Edexcel A-Level Physics Revision
Explore Edexcel A-Level Physics revision topics. Check the official specification for complete requirements for your exam year and route.
Qualification code: 9PH0
Course details
Assessment The assessment includes Paper 1, Paper 2 and Paper 3; see the official specification for the full structure.
Tick a point after revising it. Progress is saved on this device and does not measure mastery.
Reviewed course guidance
Revision points, with the explanation beside them
Open a point to read what to know, how to use it in an assessment, a plain-language explanation and a self-check. Answers stay hidden until you choose to reveal them.
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Topic group
Topic 1: Working as a Physicist
- Core
Scope: Core · Topic 1: Working as a Physicist
Open revision guidance
What to know
- Physics models use idealisations; state the assumptions that make an equation or diagram appropriate.
- Use SI units and prefixes, significant figures, graph gradients/areas and uncertainty estimates.
- A conclusion should be supported by measured evidence and acknowledge limitations.
What to do in an assessment
- Translate a situation into a diagram and choose quantities before selecting an equation.
- Compare resolution and repeatability; propose improvements tied to an actual source of error.
In plain language
A model is useful because it simplifies a situation, but its predictions apply only when its assumptions fit. State those assumptions rather than using a formula automatically.
Self-check
Why should a physics answer state an assumption such as negligible air resistance?
Show the answer
It identifies the model conditions under which the calculation and conclusion are valid.
Topic group
Topic 2: Mechanics
- Core
Scope: Core · Topic 2: Mechanics
Open revision guidance
What to know
- Constant-acceleration equations connect displacement, velocity, acceleration and time.
- Newton’s laws relate resultant force and acceleration; momentum p = mv is conserved for an isolated system.
- Work done and energy changes provide an alternative way to analyse motion.
What to do in an assessment
- Resolve vectors and choose sign conventions before substituting.
- In collisions compare total momentum before and after and state whether external impulses are negligible.
In plain language
A falling body accelerates under gravity. If you know how velocity changes with time, kinematics predicts its displacement; an energy method can solve the same motion from a change in height.
Self-check
A 1.5 kg object accelerates at 4 m/s². What is the resultant force?
Show the answer
F = ma = 1.5 × 4 = 6 N.
- Core
Scope: Core · Core Practical 1: Determine acceleration of a freely-falling object
Open revision guidance
What to know
- The practical measures fall time over a known distance to determine g.
- For release from rest, s = ½gt²; a graph of distance against time squared has gradient g/2.
- Air resistance, trigger delay and distance measurement create uncertainty.
What to do in an assessment
- Use an electromagnet or reliable release and electronic timing where available; repeat at several distances.
- Plot and fit a straight line, calculate g from the gradient and compare with the accepted value.
In plain language
The object gains speed as it falls. Measuring several distances and times tests whether distance is proportional to time squared and gives gravitational acceleration.
Self-check
If the s versus t² gradient is 4.9 m/s², what is g?
Show the answer
g is twice the gradient: 9.8 m/s².
Topic group
Topic 3: Electric Circuits
- Core
Scope: Core · Topic 3: Electric Circuits
Open revision guidance
What to know
- Use current, potential difference, resistance and charge equations with consistent units.
- Resistivity depends on material and temperature; circuit components can be in series or parallel.
- An emf source with internal resistance has terminal p.d. that changes with current.
What to do in an assessment
- Draw meter connections, simplify the circuit and use Kirchhoff’s laws where required.
- Plot terminal p.d. against current to obtain emf and internal resistance.
In plain language
A battery loses some energy internally when it supplies current. The terminal voltage is therefore lower than the emf while the circuit is loaded.
Self-check
A cell has emf 1.5 V and internal resistance 0.2 Ω at 2 A. Find terminal p.d.
Show the answer
V = ε − Ir = 1.5 − (2×0.2) = 1.1 V.
- Core
Scope: Core · Core Practical 2: Determine electrical resistivity
Open revision guidance
What to know
- Use a wire’s resistance, length and cross-sectional area in ρ = RA/L.
- Obtain resistance from V/I and area from the measured diameter.
- Wire heating can change resistance, so limit current and take readings promptly.
What to do in an assessment
- Measure diameter at several locations, find mean area and measure wire length accurately.
- Plot R against L when appropriate; calculate resistivity with consistent SI units.
In plain language
Resistance rises with length, while a thicker wire offers more paths for charge. Resistivity isolates the material property from wire dimensions.
Self-check
If resistance doubles when wire length doubles at fixed area, what does that suggest?
Show the answer
It supports R being proportional to length for that material and cross-sectional area.
