AQA A Level Physics
AQA A Level Physics 3.1 Measurements and Practical Skills Exam Questions
Free AQA A Level Physics exam questions for 3.1 Measurements and Practical Skills, with a mark scheme for every pack. Covers SI units and prefixes, random and systematic errors, precision, accuracy, uncertainties, estimation, graph analysis and the required practicals.
3.1 Measurements and Practical Skills exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA A Level Physics 3.1 Measurements and Practical Skills
Measurements and their errors is AQA section 3.1 and underpins every part of the course. It covers SI base units and prefixes, homogeneity of equations, random and systematic errors, precision, repeatability, reproducibility, resolution and accuracy, absolute, fractional and percentage uncertainties, combining uncertainties, error bars and estimating physical quantities. Practical skills are tested throughout all papers, and Section A of Paper 3 focuses on practical skills and data analysis using the required practicals. Examiners ask you to propagate uncertainties, find gradients and intercepts with uncertainty from worst lines, suggest improvements to methods and judge whether data supports a relationship.
What you need to know
- 3.1.1 SI units The base units are kg, m, s, A, K and mol (candela is not required). Derive units of other quantities from base units, and use prefixes from tera to femto. Check equations for homogeneity.
- 3.1.2 Errors Random errors scatter readings either side of the true value and are reduced by repeats; systematic errors shift all readings the same way and are reduced by calibration or correcting zero errors. Know precision, repeatability, reproducibility, resolution and accuracy.
- 3.1.2 Uncertainties Absolute uncertainty is often half the resolution or half the range of repeats. When adding or subtracting, add absolute uncertainties; when multiplying or dividing, add percentage uncertainties; for a power, multiply the percentage uncertainty by the power.
- Graphs and error bars Draw error bars and a line of best fit plus a worst acceptable line. Uncertainty in gradient = (best gradient - worst gradient) / best gradient as a percentage. Linearise relationships, for example ln graphs for exponentials.
- 3.1.3 Estimation Estimate quantities to an appropriate order of magnitude using sensible values, such as the mass of a person or the number of molecules in a room.
- Required practicals AQA has 12 required practicals across the course, including stationary waves on a string, measuring g, the Young modulus, resistivity, emf and internal resistance, SHM, gas laws, capacitor charge and discharge, force on a wire, induced emf in a search coil and gamma inverse square law. Know methods, safety and analysis for each.
Common mistakes in 3.1 Measurements and Practical Skills
- Quoting results to too many significant figures. Match the number of significant figures to the least precise data used.
- Saying repeats reduce systematic error. Repeating and averaging only reduces the effect of random error; systematic error needs a change in method or calibration.
- Adding absolute uncertainties when multiplying quantities. For products and quotients, add percentage uncertainties.
- Drawing a worst line that does not pass through all the error bars. The worst acceptable line must still pass through every error bar, at the steepest or shallowest gradient.
- Writing vague improvements such as be more careful. Name a specific change, such as using a data logger, a fiducial marker or a micrometer instead of a ruler.
Try three 3.1 Measurements and Practical Skills exam-style questions
1. A resistor has a pd of 3.20 plus or minus 0.05 V and a current of 0.40 plus or minus 0.01 A. Calculate its resistance with its absolute uncertainty. (3 marks)
Show the mark scheme answer
R = 3.20 / 0.40 = 8.0 ohms; percentage uncertainty = 1.6 percent + 2.5 percent = 4.1 percent; absolute uncertainty = 0.041 x 8.0 = 0.3 ohms, so R = 8.0 plus or minus 0.3 ohms.
2. Explain the difference between a random error and a systematic error, giving an example of each. (4 marks)
Show the mark scheme answer
A random error causes readings to vary unpredictably around the true value; for example reaction time when starting a stopwatch; a systematic error shifts every reading by the same amount or proportion; for example a zero error on a micrometer.
3. A student measures the diameter of a wire once using a metre rule. Suggest two improvements to reduce the percentage uncertainty. (2 marks)
Show the mark scheme answer
Use a micrometer screw gauge with higher resolution (0.01 mm); take readings at several points and orientations along the wire and calculate a mean.
3.1 Measurements and Practical Skills FAQs
What does AQA A Level Physics 3.1 Measurements and their errors cover?
It covers SI units and prefixes, errors, precision and accuracy, uncertainties and how to combine them, graphs with error bars, estimation and the skills used in the required practicals.
Which paper tests measurements and practical skills?
Practical skills can be tested on any paper, and Section A of Paper 3 focuses specifically on practical skills and data analysis.
How do I revise the required practicals?
For each one, write down the method, the variables, the graph you would plot, what the gradient or intercept gives, the main sources of uncertainty and safety points. Then practise uncertainty calculations with real-looking data.
