Numbers
Edexcel A-Level Physics 9PH0
Working as a Physicist
Topic overviewSI base units, derived units and homogeneityUnit prefixes, conversion and order-of-magnitude estimatesResolution, random errors and systematic errorsUncertainty and how uncertainties combineImproving measurements, graphs and evaluating resultsPeer review, publication and scientific integrityRisk, benefit and the role of science in society
Mechanics
Topic overviewThe equations of uniformly accelerated motionDisplacement-time and velocity-time graphsScalars and vectorsResolving vectors and finding resultantsProjectile motionFree-body diagrams and Newton's first and second lawsNewton's third law, mass and weightTerminal velocity and measuring g by free fallLinear momentum and its conservationElastic and inelastic collisions in one dimensionThe moment of a forceCentre of gravity, equilibrium and the principle of momentsWork done by a forceKinetic and gravitational potential energyConservation of energy and dissipationPower, and the equation P = FvEfficiency and wasted energy
Electric Circuits
Topic overviewCurrent, charge and potential differenceResistance, Ohm's law and ohmic behaviourElectrical power and energyKirchhoff's laws: the current and potential difference rulesCombining resistances in series and parallelCircuit calculations, meters and component failureI-V characteristics of conductors, lamps and diodesThermistors, light dependent resistors and resistance changeResistivity and determining it experimentallyCharge carriers, drift velocity and I = nqvAThe potential divider equation and the loading effectSensing circuits with thermistors and light dependent resistorsElectromotive force, internal resistance and lost voltsMeasuring e.m.f. and internal resistance, and cells in combination
Materials
Topic overviewDensity and how it is measuredUpthrust and Archimedes' principleFloating, sinking and upthrust calculationsViscosity, laminar flow and Stokes' lawTerminal velocity of a sphere falling through a liquidMeasuring viscosity by the falling-ball methodHooke's law, stress and strainThe Young modulus and calculations with itDetermining the Young modulus of a wireForce-extension graphs, elastic and plastic deformationStress-strain graphs, ductile and brittle materialsElastic strain energy
Waves and Particle Nature of Light
Topic overviewDescribing a progressive waveThe wave equation and its useLongitudinal and transverse wavesDisplacement-distance and displacement-time graphsMeasuring the speed of sound with an oscilloscopeWavefronts, superposition and phaseCoherence, path difference and phase differenceInterference in practiceStationary waves, nodes and antinodesHarmonics on a stretched stringInvestigating a vibrating string, and air columnsIntensity, the inverse square law and refractive indexRefraction, wave speed and the critical angleTotal internal reflection and measuring refractive indexLenses, ray diagrams and the images they formLens power and the thin lens equationLens calculations and magnificationReflection, transmission and the pulse-echo principlePulse-echo calculations, resolution and ultrasoundPolarisation and diffractionSingle-slit patterns and the diffraction grating equationGrating spectra and measuring wavelengthElectron diffraction and the de Broglie equationde Broglie calculations and wave-particle dualityPhotons and photon energyModels of light and the electronvoltLine spectra and atomic energy levelsThe photoelectric effect and Einstein's equationEvidence for the photon model and photoelectric calculations
Further Mechanics
Topic overviewImpulse and force-time graphsConservation of momentum in two dimensionsInvestigating momentum and analysing collisions on videoElastic and inelastic collisionsKinetic energy, momentum and collision calculationsThe radian, angular displacement and angular velocityAngular velocity, period and frequency of rotationCentripetal accelerationCentripetal force and what provides itVertical loops and centripetal force calculations
Electric and Magnetic Fields
Topic overviewElectric fields and electric field strengthField strength calculations and field diagramsCoulomb's law and the field of a point chargeInverse-square behaviour and combining fieldsElectric potential and field strength as a potential gradientUniform fields between parallel plates, and the potential near a point chargeEquipotentials, field diagrams and work doneCapacitance and the energy stored in a capacitorCapacitor charge and energy calculationsCharging and discharging graphs and the time constantThe exponential decay equations and logarithmic graphsInvestigating capacitor discharge and time-constant calculationsMagnetic flux density, flux and flux linkageForces on currents and moving chargesThe conditions for inducing an e.m.f.Faraday's law and Lenz's lawFlux linkage graphs and induced e.m.f. calculationsAlternating current, peak and r.m.s. valuesOscilloscope traces and alternating current calculations
Nuclear and Particle Physics
