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If a wire of uniform cross-section, length l, and resistance R is bent into a complete circle, the resistance between two diametrically opposite points is

1. 4R
2. 8R
3. R/4
4. 2R

Correct answer: R/4

Solution

When the wire is bent into a circle, the two diametrically opposite points divide it into two equal semicircles. Each semicircle has resistance R/2, and these two equal resistances are in parallel, giving R/4.

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