} \)
\( =\frac{4 \pm \sqrt{48}}{2}=\frac{4 \pm 4 \sqrt{3}}{2} \)
\( =2+2 \sqrt{3}=5.46 \Omega \approx 5.5 \Omega\)