- Core
Scope: Core · Core Practical 3: Determine emf and internal resistance
Open revision guidance
What to know
- Measure terminal p.d. for several currents; V = ε − Ir.
- The intercept of V against I gives emf and the gradient is −r.
- A variable load changes current; avoid a direct short circuit.
What to do in an assessment
- Collect paired current/voltage readings, repeat and plot a best-fit line.
- Explain why terminal voltage falls as current increases.
In plain language
The current produces a voltage drop inside the cell. The graph separates the open-circuit emf from the internal resistance effect.
Self-check
What does the magnitude of the V-I graph gradient represent?
Show the answer
The internal resistance r.
- Core
Scope: Core · Core Practical 11: Capacitor charge/discharge
Open revision guidance
What to know
- A capacitor’s p.d. changes exponentially through a resistor with time constant τ = RC.
- After one time constant of discharge, voltage is about 37% of its initial value; during charging it reaches about 63% of its final value.
- A data logger or oscilloscope can record voltage versus time.
What to do in an assessment
- Keep resistor and capacitor values known, plot voltage against time and use a log plot or exponential fit.
- Estimate the time constant and identify the initial/final voltage correctly.
In plain language
A capacitor charges quickly at first and then more slowly. The product RC determines the characteristic time scale of this change.
Self-check
What fraction of final voltage is reached after one time constant during charging?
Show the answer
About 63%.
- Core
Scope: Core · Core Practical 12: Thermistor potential divider
Open revision guidance
What to know
- A thermistor’s resistance varies with temperature; a potential divider converts this into an output voltage.
- An NTC thermistor’s resistance decreases as temperature rises.
- Calibration pairs output voltage with measured temperature so a switching threshold can be selected.
What to do in an assessment
- Measure temperature with a calibrated thermometer while recording divider output at stable intervals.
- Plot voltage against temperature and identify a suitable threshold; avoid self-heating and improve thermal contact.
In plain language
A thermistor changes resistance as it warms. In a potential divider this shifts the output voltage, which can trigger a control circuit.
Self-check
What happens to an NTC thermistor’s resistance as temperature rises?
Show the answer
It decreases.
Topic group
Topic 4: Materials
- Core
Scope: Core · Topic 4: Materials
Open revision guidance
What to know
- Stress = force/area; strain = extension/original length; Young modulus = stress/strain in the elastic region.
- Material deformation can be elastic or plastic; the force-extension graph identifies linear and non-linear behaviour.
- Viscosity measures resistance to flow; terminal velocity allows drag and weight forces to balance.
What to do in an assessment
- Measure wire diameter at multiple locations, calculate cross-sectional area and use the linear graph gradient.
- For falling spheres, identify terminal speed from constant-velocity data and account for viscous drag.
In plain language
Young modulus compares how much stress produces a given strain, so materials can be compared independent of their dimensions.
Self-check
What is strain when a 1.0 m wire extends by 2.0 mm?
Show the answer
Strain = 0.002/1.0 = 0.002 (no unit).
- Core
Scope: Core · Core Practical 4: Falling-ball viscosity
Open revision guidance
What to know
- A falling sphere reaches terminal velocity when viscous drag balances its effective weight.
- Terminal speed is found from distance/time over a region where speed is constant.
- Sphere radius, densities and temperature influence the viscosity result.
What to do in an assessment
- Release the sphere centrally, time between marked levels after terminal speed is reached and repeat.
- Control liquid temperature and avoid wall effects; explain measurement uncertainty.
In plain language
At first a sphere speeds up in a liquid. As drag increases it eventually reaches a steady speed, which can be used to infer how strongly the liquid resists flow.
Self-check
What force balance holds at terminal velocity?
Show the answer
Weight is balanced by upthrust and viscous drag, so resultant force is zero.
- Core
Scope: Core · Core Practical 5: Determine Young modulus
Open revision guidance
What to know
- Young modulus = stress/strain using force, cross-sectional area, extension and original length.
- A micrometer measurement of wire diameter determines area; small diameter uncertainty is magnified when squared.
- The material must remain within its elastic limit.
What to do in an assessment
- Measure diameter at multiple points and use a long test length to improve fractional extension accuracy.
- Plot force against extension, identify linear response and calculate the modulus with correct geometry.
In plain language
Young modulus compares the stress needed for a given strain. Thin-wire diameter must be measured carefully because its area strongly affects the calculated stress.
Self-check
Why use a long wire to measure extension accurately?
Show the answer
A given extension is a larger measurable change, reducing the percentage uncertainty relative to its original length.
