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

  $4.5 \Omega$
• Correct answer
  C

  $4 \Omega$
• D

  $3 \Omega$

Solution

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 $(5+3) \Omega$ $\therefore \text { Net resistance }=\frac{(5+3)+(5+3)}{(5+3) \times(5+3)}=4 \Omega$

Hence, the correct answer is option: 'C'.