.ocr.org.uk/Images/705129-equation-sheet-physics-a.pdf","initialIndex":39,"initialQuestionWindow":[{"id":"8b4a0422-22b9-42b3-a7d0-5b31e1353512","revisionId":"41e5eb62-599d-446f-805d-e3cec83d6226","questionNumber":null,"questionType":"LA","specification":"A student completes an experiment to find the electrical resistivity of a constantan wire.\n\n![Experimental setup for measuring resistivity](https://assets.mathsgenie.co.uk/aqa-qb/6474c4e2-5448-4479-a1f6-4023396c28d2.png)\n\nShe measures the resistance of different lengths of a constantan wire with a constant cross-sectional area of $2.0 \\times 10^{-7}\\text{ m}^2$ using a digital ohmmeter. She then calculates the resistivity of the constantan.\n\n| Attempt | Length ($\\text{m}$) | Measured Resistance ($\\Omega$) | Calculated Resistivity ($10^{-7}\\ \\Omega\\text{ m}$) |\n| :---: | :---: | :---: | :---: |\n| **1** | $0.20$ | $0.52$ | $5.2$ |\n| **2** | $0.40$ | $1.08$ | $5.4$ |\n| **3** | $0.80$ | $2.24$ | $5.6$ |","difficulty":7,"difficultyBand":"medium","totalMarks":11,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"1be8ed61-5b9f-4692-98e4-a2299107cbcd","label":"a","content":"Calculate the **mean** resistivity of the constantan wire.","markscheme":"- Computes mean resistivity: $\\frac{5.2 + 5.4 + 5.6}{3} \\times 10^{-7}$ M1\n- States final answer of $5.4 \\times 10^{-7}\\ \\Omega\\text{ m}$ (or $5.4 \\times 10^{-7}$) A1","marks":2,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"calculate_mean","label":"Calculate the mean","steps":[{"type":"text","order":0,"title":"Select the readings","content":"Use the three values already given in the **Calculated Resistivity** column: $5.2$, $5.4$ and $5.6$. They are all in units of $10^{-7}\\ \\Omega\\text{ m}$, so this common factor can stay outside the mean calculation.","highlights":[{"text":"Calculate the **mean** resistivity of the constantan wire.","location":"specification"}]},{"type":"hyper_latex","block":{"nodes":[{"latex":"\\text{mean resistivity}=\\frac{5.2+5.4+5.6}{3}\\times10^{-7}\\ \\Omega\\text{ m}"},{"latex":"\\text{mean resistivity}=\\htmlData{anchor=answer}{5.4\\times10^{-7}\\ \\Omega\\text{ m}}"}],"highlights":[{"color":"green","style":"box","anchor":"answer"}]},"order":1,"title":"Calculate the mean","description":"Add the three readings and divide by the number of readings, three. This calculation earns the first mark."}]}],"generatedAt":"2026-07-22T09:16:12.269Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]},{"id":"e7aa9a06-897b-4a06-a642-3a9993fec27f","label":"b","content":"Describe the conclusions that can be drawn from the data.","markscheme":"- Identifies that the calculated resistivity increases as the length of wire increases B1\n- Identifies that measured resistance increases as the length of wire increases B1\n- Notes that all calculated resistivity values are close (within $10\\%$, ranging from $5.2 \\times 10^{-7}$ to $5.6 \\times 10^{-7}\\ \\Omega\\text{ m}$) or that the experiment was repeated 3 times B1","marks":3,"order":1,"markingRubric":null,"explanation":{"methods":[{"id":"read_the_table","label":"Read the data","steps":[{"type":"text","order":0,"title":"Track the changing length","content":"Compare the rows in order. The wire length increases from $0.20\\ \\text{m}$ to $0.40\\ \\text{m}$ to $0.80\\ \\text{m}$, and the calculated resistivity rises from $5.2 \\times 10^{-7}\\ \\Omega\\text{ m}$ to $5.4 \\times 10^{-7}\\ \\Omega\\text{ m}$ to $5.6 \\times 10^{-7}\\ \\Omega\\text{ m}$.\n\nSo state: **the calculated resistivity increases as the length of wire increases.** This is the first conclusion and earns **B1**.","highlights":[{"text":"She then calculates the resistivity of the constantan.","location":"specification"}]},{"type":"text","order":1,"title":"Compare the resistances","content":"Now read the measured-resistance column for the same increasing lengths: it rises from $0.52\\ \\Omega$ to $1.08\\ \\Omega$ to $2.24\\ \\Omega$.\n\nTherefore: **the measur

Trial	Period $T$ (s)
1	1.83
2	1.79
3	1.86
4
5	1.80
Mean	1.81

Trial	Period $T$ (s)
1	1.83
2	1.79
3	1.86
4
5	1.80
Mean	1.81

Practical skills

Question 24

Practical skills Questions

Practical skills

Question 24

Practical skills Questions