Required practicals and exam skills
Physics · GCSE · The School
What is examined
The practicals are examined on paper, so the method must be known in words. The standard set covers specific heat capacity, resistance of a wire, I–V characteristics, density, force and extension (Hooke's law), acceleration, waves in a ripple tank, light and reflection, and radiation and absorption. For each: equipment, steps in order, and the variable kept constant.
Uncertainty and figures
Every measurement has an uncertainty — half the smallest division on the scale is the usual estimate. A ruler to 1 mm gives ±0.5 mm. Quote answers to the same number of significant figures as your LEAST precise measurement; a calculator giving 4.283746 from data measured to 2 s.f. is claiming a precision you do not have.
Writing the long answer
Six marks wants a method someone else could follow: apparatus, the independent variable and its range, the dependent variable and how it is measured, the control variables, repeats and a mean, and safety WITH a reason. Add how the data will be processed — 'plot extension against force and take the gradient' — because that is often the mark everyone misses.
"Describe how to find the resistance of a wire." (1) Set up a circuit with the wire, an ammeter in series and a voltmeter across the wire. (2) Independent variable: length, from 10 cm to 100 cm in 10 cm steps. (3) Dependent: read current and voltage at each length. (4) Control: same wire, same diameter, same material; switch off between readings so it does not heat. (5) Repeat each length three times and take a mean. (6) Calculate R = V ÷ I and plot R against length. Six numbered steps, six marks.