Question

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

• A. $20 \, \Omega $
• B. $10 \, \Omega $
• C. $5 \, \Omega $
• D. $25 \, \Omega $

Answer 1

Answer: (B)

Here $2 \Omega$ and $3 \Omega$ resistances are short circuited, so circuit can be reduced as
$R_{A B} =\frac{15 R_{1}}{15+R_{1}}=6$
$\Rightarrow 15 R_{1}-6 R_{1} =15 \times 6$
$\Rightarrow 9 R_{1} =90$
$\Rightarrow R_{1}=10\, \Omega$