The equivalent resistance between points A and B in the given network is :

Solution

Physics sir · 2 steps

Start at the far left corner and fold the ladder towards B: each stage collapses to 5 Ω.

1. Read the network. Every 10 Ω resistor goes from A to a corner of the outer path. The outer path runs A, left corner, top-left, top-right, right, B, with a 5 Ω resistor on each segment. So this is a ladder, and you can reduce it one rung at a time, starting from the end farthest from B.

   Stage	Series part	Parallel with 10 Ω from A	Result
   Top-left corner	5 + 5 = 10 Ω (two left resistors)	10 ∥ 10	5 Ω
   Top-right corner	5 + 5 = 10 Ω (add top 5 Ω)	10 ∥ 10	5 Ω
   Right corner	5 + 5 = 10 Ω (add slanted 5 Ω)	10 ∥ 10	5 Ω
   Point B	5 + 5 = 10 Ω (add vertical 5 Ω)	10 ∥ 10 (bottom resistor)	5 Ω

   10 Ω ∥ 10 Ω = (10 × 10)/(10 + 10) = 5 Ω

2. So. The pattern repeats all the way to B, and the last step gives R_(AB) = 5 Ω, which is option (c).

The idea to keep. For a ladder network, begin at the end farthest from the terminals and fold inward: series, then parallel, then repeat. A repeating pattern often makes every stage give the same value.

Answer from the NTA final answer key. Solution by PrepWiser.