Practical Skills

Master the experimental techniques, data handling, and measurement skills essential for OCR Module 1 -- from planning investigations to analysing results.

Spec Points Covered
  • I can identify independentThe variable that is deliberately changed by the experimenter., dependentThe variable that is measured as the outcome of the experiment., and control variablesVariables that must be kept constant to ensure a fair test. in an experiment.
  • I can design experiments with appropriate apparatus and techniques based on the underlying physics.
  • I can use common measuring instruments including stopwatches, light gates, rulers, calipers, micrometers, and digital multimeters.
  • I can read and interpret a micrometerA precision instrument with 0.01 mm resolution, used to measure small thicknesses and diameters. and vernier caliperA measuring instrument with 0.1 mm resolution, using a sliding vernier scale alongside a main scale. correctly.
  • I can set up electrical circuits correctly, connecting ammeters in series and voltmeters in parallel.
  • I can use an oscilloscopeAn instrument that displays voltage waveforms on a screen, allowing measurement of voltage, time period, and frequency. to measure voltage, time period, and frequency of a.c. signals.
  • I can follow laser safety procedures and explain the precautions needed when using ionising radiation.
  • I can distinguish between precisionHow close repeated measurements are to each other. A precise set of results has a small spread. and accuracyHow close a measurement is to the true or accepted value., and between random and systematic errors.
  • I can calculate percentage uncertaintyThe uncertainty expressed as a percentage of the measured value: (uncertainty / value) x 100%. and combine uncertainties for addition, subtraction, multiplication, division, and powers.
  • I can apply significant figure rules and use appropriate SI units with correct prefixes.
  • I can plot graphs with appropriate scales, draw lines/curves of best fit, and calculate gradients and intercepts.
  • I can suggest improvements to experimental methods to increase accuracy and reduce errors.
Notes
01 Experimental Design Variables, hypotheses, planning investigations → 02 Measuring Instruments Stopwatches, light gates, digital instruments → 03 Calipers, Micrometers & Vernier Scales Reading micrometers and vernier calipers, zero errors → 04 Electrical Equipment & Circuits Circuit construction, oscilloscopes, signal generators → 05 Lasers, Radiation & Safety Laser safety, radiation detectors, Geiger counters → 06 Precision, Accuracy & Errors Random vs systematic errors, zero errors, resolution → 07 Uncertainties & Error Analysis Absolute and percentage uncertainties, combining uncertainties → 08 Significant Figures & Units Significant figures rules, SI units, prefixes, standard form → 09 Graphs & Data Analysis Plotting graphs, gradients, intercepts, lines of best fit → 10 Improving Experiments Reducing errors, fiducial markers, repeats, evaluation →
Σ Key Equations Full Reference →
On Data Sheet
Not on Data Sheet
Percentage uncertainty
$$\% \text{ uncertainty} = \frac{\Delta x}{x} \times 100\%$$
Converts an absolute uncertainty to a percentage. Essential for combining uncertainties in products and quotients.
Percentage difference
$$\% \text{ difference} = \frac{|x_{\text{exp}} - x_{\text{acc}}|}{x_{\text{acc}}} \times 100\%$$
Used to compare your experimental result with an accepted value. If % difference < % uncertainty, the result is consistent.
Combining uncertainties (add/subtract)
$$\text{If } y = a \pm b: \quad \Delta y = \Delta a + \Delta b$$
When quantities are added or subtracted, add their ABSOLUTE uncertainties.
Combining uncertainties (multiply/divide)
$$\text{If } y = ab \text{ or } y = \frac{a}{b}: \quad \%\Delta y = \%\Delta a + \%\Delta b$$
When quantities are multiplied or divided, add their PERCENTAGE uncertainties.
Power rule for uncertainties
$$\text{If } y = a^n: \quad \%\Delta y = n \times \%\Delta a$$
Multiply the percentage uncertainty by the power. For $y = a^2$, the % uncertainty doubles.