Question

Seven resistance are connected between points $A$ and $B$ as shown in adjoining figure. The equivalent resistance between $A$ and $B$ is

• A. $5\Omega$
• B. $4.5\Omega$
• C. $4\Omega$
• D. $3\Omega$

Answer 1

Answer: (C)

The equivalent circuit of the given circuit is

This is a balanced Wheatstone bridge. Therefore, the arm CD becomes in effective. Hence 5$\Omega$ and 3$\Omega$ are in series and they together are in parallel with (5 + 3) $\Omega$
$\therefore$ Net resistance $=\frac{\left(5+3\right)+\left(5+3\right)}{\left(5+3\right)\times \left(5+3\right)}=4\Omega$