The equivalent resistance between $A$ and $B$ is $6 \Omega$. The value of $R_1$ is

The equivalent resistance between $A$ and $B$ is $6 \Omega$. The value of $R_1$ is
  1. $20 \Omega$
  2. $10 \Omega$
  3. $5 \Omega$
  4. $25 \Omega$

Solution

Here $2 \Omega$ and $3 \Omega$ resistances are short circuited, so circuit can be reduced as $ \begin{array}{rlrl} & & R_{A B} & =\frac{15 R_1}{15+R_1}=6 \\ \Rightarrow & 15 R_1-6 R_1 & =15 \times 6 \\ \Rightarrow & 9 R_1 =90 \\ \Rightarrow & R_1 =10 \Omega \end{array} $

Asked in: AP EAMCET 2018 (22 Apr Shift 1)

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