OCR A Level Physics A: Practical Endorsement skills, apparatus and techniques (H556)

This guide covers OCR A Level Physics A (H556), Module 1, section 1.2 “Practical skills assessed in the practical endorsement”: 1.2.1(a)-(j) practical skills and 1.2.2(a)-(l) use of apparatus and techniques. It follows the OCR specification, Version 3.0 (March 2026), and uses its numbering. Section 1.1 (planning, analysis and evaluation, assessed in the written papers) is covered in Development of practical skills. Course hub: OCR A Level Physics. Printable checklist. Condensed recall: revision notes. Questions: practice set. Not sure where to start? Try the free 10-minute diagnostics.

What the Practical Endorsement is

The Practical Endorsement (Component 04) is teacher assessed and reported separately. It does not contribute to the overall A level grade. You work towards a Pass by completing a minimum of 12 practical activities that cover the Practical Activity Groups (PAG1 to PAG12), and by consistently and routinely showing the Common Practical Assessment Criteria (CPAC). You may work in groups, but your own competence must be clear.

The CPAC list five competencies:

1. Follows written procedures.
2. Applies investigative approaches and methods when using instruments and equipment (including controlling variables and choosing equipment that gives suitably accurate results).
3. Safely uses a range of practical equipment and materials.
4. Makes and records observations.
5. Researches, references and reports.

The skills and instruments in section 1.2 are how you show these. Written-paper questions may draw on the practical activities, so learn each technique below as an exam topic too.

1.2.1 Practical skills

Outcome	What you need to do
(a)	Use investigative approaches, including solving problems in a practical context
(b)	Use equipment and materials safely and correctly; identify hazards and minimise risk
(c)	Follow written instructions
(d)	Make and record observations and measurements
(e)	Keep appropriate records of experimental activities
(f)	Present information and data in a scientific way
(g)	Use software and tools to process data, research and report
(h)	Use online and offline research (websites, textbooks, printed sources)
(i)	Cite sources correctly
(j)	Use a wide range of instruments, equipment and techniques

Investigating, instructions and safety (a), (b), (c)

An investigative approach means you decide what to vary, what to measure and what to hold constant. Identify the independent variable, the dependent variable and the controls, and say how you will control any variable you cannot hold fixed (for example room temperature drifting). Choose instruments whose resolution suits the size of the quantity: a ruler is fine for a 1.5 m wire length but not for a 0.35 mm diameter.

For safety, work in three steps: name the hazard, say who or what could be harmed and how, then state the control. Make the control specific to the apparatus.

Apparatus	Hazard	Control
Laser	Eye damage from the beam or a reflection	Use the lowest suitable power, never look along the beam, remove shiny objects, stop the beam beyond the screen
Mains-powered or high-current circuit	Heating of wires and components, shock	Keep current low, switch off to change the circuit, check for hot wires
Hot water, heaters	Burns	Clamp apparatus, keep leads clear, allow cooling
Falling masses, stretched wires	Impact, whiplash	Safety goggles, sand tray or box under the load, keep feet clear
Radioactive source	Ionising radiation	Covered below

Recording and presenting (d), (e), (f)

Record data at the time, in a table, with the quantity and unit in each column heading (for example “t / s”). Give all values in a column to the same number of decimal places, matching the resolution of the instrument. Keep a dated record of what you did, including repeats and anomalies. Graphs need labelled axes with units, a sensible scale that uses most of the grid, points plotted accurately, and a best-fit line or curve.

Software, research and citing (g), (h), (i)

Use a spreadsheet or graph package to calculate and plot, and to find a gradient or line of best fit. Check software output against a hand estimate. For research (PAG12), use more than one source, prefer textbooks, university or professional-body pages and official data, and note when information is out of date or comes from an unsourced page. To cite, record the author or organisation, year, title, publisher or web address and the date you accessed it. Put the citation next to the information it supports. The OCR Practical Skills Handbook gives the approved guidance on citing.

1.2.2 Apparatus and techniques

(a) Analogue instruments and interpolation

Analogue apparatus covers rulers, thermometers, protractors, pressure gauges, newton meters and measuring cylinders. Interpolating means estimating a reading between two marks, usually to the nearest half or fifth of a division. Read at eye level to avoid parallax, and read a liquid at the bottom of the meniscus.

(b) Digital instruments and multimeters

A multimeter measures current (in series), voltage (in parallel) and resistance (component isolated, no power). Check the range, the leads in the correct sockets and the zero. The resolution is the last digit, but the reading may be less accurate than that. Top-pan balances measure mass; digital stopwatches measure time.

(c) Increasing accuracy of a measurement

Timing multiple oscillations spreads one reaction-time error over many periods. A fiducial marker, a fixed pointer at the equilibrium position, gives a clear point at which to start and stop timing. A set square checks that a rule or object is perpendicular to the bench; a plumb line shows the true vertical.

Worked example. A pendulum completes 20 oscillations in 36.8 s. The uncertainty in starting and stopping the stopwatch is ±0.2 s.

T = 36.8 / 20 = 1.84 s
Uncertainty in T = 0.2 / 20 = 0.01 s, which is 0.01 / 1.84 = 0.54 %

Timing one oscillation would give 0.2 / 1.84 = 11 %, twenty times larger.

(d) Stopwatch and light gates

A stopwatch is limited by your reaction time. A light gate and datalogger records the time a card blocks the beam with no reaction-time error, so it suits short or fast events. Measure the card width with a vernier or micrometer.

