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A student used a graphite pencil to shade in an area of graph paper - Edexcel - A-Level Physics - Question 1 - 2023 - Paper 3
Question 1
A student used a graphite pencil to shade in an area of graph paper. The thickness of the shading was uniform. She placed electrodes in contact with the graphite pe... show full transcript
Worked Solution & Example Answer:A student used a graphite pencil to shade in an area of graph paper - Edexcel - A-Level Physics - Question 1 - 2023 - Paper 3
Step 1
Step 2
Determine the percentage uncertainty in the measurement of R.
Answer
To determine the percentage uncertainty, we use the formula:
ext{Percentage uncertainty} = rac{ ext{Half resolution}}{ ext{Measurement}} imes 100.Given that the resolution is 0.001 MΩ and the measured resistance R is 0.289 MΩ, we calculate:
ext{Percentage uncertainty} = rac{0.0005 ext{ MΩ}}{0.289 ext{ MΩ}} imes 100 \\ = 0.173 \%Step 3
Describe how the student could determine an accurate value for the thickness of the graphite pencil shading. The method should use a suitable graph.
Answer
To determine the thickness of the graphite pencil shading accurately, the student can follow these steps:
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Measure Resistance: Use a ruler to measure the length between the electrodes and the width of shading. Measure the resistance R at various lengths of the shading.
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Plot a Graph: Create a graph of resistance (R) versus thickness (t) based on the collected data.
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Determine Gradient: Analyze the graph to determine the gradient, which is related to resistivity (ρ) by the equation:
where A is the cross-sectional area (related to thickness).
- Calculate Thickness: Rearranging this gives:
Step 4