Question

The correct combination of three resistances $1\Omega$, $2\Omega$ and $3\Omega$ to get equivalent resistance $\frac{11}{5}\Omega$ is

• A. All three are combines in parallel
• B. All three are combine in series
• C. $1\Omega$ and $2\Omega$ in parallel and $3\Omega$ is in series to both
• D. $2\Omega$ and $3\Omega$ are combined in parallel and $1\Omega$ is in series to both

Answer 1

Answer: (D)

According to option $2\Omega$ and $3\Omega$ are combined in a parallel combination. Hence equivalent resistance
$\frac{1}{R^{\prime }}=\frac{1}{2}+\frac{1}{3}=\frac{5}{6}$
$\therefore R^{\prime }=\frac{6}{5}$
$R^{\prime }$ is combined in series to $1\Omega$
$\therefore R_{eq}=R^{\prime }+1=\frac{6}{5}+1$
$=\frac{6+5}{5}=\frac{11}{5}\Omega$