Practical Skills Flashcards
(58 cards)
What are the three key sections to include when writing an experimental method for AQA A-level Physics Paper 3?
- Independent and dependent variables: how they are measured and their range.
- Experimental technique: controlling variables, reducing uncertainty, repeating measurements.
- Graphical analysis: what graph to plot, how to linearize data, and extract values from gradient/intercept.
How should you define and measure the independent variable in an experiment?
Identify the variable deliberately changed. Use appropriate measuring devices, state its range (as large as safely possible), and ensure intervals yield at least five dependent variable data points.
How do you define and measure the dependent variable?
It’s the variable that changes in response to the independent variable. Use correct instruments and techniques to measure it with high resolution and low uncertainty.
What criteria determine a suitable range and interval for the independent variable?
The range must be large enough for trend detection but safe. The interval must give ≥5 data points to ensure reliable trend analysis and accurate graph plotting.
How should control variables be addressed in an experimental method?
Identify all control variables, describe how each is kept constant, and explain why controlling them is necessary for a valid experiment.
How can you reduce uncertainty in an experiment?
Repeat measurements until concordant results are achieved, average results, use high-resolution instruments, improve setup alignment, and reduce human error (e.g., parallax).
What does ‘concordance’ mean in the context of experimental data?
It refers to repeated measurements yielding consistent results, indicating high precision and reduced random error.
What must be included when describing graphical analysis in a method?
Specify what graph to draw (axes labels), how to manipulate variables to get a straight-line graph (e.g., squaring or inverting), relate it to y=mx+c, and state how the gradient/intercept gives the required value.
What features must a good experimental method have for full marks?
Clear structure, appropriate apparatus/technique, control of variables, justification of range, steps to reduce error, and details on how to process results graphically.
How should you respond to common weaknesses in experimental method questions?
Be specific: name devices, describe procedures clearly, explain repeats and averaging, define variable ranges, and explain how graphs yield desired quantities.
What distinguishes a systematic error from a random error?
Systematic errors consistently skew results in one direction (e.g., zero error); random errors vary unpredictably due to measurement imprecision.
How do systematic and random errors affect graphs?
Systematic errors shift the intercept but not the gradient. Random errors affect both the gradient and intercept, reducing the clarity of the trend line.
Give examples of systematic and random errors in measurement.
Systematic: a miscalibrated voltmeter or spring force meter. Random: parallax error (if inconsistent) or timing with human reaction.
How can you reduce each type of error?
Systematic: recalibrate or replace faulty equipment. Random: take repeated measurements, remove anomalies, and average results.
What is calibration, and how is it used to correct systematic error?
Measure a known standard, compare to the instrument’s reading, and apply a correction factor to future measurements.
What is percentage uncertainty and how can it be reduced?
Percentage Uncertainty = (Absolute Uncertainty / Measured Value) × 100%. Reduce it by decreasing the absolute uncertainty or increasing the size of the measured value.
What is the role of measurement resolution in experimental uncertainty?
Higher resolution (smaller scale divisions) reduces absolute uncertainty and improves precision of the measurement.
What makes experimental data ‘valid’?
It must test the intended hypothesis, with controlled variables, accurate measurement, and appropriate apparatus. Validity is limited to the measured range.
What is the difference between accuracy and precision?
Accuracy is closeness to the true value (affected by systematic error); precision is consistency among repeated values (affected by random error).
What are key safety and ethical considerations in experimental physics?
Ensure experiments don’t pose physical harm, use apparatus correctly, and avoid unethical practices (e.g., animal testing). Always state risk assessments where relevant.
What is an example of turning experimental data into a linear graph?
If investigating pendulum period T vs. string length L, plot T² against L to produce a straight line, allowing gradient to determine g.
How should you deal with anomalous results in an experiment?
Identify outliers that don’t fit the trend. Discard them if justified and based on experimental error, not bias. Repeat measurements to confirm trends.
How can video recording improve timing accuracy in mechanics experiments?
It eliminates reaction time error by allowing frame-by-frame analysis, often with a digital timer displayed in the background.
Why is it important to state the number of readings and range used in an experiment?
This ensures statistical reliability, supports pattern identification, and enables accurate graphical analysis.