OCR A-Level Physics practical endorsement: A complete PAG guide

OCR A-Level Physics A (H556) splits practical work into two separate assessments. The Practical Endorsement is a Pass/Not Classified result your teacher awards over the two years of the course. The practical-skills questions on the three written papers are the ones that actually count towards your A*-E grade. These are often conflated. The endorsement is reported alongside the grade on your certificate but doesn't contribute to it.

This guide covers OCR A (H556). If you're sitting OCR Physics B Advancing Physics (H557), the practical structure is different, so check the spec code on your timetable before using this.

The hands-on work is organised into 12 Practical Activity Groups, or PAGs (Practical Activity Groups). These are technique and apparatus clusters rather than fixed experiments: your school picks the activity within each PAG as long as the group's techniques are covered. The piece below walks through every PAG, explains how CPAC (Common Practical Assessment Criteria) assessment works, and shows how practical content shows up in the written papers.

A Practical Activity Group is a bundle of apparatus and techniques rather than one specific experiment. PAG1 'Investigating motion', for example, might be stopwatches with trolley experiments, light gates with timers, or a data logger with an accelerometer. The spec names acceleration of free fall as an example activity, but your school might run a different one that still covers the same techniques.

The OCR Physics A specification states you need to complete a minimum of 12 assessed practicals that between them cover PAG1 through PAG12. The spec also notes that one PAG can be split across more than one activity (centres could, for instance, split PAG3 into two activities), and one activity can tick more than one PAG if the techniques overlap.

Two of the twelve are 'throughout the qualification' PAGs rather than standalone content tags. PAG11 (Investigation) is a free-form investigation slot, and PAG12 (Research skills) runs across the whole course rather than being one lesson. Expect them to show up woven into any PAG where you design your own method or write up a research-style summary.

The table below lists all 12 PAGs in specification order with the apparatus each one typically demands. The example activity in the right-hand column is OCR's suggestion, but your school may run something different that covers the same techniques.

PAG1 builds measurement fluency around moving objects. The classic activity is dropping an object (ball bearing released from an electromagnet onto a trapdoor) to measure g. You time the fall from rest, apply s = ut + ½at² with u = 0, and get g from the gradient of a 2s against t² graph. Expect exam questions on why you plot a straight line rather than quoting one g value, on random versus systematic error, and on the effect of air resistance.

PAG2 is the Young's Modulus practical. A long thin wire fixed at one end, loaded with masses at the other, with extension measured by a travelling microscope or digital vernier gauge. The gradient of a stress-strain graph (not force-extension) gives E. The micrometer and vernier scale skills from this PAG show up everywhere else: resistivity, density, SHM amplitude measurements. Precision here pays off repeatedly.

PAG3 is the resistivity practical. You measure the resistance of a wire of known length and cross-sectional area, then apply ρ = RA / L. The cross-section is where most error creeps in: a 0.2 mm diameter wire measured with a micrometer at three points, averaged, then squared. The spec explicitly notes PAG3 can be split across two activities, which is a hint that your school might run resistivity in one lesson and the I-V characteristic of a filament lamp or diode in another.

PAG4 covers the circuit-building skills. Potential-divider networks, Wheatstone-bridge-style balance circuits, thermistor and LDR applications. The examinable understanding is which component you'd pick for which sensor task, and how a loaded potential divider's output voltage shifts under different conditions.

PAG5 is the big waves practical. Two-source superposition using a double slit for light (laser onto a diffraction grating or Young's double slit) and a signal generator with two loudspeakers for sound. The output is a wavelength from λ = ax/D or d sin θ = nλ, and the techniques (dark room, measuring fringe spacing with a travelling microscope, averaging over several fringes) take real care.

PAG6 is Planck's constant from LEDs. You measure the threshold voltage V where each LED just lights, then use hf = eV with the LED's known wavelength to get h. Plot V against 1/λ: the gradient is hc/e, so h = gradient × e / c. The practical links to Module 4 (quantum physics) and often appears on written papers as a graph-plotting exercise with error-bar interpretation.

PAG7 is the ionising-radiation PAG. Alpha, beta and gamma absorption through paper, aluminium of varying thickness, and lead. Safety is non-negotiable: distance (handling sources with long tongs), time (minimising exposure), and shielding (lead storage). You should be comfortable explaining what the inverse-square law for a gamma source looks like and how background radiation is corrected for.

PAG8 is the gas-law practical. The example OCR flags is estimating absolute zero: measure gas pressure at a series of temperatures (ice bath, room temperature, warm water, hot water), plot pressure against temperature in Celsius, and extrapolate the line back to where pressure would be zero. The intercept gives you an estimate of -273°C.

