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
$R_{AB}=\frac{15R_1}{15+R_1}=6$
$\Rightarrow 15R_1-6R_1=15\times 6$
$\Rightarrow 9R_1=90$
$\Rightarrow R_1=10\Omega$