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A uniform metal wire of length l has 10 Ω resistance. Now this wire is stretched to a length 2l and then bent to form a perfect circle. The equivalent resistance across any arbitrary diameter of that circle is

Asked in Re-NEET 2024 · Wires bent into shapes

• (1) 10 Ω
• (2) 5 Ω
• (3) 40 Ω
• (4) 20 Ω

Step-by-step solution

Why the other options are wrong

• (2) Forgets that stretching raises the resistance: (10)/2×1/2 uses the original 10 Ω ring.
• (3) This is the resistance of the stretched wire, 4×10, before it is bent into a circle.
• (4) This is one half of the ring, (40)/2; the two halves are in parallel across the diameter.

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