Question

The equivalent resistance between A and B is :

• A. $32.5\Omega$
• B. $22.5\Omega$
• C. $2.5\Omega$
• D. $42.5\Omega$

Answer 1

The correct option is B

$22.5\Omega$

Observe the following series combination of resistances

15 and adjacent 10 ohm in series

40 and adjacent 10 ohm in series

30 and adjacent 20 ohm in series

All the above stated series combinations are connected across point C and D i.e. across same potential difference. Therefore all these series combinations are in parallel to each other. Net resistance of this parallel combination comes out to be 12.5 ohms.

Now 12.5, 2 (connected across A and C) and 8(connected across D and B) ohms are in series with each other therefore total resitance aross A and B comes out to be 22.5 ohms.