Question

Three resistors of $3\Omega ,6\Omega$ and $2\Omega$ are connected together as shown in the figure given below. A resistance of $R\Omega$ is connected in parallel with the given network so that the effective resistance becomes $2\Omega .$ What is the value of resistance $R$?

• A. $11\Omega$
• B. $1\Omega$
• C. $4\Omega$
• D. $5\Omega$

Answer 1

The correct option is C $4\Omega$

$\text{Reg}=2\Omega$

$R_{BC}=3116=\frac{3\times 6}{3+6}=2\Omega$

$R_{AC}=2+2=4\Omega$

So,

$\text{Reg}=4\parallel R$

$2=\frac{4R}{4+R}$

$R=4\Omega$