MCAT Physics Question 78: Answer and Explanation
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Question: 78
3. The resistance of two conductors of equal cross-sectional area and equal lengths are compared, and are found to be in the ratio 1:2. The resistivities of the materials from which they are constructed must therefore be in what ratio?
- A. 1:01
- B. 1:02
- C. 2:01
- D. 4:01
Correct Answer: B
Explanation:
The resistance of a resistor is given by the formula
Thus, there is a direct proportionality between resistance and resistivity. Because the other variables are equal between the two resistors, we can determine that if R1:R2 is a 1:2 ratio, then ρ1: ρ2 is also a 1:2 ratio.