AP Physics 1 Question 29: Answer and Explanation

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Question: 29

9. A wire is split into 4 segments, and they have resistances of R, 2R, ½R, and 4R in that order. Which of the following sets of changes from one segment to the next could correctly account for the changes in resistance?

R→2R    2R→4R    4R→R

  • A. length is doubled    area is doubled    radius is doubled
  • B. length is doubled    area is halved    radius is doubled
  • C. length is doubled    area is doubled    radius is quadrupled
  • D. length is halved    area is doubled    radius is doubled

Correct Answer: B

Explanation:

B The formula for resistance is R = . Keep in mind that Area = πr2, and the only answer that fits all three changes is (B).