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Flashcards · H556 · Topic 1

Development of practical skills in physics flashcards

15 cards on Topic 1, subtopics 1.1 to 1.2. Pick a subtopic or study them all.

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1.1 Practical skills assessed in a written examination

Accurate (results)
Close to the true value.
Precise (results)
Repeat readings agree with each other. A miscalibrated instrument gives precise but inaccurate readings.
Repeatable vs reproducible
Repeatable: the same result with the same method and the same person. Reproducible: the same result with a different method or person.
Control variable vs control experiment
A control variable is kept constant. A control experiment is a parallel run with the independent variable absent, showing the effect is caused by the factor being tested.
What do repeat readings improve, and what do they not fix?
They reveal anomalies and reduce the effect of random error on the mean. They do nothing for a systematic error, which needs recalibration or zeroing.
Pendulum: what do you plot to find g, and how do you get g from the gradient?
Plot T² against l: a straight line through the origin with gradient 4π²/g, so g = 4π² ÷ gradient.
How should a gradient be measured from a straight-line graph?
With a large triangle spanning most of the line, taking coordinates from the line itself, not from individual data points.
Give two specific improvements to a timing experiment, with reasons
Use light gates rather than a stopwatch, to remove human reaction time. Time many oscillations and divide, or measure a larger quantity, to reduce the percentage uncertainty.

1.2 Practical skills assessed in the practical endorsement

How is the Practical Endorsement assessed and reported?
Teacher assessed and reported separately; it does not contribute to the A level grade. At least 12 practical activities covering PAG1 to PAG12, plus consistent display of the CPAC.
The five CPAC competencies
1. Follows written procedures. 2. Applies investigative approaches and methods with instruments and equipment. 3. Safely uses a range of practical equipment and materials. 4. Makes and records observations. 5. Researches, references and reports.
Steps in a specific risk assessment
Name the hazard; say what could be harmed and how; state a specific control measure; say what to do if something goes wrong.
How do you read a micrometer correctly?
Note the zero error with the jaws closed. Close on the object using the ratchet only. Read the sleeve (including any half-millimetre mark), add the thimble reading, subtract the zero error. Repeat at other positions and average.
Reading an oscilloscope: peak voltage and frequency
Peak-to-peak divisions × V/div, halved, gives the peak value. Divisions for one cycle × time/div gives T; then f = 1/T.
Counting radiation: corrected count rate and the uncertainty in a count
Corrected count rate = source count rate − background count rate (background measured separately with no source). Uncertainty in N counts is about √N.
What is a fiducial marker and where is it placed for an oscillation?
A fixed reference mark for starting and stopping timing. Place it at the equilibrium position, where the object moves fastest, so timing is most consistent.

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