Topic group
Topic 5: Waves and Particle Nature of Light
- Core
Scope: Core · Topic 5: Waves and Particle Nature of Light
Open revision guidance
What to know
- Wave speed v = fλ; interference and diffraction reveal wave behaviour.
- Photon energy E = hf; photoelectric evidence shows energy arrives in discrete quanta.
- For the photoelectric effect, frequency determines photon energy and intensity determines photon flux.
What to do in an assessment
- Use path difference for interference and threshold frequency for electron emission.
- Explain where a wave model or photon model is being used, rather than treating them as mutually exclusive in every context.
In plain language
Light creates interference patterns like a wave, yet transfers energy in photon-sized packets. The photoelectric threshold depends on each photon’s frequency.
Self-check
Why can intense low-frequency light fail to eject electrons?
Show the answer
If each photon’s energy hf is below the work function, no single photon can release an electron, however many arrive.
Topic group
Topic 6: Further Mechanics
- Core
Scope: Core · Topic 6: Further Mechanics
Open revision guidance
What to know
- Centripetal acceleration is directed toward the centre and requires resultant centripetal force.
- Angular speed and period describe rotation; moment of inertia depends on mass distribution.
- Impulse equals change in momentum; force is the rate of momentum change.
What to do in an assessment
- Separate radial and tangential directions and use the correct radius.
- Use force-time area for impulse and account for direction in momentum.
In plain language
An object moving in a circle accelerates even at constant speed because its direction changes. The inward force continuously bends the velocity vector.
Self-check
What direction is centripetal acceleration?
Show the answer
Toward the centre of the circular path.
- Core
Scope: Core · Core Practical 9: Force and momentum change
Open revision guidance
What to know
- Impulse equals force multiplied by time and equals change in momentum.
- A force sensor and motion data can compare force-time area with momentum change.
- Sensor calibration, sampling rate and collision alignment affect data quality.
What to do in an assessment
- Record force during a collision and measure initial/final velocities; compare integrated force with mΔv.
- Repeat trials and explain why the force-time graph may be noisy.
In plain language
The area under a force-time graph is impulse. It should match the object’s momentum change if the measured force accounts for the interaction.
Self-check
What quantity is given by the area under a force-time graph?
Show the answer
Impulse, equal to change in momentum.
- Core
Scope: Core · Core Practical 10: ICT analysis of collisions
Open revision guidance
What to know
- Video or ICT can track small spheres before and after a collision to estimate velocities.
- Momentum and kinetic energy comparisons classify collision behaviour.
- Scale calibration, frame rate and tracking error affect velocity estimates.
What to do in an assessment
- Calibrate distance in the image, track positions across multiple frames and calculate velocity from gradient.
- Compare total momentum before and after, then interpret any kinetic-energy change.
In plain language
Tracking positions frame by frame gives velocities from the slope of a position-time graph. Those velocities test momentum conservation in a collision.
Self-check
Which graph gradient gives velocity from video tracking?
Show the answer
The gradient of position against time.
Topic group
Topic 7: Electric and Magnetic Fields
- Core
Scope: Core · Topic 7: Electric and Magnetic Fields
Open revision guidance
What to know
- Field strength is force per unit test mass or charge; potential describes energy per unit mass or charge.
- Magnetic force acts on moving charges and current-carrying conductors.
- Changing magnetic flux linkage induces emf; Lenz’s law gives the opposing direction.
What to do in an assessment
- Use field-line diagrams and define the sign/direction convention.
- Apply flux and Faraday’s law with the correct angle and time interval.
In plain language
A changing magnetic flux induces a voltage because the circuit’s magnetic environment changes. The induced effect opposes that change.
Self-check
What does Lenz’s law tell you about the induced current?
Show the answer
It flows in a direction that opposes the change in magnetic flux that produced it.
Topic group
Topic 8: Nuclear and Particle Physics
- Core
Scope: Core · Topic 8: Nuclear and Particle Physics
Open revision guidance
What to know
- Nuclear reactions may release energy through a change in binding energy.
- Particle interactions obey conservation rules for quantities such as charge, baryon number and lepton number.
- Fission splits a heavy nucleus; fusion combines light nuclei.
What to do in an assessment
- Balance conservation quantities before deciding whether a reaction is allowed.
- Use mass defect and E = mc² where required and retain suitable units.
In plain language
A reaction can change particle identities while preserving conserved totals. Checking charge and particle numbers often reveals whether a proposed interaction is possible.
Self-check
What happens to a heavy nucleus during fission?
Show the answer
It splits into smaller nuclei and may release neutrons and energy.