Worked example. A 0.050 m card passes gate 1 in 0.040 s and gate 2 in 0.025 s. The time between the gates is 0.35 s.

v₁ = 0.050 / 0.040 = 1.25 m/s   v₂ = 0.050 / 0.025 = 2.0 m/s
a = (v₂ − v₁) / t = (2.0 − 1.25) / 0.35 = 2.1 m/s²

A 0.5 mm uncertainty in the card width is 1.0 % of 0.050 m and affects both speeds.

(e) Vernier and micrometer scales

A micrometer has a main scale (0.5 mm marks on the sleeve) and a thimble scale (0.01 mm per division). Close the jaws first to find the zero error, and use the ratchet so you do not crush the object.

Worked example. The sleeve shows 6.5 mm and the thimble reads 28 divisions. The jaws closed read +0.03 mm.

Reading = 6.5 + 0.28 = 6.78 mm
Corrected = 6.78 − 0.03 = 6.75 mm

A vernier caliper has a vernier scale next to the main scale. If the main scale shows 14 mm and the 17th vernier mark lines up (resolution 0.02 mm), the reading is 14 + 17 × 0.02 = 14.34 mm. Take diameters at several positions and in different directions, then average, because wires are rarely uniform.

(f), (g) Circuits

Build from a circuit diagram by laying out the main series loop first, then adding voltmeters in parallel. Where polarity matters (cells, LEDs, electrolytic capacitors, ammeters and voltmeters with polarity markings, diodes), check orientation before switching on.

To design a circuit, choose components from the required quantities and check the result.

Worked example. An LED needs 2.0 V and 15 mA from a 6.0 V supply. What series resistor?

R = (6.0 − 2.0) / 0.015 = 267 Ω

The nearest standard value, 270 Ω, gives I = 4.0 / 270 = 14.8 mA. The resistor’s power is 0.0148² × 270 = 0.059 W, so a small quarter-watt resistor is safe.

Check a circuit by measuring: a voltmeter across the LED should read about 2.0 V, and the total of the p.d. values around the loop should equal the supply p.d.

(h) Signal generator and oscilloscope

The signal generator supplies an alternating p.d. of chosen frequency and amplitude. On the oscilloscope, the Y-gain (volts/division) scales the vertical axis and the time-base (time/division) scales the horizontal axis.

Worked example. At 0.5 V/div a trace is 5.2 divisions peak to peak. At 0.2 ms/div one cycle spans 5.0 divisions.

Peak-to-peak p.d. = 5.2 × 0.5 = 2.6 V, so the peak p.d. = 1.3 V
T = 5.0 × 0.2 ms = 1.0 ms, f = 1 / T = 1000 Hz

Set the time-base so that two to five cycles fill the screen, and the Y-gain so the trace fills most of the height.

(i) Generating and measuring waves

Pick one method per investigation:

• Loudspeaker and microphone with a signal generator and oscilloscope: sound wavelength, frequency and speed.
• Ripple tank: a motor-driven dipper makes water waves; a stroboscope, or a lamp above the tank with a screen below, makes the pattern appear stationary so wavelength can be measured over several wavelengths.
• Vibration transducer: stationary waves on a string or spring.
• Microwave or radio source with a receiver: wavelength from the spacing of stationary-wave minima. Measure across many minima.

(j) Laser or light source

A laser with a double slit or diffraction grating shows interference and diffraction. For a double slit, λ = a w / D, where a is the slit separation, w the fringe separation and D the slit-to-screen distance.

Worked example. a = 0.40 mm and D = 1.80 m. Eight fringe spacings span 20.0 mm.

w = 20.0 / 8 = 2.50 mm
λ = (0.40 × 10⁻³ × 2.50 × 10⁻³) / 1.80 = 5.6 × 10⁻⁷ m = 556 nm

A ±1 mm uncertainty is 40 % of one spacing but 5 % of the 20.0 mm span, so measuring across many fringes is better.

(k) ICT

Computer modelling tests a theory against data. A data logger with sensors (motion, light, temperature, voltage, current) samples at a chosen rate. Choose the sampling rate so a signal is sampled many times per cycle, and a long enough run to capture the whole event. Software processes the data (graphs, gradients, line of best fit).

(l) Ionising radiation and detectors

A Geiger-Muller tube with a counter or ratemeter detects ionising radiation. Always measure the background count rate with the source absent and subtract it.

Worked example. Background: 72 counts in 300 s. Source: 1944 counts in 60 s.

Background = 72 / 300 = 0.24 s⁻¹
Source = 1944 / 60 = 32.4 s⁻¹
Corrected rate = 32.4 − 0.24 = 32.2 s⁻¹

Count uncertainty is about √N, so √1944 = 44, which is 2.3 %. A larger count gives a smaller percentage uncertainty.

Safe use: keep sources stored in their container when not in use, handle with tongs, point them away from people, keep the time and exposure short and the distance large, and follow your centre’s rules.

Common errors

• Giving a measurement to more decimal places than the instrument resolves.
• Forgetting to correct for zero error or background count.
• Quoting a hazard without a control that fits the apparatus.
• Timing a single oscillation and calling it “accurate”.
• Writing only “from the internet” as a source.

Where to go next

Use the revision notes to consolidate and the practice set to test yourself. Related pages: practical skills revision notes and practical skills practice.

Official syllabus

OCR, A Level Specification Physics A (H556), Version 3.0 (March 2026), for first assessment in 2017: sections 1.2.1, 1.2.2 and 5g.