A student carries out an experiment to determine the resistivity of a metal wire. She determines the resistance from measurements of potential difference between the ends of the wire and the corresponding current. She measures the length of the wire with a ruler and the diameter of the wire using a micrometer. Each measurement is made with an uncertainty of 1%. Which measurement gives the largest uncertainty in the calculated value of the resistivity?

A-Level AQA Physics Resistance & Resistivity: A student carries out an experim

A student carries out an experiment to determine the resistivity of a metal wire - AQA - A-Level Physics - Question 8 - 2018 - Paper 1

Question 8

A student carries out an experiment to determine the resistivity of a metal wire. She determines the resistance from measurements of potential difference between the... show full transcript

Worked Solution & Example Answer:A student carries out an experiment to determine the resistivity of a metal wire - AQA - A-Level Physics - Question 8 - 2018 - Paper 1

Step 1

A current

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Answer

The uncertainty in the current measurement does not significantly affect resistivity calculations because resistivity depends mainly on resistance, length, and area.

Step 2

B diameter

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Answer

The diameter measurement affects the cross-sectional area, which is critical in determining resistivity. Given the formula for resistivity, uncertainty in diameter has a substantial impact.

Step 3

C length

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Answer

The length measurement has a lesser impact because although it contributes directly, the influence of area governed by the diameter has greater significance in the overall calculation of resistivity.

Step 4

D potential difference

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Answer

Uncertainty in potential difference affects the resistance calculation, but the resistivity formula primarily relies on both length and cross-sectional area.

Step 5

Conclusion

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Among these options, the measurement that gives the largest uncertainty in the calculated value of resistivity is therefore B) diameter, as it impacts the area used in the resistivity formula more heavily than the other variables.

A student carries out an experiment to determine the resistivity of a metal wire - AQA - A-Level Physics - Question 8 - 2018 - Paper 1

Worked Solution & Example Answer:A student carries out an experiment to determine the resistivity of a metal wire - AQA - A-Level Physics - Question 8 - 2018 - Paper 1

A current

B diameter

C length

D potential difference

Conclusion

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