PAG9 is capacitor discharge. You charge a capacitor through a resistor to a known voltage, then discharge it and record V against t with a data logger. Plot ln V against t: the gradient is -1/RC, so you can extract the time constant and, with a known capacitor or resistor, the unknown component value. Written-paper questions often give you a dataset and ask you to extract RC from the gradient.

PAG10 is simple harmonic motion. Mass-spring systems or simple pendulums are the usual rigs. The output is T from timing many oscillations (not one), then plotting T² against m or L to get k or g from the gradient.

PAG11 is deliberately a free-form investigation slot. The example OCR flags is finding the specific heat capacity of a material, but any extended, self-designed investigation with proper variable control and an error analysis can count. The spec treats it as 'throughout the qualification', so it isn't tied to one lesson.

PAG12 is the research-skills tag that runs across the whole course. Any extended write-up where you find primary-source data, evaluate a published method, or make a reasoned judgement from the literature can tick it. The spec examples (GPS, radioactive tracers in medicine) are prompts for referenced, evaluation-style write-ups rather than bench practicals.

Your teacher assesses you against the Common Practical Assessment Criteria, or CPAC, set out in the OCR Physics A specification. There are five competencies: Following written procedures, Applying investigative approaches, Safely using a range of practical equipment and materials, Making and recording observations, and Researching, referencing and reporting. Your teacher needs to be confident you meet each one consistently and routinely across your 12 (or more) assessed practicals.

CPAC applies identically across all three A-Level sciences and across awarding bodies. Your result is reported on your A-Level certificate as Pass or Not Classified. Your A-Level grade is unaffected either way.

Your lab book is the main evidence trail across your assessed practicals.

Module 1 of the spec (Development of practical skills in physics) is examined across all three papers: Paper 1 Modelling physics (2h 15m, 100 marks), Paper 2 Exploring physics (2h 15m, 100 marks), and Paper 3 Unified physics (1h 30m, 70 marks). Practical content appears on every paper. Our complete guide to OCR A-Level Physics breaks down all three papers and their weighting across the six content modules.

Graph plotting, gradient extraction, log-linearisation (ln V against t, for instance), error-bar interpretation and uncertainty calculations all appear in the practical-skills content. The practical-skills questions tend to reward students who can plot and read graphs quickly: that's where the time pressure bites hardest.

A few recurring myths about OCR Physics practicals. The first is thinking the Practical Endorsement feeds into the A*-E grade. It doesn't: the grade is set entirely by the three written papers. The endorsement is reported separately on your certificate, as Pass or Not Classified.

The second is terminology drift. 'Required practicals' is an AQA term; OCR uses 'PAG' (Practical Activity Group). If you see an AQA-style required-practical list for Physics, it's not applicable to OCR, and the lists themselves are different.

The third is confusing OCR Physics A (H556) with OCR Physics B Advancing Physics (H557). The two share a lot of underlying content but have different practical structures. This guide is strictly H556.

The fourth, specific to PAG7, is thinking you need a formal radiation licence to do the practical. You don't: your school handles the sources under its own radiation safety arrangements, and your teacher runs the handling. What you need to know for the written paper is the shielding, distance, and time principles, not the licensing framework.

The students who pick up practical-skills marks on the written papers work backwards from past-paper questions. Our wider A-Level revision techniques guide covers the general approach, but a few physics-specific habits make a difference.

For each PAG, build a one-page summary: apparatus, technique, output quantity, main source of error, and two realistic improvements. Then write it from memory and check it. Improvements questions trip students up most under exam time pressure.

Practise log-linearisation. Capacitor discharge (ln V against t), radioactive decay (ln N against t), SHM period scaling (T² against m or L), Planck's constant (V against 1/λ). Take logs of both sides, identify what the gradient represents, extract the physical quantity. Three or four worked examples cover almost every graph question on Paper 2 and Paper 3.

Master uncertainties. Absolute, fractional and percentage; how they combine when quantities are added, multiplied, or raised to a power. These come up on short-answer practical-skills questions worth two or three marks each.

Finally, drill the apparatus diagrams. A labelled potential-divider circuit, a Young's double-slit setup, a capacitor discharge circuit with data-logging voltmeter. Clean diagrams with every component named and the measuring instrument in the correct place pick up easy marks.

Cognito covers every practical-skills topic in Module 1 with short video lessons on each PAG technique and exam-style questions pulled from past papers. If you also want to pin down the exam-paper reference material, our OCR A-Level Physics equation sheet guide walks through every formula provided in the booklet you're handed in the exam.