Practical Skills Flashcards

(58 cards)

1
Q

What are the three key sections to include when writing an experimental method for AQA A-level Physics Paper 3?

A
  1. Independent and dependent variables: how they are measured and their range.
  2. Experimental technique: controlling variables, reducing uncertainty, repeating measurements.
  3. Graphical analysis: what graph to plot, how to linearize data, and extract values from gradient/intercept.
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2
Q

How should you define and measure the independent variable in an experiment?

A

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.

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3
Q

How do you define and measure the dependent variable?

A

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.

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4
Q

What criteria determine a suitable range and interval for the independent variable?

A

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.

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5
Q

How should control variables be addressed in an experimental method?

A

Identify all control variables, describe how each is kept constant, and explain why controlling them is necessary for a valid experiment.

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6
Q

How can you reduce uncertainty in an experiment?

A

Repeat measurements until concordant results are achieved, average results, use high-resolution instruments, improve setup alignment, and reduce human error (e.g., parallax).

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7
Q

What does ‘concordance’ mean in the context of experimental data?

A

It refers to repeated measurements yielding consistent results, indicating high precision and reduced random error.

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8
Q

What must be included when describing graphical analysis in a method?

A

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.

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9
Q

What features must a good experimental method have for full marks?

A

Clear structure, appropriate apparatus/technique, control of variables, justification of range, steps to reduce error, and details on how to process results graphically.

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10
Q

How should you respond to common weaknesses in experimental method questions?

A

Be specific: name devices, describe procedures clearly, explain repeats and averaging, define variable ranges, and explain how graphs yield desired quantities.

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11
Q

What distinguishes a systematic error from a random error?

A

Systematic errors consistently skew results in one direction (e.g., zero error); random errors vary unpredictably due to measurement imprecision.

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12
Q

How do systematic and random errors affect graphs?

A

Systematic errors shift the intercept but not the gradient. Random errors affect both the gradient and intercept, reducing the clarity of the trend line.

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13
Q

Give examples of systematic and random errors in measurement.

A

Systematic: a miscalibrated voltmeter or spring force meter. Random: parallax error (if inconsistent) or timing with human reaction.

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14
Q

How can you reduce each type of error?

A

Systematic: recalibrate or replace faulty equipment. Random: take repeated measurements, remove anomalies, and average results.

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15
Q

What is calibration, and how is it used to correct systematic error?

A

Measure a known standard, compare to the instrument’s reading, and apply a correction factor to future measurements.

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16
Q

What is percentage uncertainty and how can it be reduced?

A

Percentage Uncertainty = (Absolute Uncertainty / Measured Value) × 100%. Reduce it by decreasing the absolute uncertainty or increasing the size of the measured value.

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17
Q

What is the role of measurement resolution in experimental uncertainty?

A

Higher resolution (smaller scale divisions) reduces absolute uncertainty and improves precision of the measurement.

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18
Q

What makes experimental data ‘valid’?

A

It must test the intended hypothesis, with controlled variables, accurate measurement, and appropriate apparatus. Validity is limited to the measured range.

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19
Q

What is the difference between accuracy and precision?

A

Accuracy is closeness to the true value (affected by systematic error); precision is consistency among repeated values (affected by random error).

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20
Q

What are key safety and ethical considerations in experimental physics?

A

Ensure experiments don’t pose physical harm, use apparatus correctly, and avoid unethical practices (e.g., animal testing). Always state risk assessments where relevant.

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21
Q

What is an example of turning experimental data into a linear graph?

A

If investigating pendulum period T vs. string length L, plot T² against L to produce a straight line, allowing gradient to determine g.

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22
Q

How should you deal with anomalous results in an experiment?

A

Identify outliers that don’t fit the trend. Discard them if justified and based on experimental error, not bias. Repeat measurements to confirm trends.

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23
Q

How can video recording improve timing accuracy in mechanics experiments?

A

It eliminates reaction time error by allowing frame-by-frame analysis, often with a digital timer displayed in the background.

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24
Q

Why is it important to state the number of readings and range used in an experiment?