Topic group
Topic 9: Thermodynamics
- Core
Scope: Core · Topic 9: Thermodynamics
Open revision guidance
What to know
- Internal energy is the microscopic kinetic and potential energy of a system.
- The first law tracks energy supplied as heating and work done by or on the system.
- For an ideal gas pV = nRT, with absolute temperature in kelvin.
What to do in an assessment
- State sign conventions before applying a thermodynamic equation.
- Use a p–V graph’s area to determine work where required.
In plain language
Thermodynamics is energy bookkeeping for a system. Heating and work can change its internal energy, and a p–V graph shows work during volume change.
Self-check
Why use kelvin in the ideal gas equation?
Show the answer
It is the absolute temperature scale required for proportional gas relationships.
- Core
Scope: Core · Core Practical 13: Specific latent heat
Open revision guidance
What to know
- Specific latent heat L = E/m for a state change without temperature change.
- Electrical energy input can be estimated from power and time, but energy losses affect the result.
- Mass changed state is found from before/after mass readings.
What to do in an assessment
- Insulate the sample, measure mass and heating time/power and identify when a phase change occurs.
- Discuss heat loss and use a suitable correction or improved insulation.
In plain language
During melting or boiling, energy changes particle arrangement rather than raising temperature. Dividing transferred energy by mass gives specific latent heat.
Self-check
How much energy is needed to vaporise 0.02 kg at L = 2.0×10⁶ J/kg?
Show the answer
E = mL = 0.02 × 2.0×10⁶ = 40 000 J.
- Core
Scope: Core · Core Practical 14: Pressure-volume relation
Open revision guidance
What to know
- For a fixed amount of gas at constant temperature, pV is constant.
- A pressure sensor and adjustable volume can test the Boyle relationship.
- Temperature must be allowed to return to equilibrium after compression.
What to do in an assessment
- Record matched pressure and volume values over a range, repeat and plot p against 1/V.
- Identify leakage, friction and temperature drift as possible limitations.
In plain language
Compressing gas raises pressure, but squeezing warms it temporarily. Waiting for thermal equilibrium keeps the test close to constant temperature.
Self-check
What graph should be linear if p is inversely proportional to V?
Show the answer
Pressure p plotted against 1/V.
Topic group
Topic 10: Space
- Core
Scope: Core · Topic 10: Space
Open revision guidance
What to know
- Luminosity is total power emitted by a star; apparent brightness depends on distance.
- Spectra identify elements and red-shift can indicate recession.
- Stellar evolution depends on mass and proceeds through nuclear-fusion stages.
What to do in an assessment
- Read a Hertzsprung–Russell diagram and connect spectral class/temperature with evolutionary stage.
- Use distance and brightness data only with the correct inverse-square relation.
In plain language
A distant star can appear dim even if it is intrinsically powerful. Separating luminosity from apparent brightness prevents confusing distance with stellar output.
Self-check
Does apparent brightness alone reveal a star’s luminosity?
Show the answer
No; distance must also be known because apparent brightness decreases with distance.
Topic group
Topic 11: Nuclear Radiation
- Core
Scope: Core · Topic 11: Nuclear Radiation
Open revision guidance
What to know
- Radioactive decay is random for an individual nucleus; activity and half-life describe large samples.
- Radiation types differ in ionising ability and penetration; exposure dose depends on source and pathway.
- Inverse-square behaviour applies to point-source intensity in suitable geometry.
What to do in an assessment
- Subtract background count and use half-life or exponential models as requested.
- Distinguish contamination from irradiation and justify protective measures.
In plain language
A detector’s count includes background. Correcting for it allows the activity due to the test source to be estimated.
Self-check
What should be done to a measured count rate before estimating source count rate?
Show the answer
Subtract the background count rate measured over the same time.
- Core
Scope: Core · Core Practical 15: Gamma absorption by lead
Open revision guidance
What to know
- Measure gamma count rate as absorber thickness changes; the count decreases through attenuation.
- Subtract background radiation and keep source-detector geometry and counting duration fixed.
- Radiation intensity is reduced rather than necessarily reduced to zero by lead.
What to do in an assessment
- Add known lead thicknesses, repeat long counts and plot corrected count rate against thickness.
- Use shielding tongs and distance/time precautions; state limitations from random counts.
In plain language
Each additional layer of lead absorbs some photons. Counts fluctuate randomly, so longer counting times and background correction improve the comparison.
Self-check
Why subtract background count from each measured total?
Show the answer
To isolate counts attributable to the gamma source from ambient radiation.
