Question

Eight identical resistamce r each are connected along edges of a pyramid having square base ABCD as shown. Calculate equivalent resistance between A and O

• A. $\frac{9r}{15}.$
• B. $\frac{7r}{15}.$
• C. $\frac{8r}{15}.$
• D. $\frac{10r}{15}.$

Answer 1

The correct option is B $\frac{7r}{15}.$

So, $R_{eq}=(r+\frac{r}{2})||\left(\frac{r}{2}\right)$

$=\left(\frac{3r}{8}\right)$

$R_{AO}=r||(\frac{r}{2}+\frac{3r}{2})$

$=\frac{7r}{15}$