A

This ensures statistical reliability, supports pattern identification, and enables accurate graphical analysis.

25
Why must you avoid vague statements like 'repeat and average' in exams?
They are too general. You must specify what is repeated, how many times, and why (e.g., to reduce random error in measuring time of oscillations).
26
What is accuracy in the context of measurements?
Accuracy refers to how close a measured result is to the true or accepted value.
27
What is precision in the context of measurements?
Precision describes how close repeated measurements are to one another, regardless of whether they are close to the true value.
28
Can measurements be precise but not accurate?
Yes. Repeated results may be close together (precise) but still far from the true value (not accurate).
29
Can a measurement be accurate but not precise?
Yes. A single measurement may be close to the true value (accurate), but repeated measurements vary widely (not precise).
30
What is the resolution of a measuring device?
It is the smallest increment of the measured quantity that the device can display.
31
How can precision be improved?
By taking multiple repeated measurements and removing anomalous results.
32
How can both accuracy and precision be improved?
By increasing the quantity measured—e.g., measuring 10 oscillations instead of one.
33
What are valid results in an experiment?
Results obtained by following a suitable procedure that directly answers the investigation’s question.
34
What does it mean for results to be repeatable?
The same experimenter obtains consistent results when repeating the experiment under the same conditions.
35
What does it mean for results to be reproducible?
Different experimenters obtain consistent results when performing the experiment using different methods or equipment.
36
What types of basic measuring instruments should you know?
Meter rules, balancers, protractors, stopwatches, ammeters, voltmeters.
37
What are examples of more precise instruments?
Micrometer screw gauges and vernier calipers.
38
What is parallax error and how is it avoided?
A reading error due to the observer’s line of sight not being perpendicular to the scale. It can be avoided by viewing directly from above or using a mirror.
39
What are the main parts of a micrometer?
Main scale (on the sleeve), thimble scale (rotating part), spindle, anvil, and ratchet.
40
How do you take a micrometer reading?
Add the main scale reading (0.5 mm per division) to the thimble scale reading (0.01 mm per division).
41
What is the function of the ratchet on a micrometer?
To prevent over-tightening, ensuring consistent clamping force and avoiding damage or zero error.
42
What is a zero error in a micrometer?
When the jaws are closed but the reading is not zero. Subtract it if it’s positive; add it if it’s negative.
43
What can vernier calipers measure?
External diameters, internal diameters, lengths, and depths.
44
How do you read a vernier caliper?
Add: Whole cm from the main scale. Whole mm from the main scale. Tenths of a mm from the vernier scale (where the scales align).
45
How does a vernier scale increase accuracy?
It adds an extra significant figure by subdividing the smallest main scale division.
46
How does a dial caliper work?
Each dial rotation corresponds to 1 mm; the dial is divided into 100 parts (each 0.01 mm).
47
Example: A reading of 12 mm on the fixed scale and 25 on the dial gives what total?
12.25 mm.
48
What is the full-scale deflection in an analogue meter?
The maximum value the meter can measure.
49
What is the interval on an analogue meter?
The difference between adjacent scale markings.
50
How is parallax error minimized in analogue meters?
By using a mirror behind the pointer and aligning the pointer with its reflection.
51
What is absolute uncertainty?
The numerical range of error in a measurement, accounting for instrument resolution and technique.
52
What is percentage uncertainty?
The absolute uncertainty expressed as a percentage of the measured value.
53
How should uncertainty be reported?
As: measured value ± uncertainty (e.g., 2.5 ± 0.1 V).
54
When should percentage uncertainty be calculated?
Only when specifically requested.
55
What contributes to overall uncertainty?
Instrument resolution, manufacturer tolerance, experimenter judgment, experimental procedure, and available increments.
56
What are the four methods of calculating uncertainty?
From device resolution. From experimental technique. From stated values. From variation in readings.
57
What is a reading?
A value obtained from a single judgment (e.g., reading a balance once).
58
What is a measurement?
A value obtained from two judgments (e.g., measuring the length of a wire from start to end).