Topic group
Topic 12: Gravitational Fields
- Core
Scope: Core · Topic 12: Gravitational Fields
Open revision guidance
What to know
- Newton’s law of gravitation follows an inverse-square relation with separation.
- Gravitational field strength is force per unit mass; potential is work per unit mass.
- For circular orbits, gravitational force supplies centripetal force and orbital energy changes with radius.
What to do in an assessment
- Measure radius from the centre of the attracting body.
- Keep gravitational potential negative under the zero-at-infinity convention.
In plain language
A satellite’s orbit depends on the balance between its tangential speed and gravity’s inward pull. A smaller orbit requires different speed and energy.
Self-check
From what point should satellite orbital radius be measured?
Show the answer
From the centre of the body being orbited.
Topic group
Topic 13: Oscillations
- Core
Scope: Core · Topic 13: Oscillations
Open revision guidance
What to know
- Simple harmonic motion has acceleration proportional to displacement and directed toward equilibrium.
- An oscillator exchanges kinetic and potential energy; damping transfers energy out of the oscillation.
- Resonance occurs when driving frequency matches natural frequency, producing a large response.
What to do in an assessment
- Use phase and amplitude information from displacement-time graphs.
- Explain why damping reduces amplitude and why resonance can be useful or hazardous.
In plain language
At resonance a repeated push arrives at the right phase to add energy each cycle, so oscillation amplitude can grow until damping balances input.
Self-check
What happens to oscillation amplitude near resonance?
Show the answer
It can become large because energy is added efficiently at the natural frequency.
- Core
Scope: Core · Core Practical 16: Unknown mass from resonant frequencies
Open revision guidance
What to know
- Resonant frequency of a mass-spring system depends on mass and spring stiffness.
- Measure resonant frequency for known masses, then use the relationship to infer an unknown mass.
- Damping, spring mass and identifying the peak frequency affect uncertainty.
What to do in an assessment
- Collect frequencies over several known masses and plot an appropriate linearised relation.
- Use the graph to estimate unknown mass and discuss whether the spring’s own mass matters.
In plain language
Adding mass changes the system’s natural oscillation frequency. A calibration graph maps frequency to mass so an unknown can be estimated.
Self-check
What should be used to infer an unknown mass from calibration data?
Show the answer
The measured resonant frequency and the relationship/graph established with known masses.
Topic group
Topic 5: Waves
- Core
Scope: Core · Core Practical 6: Speed of sound using oscilloscope
Open revision guidance
What to know
- A signal generator drives a speaker; a microphone converts sound to an electrical signal displayed on an oscilloscope.
- Measure wavelength or time delay and use v = fλ or the relevant distance/time relation.
- Oscilloscope time-base and signal frequency must be calibrated/read consistently.
What to do in an assessment
- Move the microphone by known distances and count phase cycles, or use a two-channel time delay.
- Repeat readings and explain how microphone position and reflection affect uncertainty.
In plain language
The oscilloscope displays the sound signal as a voltage trace. Comparing the transmitted and received signals reveals how long the sound takes to travel.
Self-check
If frequency is 500 Hz and wavelength 0.68 m, find sound speed.
Show the answer
v = fλ = 500 × 0.68 = 340 m/s.
- Core
Scope: Core · Core Practical 7: Vibrating string
Open revision guidance
What to know
- Vary length, tension and mass per unit length to test their effect on stationary-wave frequency.
- Adjacent nodes are separated by half a wavelength.
- Keep other variables controlled for each relationship.
What to do in an assessment
- Use a signal generator to find resonant frequencies and measure node spacing.
- Repeat at different string lengths/tensions and discuss identifying resonance.
In plain language
A stationary wave forms when the reflected wave interferes with the incoming wave. Only particular frequencies fit between the fixed ends.
Self-check
If adjacent nodes are 0.25 m apart, what is wavelength?
Show the answer
λ = 2 × 0.25 = 0.50 m.
- Core
Scope: Core · Core Practical 8: Diffraction grating wavelength
Open revision guidance
What to know
- A diffraction grating produces bright maxima at angles determined by nλ = d sinθ.
- d is grating spacing and n is diffraction order.
- A longer screen distance can improve measurement precision but needs accurate alignment.
What to do in an assessment
- Measure distance from central maximum to each order and screen distance to calculate angle.
- Use several orders/symmetric maxima and discuss line-width uncertainty.
In plain language
The grating’s many slits make light waves interfere. Bright bands occur only at angles where path difference is a whole wavelength.
Self-check
What path difference gives a bright maximum in a diffraction grating?
Show the answer
An integer multiple of wavelength, nλ.
Earlier topic checklist
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