A uniform metallic wire length l has 10 Ω resistance. It is stretched to 2l and bent into a perfect circle. Equivalent resistance across a diameter of this circle is:
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Question

A uniform metallic wire length l has 10 Ω resistance. It is stretched to 2l and bent into a perfect circle. Equivalent resistance across a diameter of this circle is:

G1 Physics · Accepted Answer

Step 1: Stretching to double length (fixed volume) makes total wire resistance R′ = 4R = 40 Ω. Step 2: A diameter divides circular wire into two equal 20 Ω semicircular sections in parallel. Step 3: R(eq) = 20||20 = 10 Ω.