Question

Seven resistors are connected as shown in the diagram.


The equivalent resistance in ohms of this network between A and B is

• A. $20\Omega$
• B. $12\Omega$
• C. $8\Omega$
• D. $6\Omega$

Answer 1

The correct option is D $6\Omega$

After rearranging,

$\frac{30\times 6}{36}=5\Omega =P$


$\frac{P}{Q}=\frac{5}{4};\frac{R}{5}=\frac{10}{8}=\frac{5}{4}$

So its is a balnaced wheatkone bridge, $\frac{40}{9}\Omega$ inactive.

$R^{\prime }=\frac{(P+Q)(R+S)}{P+Q+R+S}$

$=\frac{\left(9\right)\left(18\right)}{5+4+10+8}=\frac{9\times 18}{27}$

$R^{\prime }=6\Omega$