AP Physics 1 Question 47: Answer and Explanation

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Question: 47

2. Wire #1 has three times the length and twice the diameter of Wire #2. If both wires are made of the same material and if R1 is the resistance of Wire #1 and R2 is the resistance of Wire #2, then which of the following is true?

  • A. R2 = R1
  • B. R2 = R1
  • C. R2 = 6R1
  • D. R2 = 12R1

Correct Answer: B


B The resistance of a wire is determined by R = so let's say R2 = . Because the diameter is doubled for Wire #1, the cross-sectional area is actually multiplied by a factor of 4. So,