A metal wire of length l and diameter d has a resistance R. What would be the resistance of another wire of the same metal and of same length but having double the diameter?

  1. A. R
  2. B. R/4
  3. C. R/2
  4. D. 2R

Correct Answer: B. R/4

Explanation

Resistance R is inversely proportional to the cross-sectional area (A = \frac{\pi d^2}{4}). If the diameter d is doubled, the area increases by a factor of 4, meaning the new resistance becomes R/4.

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