**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 R_{1} is the resistance of Wire #1 and R_{2} is the resistance of Wire #2, then which of the following is true?

- A. R
_{2}= R_{1} - B. R
_{2}= R_{1} - C. R
_{2}= 6R_{1} - D. R
_{2}= 12R_{1}

**Correct Answer:** B

**Explanation:**

B The resistance of a wire is determined by R = so let's say R_{2} = . Because the diameter is doubled for Wire #1, the cross-sectional area is actually multiplied by a factor of 4. So,