WPH16 Practical Skills in Physics II

Lessons in WPH16

1. The Unit 6 practical skills paper: what changes at A2
   Same format as Unit 3, plus log graphs, compounding uncertainties, apparatus with details, inconsistent readings and precise use of accuracy, precision and sens
2. Precision, accuracy, resolution, sensitivity and validity
   Accuracy: close to the true value. Precision: repeats close together. Resolution: smallest interval. Sensitivity: output change per unit input change (a gradien
3. Planning at A2: apparatus, data loggers and calibration
   Name apparatus with useful details (range, resolution, size). Justify data loggers by high sampling rate, simultaneous readings or long duration. Calibrate agai
4. Planning from a given relationship
   Start from the formula: what you change, what you measure, the straight-line graph and what its gradient gives, how many readings over what range. For exponenti
5. Compounding percentage uncertainties
   Products and quotients: add percentages. Powers: multiply by the power (root: halve). Sums and differences: add absolute uncertainties first, then convert. Neve
6. The max/min method for uncertainty in a calculated value
   Max result: top quantities at their largest, bottom ones at their smallest; min the reverse. Uncertainty = (max - min) / 2. Do not round early; do not use max/m
7. Uncertainty in a gradient and an intercept
   Worst acceptable line through the spread of points. Gradient uncertainty = |worst - best| / best x 100%; intercept uncertainty = |worst - best|. Carry the perce
8. Logarithms for practical physics
   log is base 10 (inverse 10^x); ln is base e (inverse e^x). log(ab) = log a + log b; log aⁿ = n log a. Take logs of (quantity / unit). Give logs to a consistent
9. Log-log graphs and power laws
   y = kxⁿ gives log y = n log x + log k: plot log y against log x; gradient n (no unit), intercept log k, k = 10^c. Match the order with y = mx + c and say 'the
10. Log-linear graphs for exponential changes
    y = y_0 e^-kx gives ln y = -kx + ln y_0: gradient -k, intercept ln y_0 (y_0 = e^c). Half value = ln 2 / k. Use ln, not log, for e-based equations.
11. Reading intercepts, false origins and systematic errors
    Read the intercept only at x = 0; otherwise c = y - mx from a point on the line. Convert log intercepts with 10^c or e^c. Unexpected intercepts signal systemati
12. Implementation: criticising data and spotting inconsistent readings
    Check units by calculating and comparing. Name inconsistent readings and repeat them. Judge sufficiency by the number and range of readings. Know each component
13. Oscilloscopes, data loggers and sensors
    p.d. = divisions x y-gain; time = divisions x time base; measure over many divisions and cycles. Sampling interval much shorter than the change. Screen readings
14. Practical skills in core practicals 9 and 10
    CP9: v = card length / time, add percentages; friction-compensated runway; Δp against Δt has gradient F. CP10: overhead camera, scale in view, frames / frame ra
15. Practical skills in core practical 11
    ln V against t: gradient -1/RC, intercept ln V_0. RC is the time to 37%; half-time = RC ln 2. Compare with nominal RC within the tolerance. Discharge before han
16. Practical skills in core practicals 12 to 14
    CP12: stir, heat slowly, heat and cool; sensitivity = gradient of the calibration curve. CP13: control funnel and two-power method remove systematic losses. CP1
17. Practical skills in core practicals 15 and 16
    CP15: subtract background; long counts for random decay; fixed distance; ln C against x, gradient -μ, x_1/2 = ln 2 / μ; tongs and distance. CP16: find resonance
18. Evaluating experiments and conclusions at A2
    Limits from your own compounded uncertainty, compared explicitly with the accepted value. Systematic errors push results one way. Improve the largest uncertaint
19. Safety in A2 practicals
    Name the specific hazard in this experiment and a precaution that controls it. Capacitors: discharge, working p.d., polarity. Radioactive sources: tongs, distan

Next exams for WPH16

• January 2027: Mon 25 Jan 2027, morning, 1h 20m
• Summer 2027: Tue 8 Jun 2027, morning, 1h 20m

From Pearson's final timetables. All exam dates. Always confirm your entries with your exams officer.