Topic overviewNuclide notation, isotopes and the alpha scattering experimentConclusions from alpha scattering and the changing model of the atomThermionic emission and linear acceleratorsThe cyclotron and the radius of a charged particle's pathParticle tracks, conservation laws and why high energies are neededMass-energy equivalence, pair production and annihilationParticle energy units and relativistic lifetimesBaryons, mesons, leptons and quark compositionThe six quarks, antiparticles and fundamental particlesConservation of charge, baryon number and lepton numberQuark changes in beta decay and testing particle equations
Thermodynamics
Topic overviewSpecific heat capacity and specific latent heatMeasuring specific heat capacity and calibrating a thermistorMeasuring specific latent heatInternal energy, temperature and absolute zeroMean kinetic energy and the absolute temperature scaleThe kinetic theory equation and its derivationThe ideal gas equation and molecular kinetic energyBoyle's law and investigating a fixed mass of gasBlack body radiation and Wien's lawThe Stefan-Boltzmann law and stellar calculations
Space
Nuclear Radiation
Topic overviewMass deficit, binding energy and the atomic mass unitBinding energy per nucleon, fission and fusionBackground radiation and the three types of nuclear radiationIonising power, penetration and changes in the nucleusNuclear equations and investigating gamma absorptionActivity, the decay constant and half-lifeDecay graphs and half-life calculations
Gravitational Fields
Oscillations
Topic overviewThe conditions for simple harmonic motionDisplacement, velocity and acceleration in simple harmonic motionThe mass-spring oscillator and the simple pendulumDisplacement, velocity and acceleration graphsReading period, amplitude and speed from oscillation graphsEnergy in an undamped oscillationDamping and where the energy goesFree and forced oscillations and resonanceResonance in practice and determining an unknown mass
Electric Circuits
- 14 subtopics
- 29 things to know
- Papers 1 and 3
What Electric Circuits covers
Paper 1 content, examined again synoptically on Paper 3. Covers current, potential difference and resistance from their definitions, Kirchhoff's two laws and combining resistances, the characteristics of lamps, diodes, thermistors and light dependent resistors, resistivity and drift velocity, potential dividers, and internal resistance.
Where it is assessed
Papers 1 and 3
Advanced Physics I, then the general and practical principles paper.
Check the Pearson Edexcel specification ↗The 14 subtopics
Each one has its own page.
- Current, charge and potential differenceRecall questions on current as rate of flow of charge, the definitions of the coulomb and the volt, and which particles carry the current in a metal.Open →
- Resistance, Ohm's law and ohmic behaviourRecall questions on the definition of resistance and the ohm, the condition attached to Ohm's law, and why R = V/I is not the same statement.Open →
- Electrical power and energyRecall questions on the three power equations and where they come from, which resistor dissipates more in series and in parallel, and why transmission uses high voltage.Open →
- Kirchhoff's laws: the current and potential difference rulesRecall questions on the junction and loop rules, the conservation laws behind them, and how current and potential difference are shared in series and parallel.Open →
- Combining resistances in series and parallelRecall questions on the series and parallel equations, why a parallel combination is smaller than its smallest member, and what adding another branch does.Open →
- Circuit calculations, meters and component failureRecall questions on splitting potential difference and current between resistors, why an ammeter goes in series and a voltmeter in parallel, and what happens when a lamp fails.Open →
- I-V characteristics of conductors, lamps and diodesRecall questions on the shapes of the metallic, filament lamp and diode characteristics, the threshold potential difference, and why a lamp is not ohmic.Open →
- Thermistors, light dependent resistors and resistance changeRecall questions on why a metal's resistance rises with temperature while a thermistor's falls, what NTC means, and why an LDR's resistance drops in bright light.Open →
- Resistivity and determining it experimentallyRecall questions on R = ρl/A, the unit of resistivity, and the wire experiment, including why the diameter is measured repeatedly and the current kept low.Open →
- Charge carriers, drift velocity and I = nqvARecall questions on the meaning of each symbol in I = nqvA, number density and drift velocity, and why a lamp lights instantly although electrons drift slowly.Open →
- The potential divider equation and the loading effectRecall questions on how potential falls along a uniform wire, the divider equation and its derivation, and why the output drops when a load is connected.Open →
- Sensing circuits with thermistors and light dependent resistorsRecall questions on thermistor and LDR dividers, which way round to take the output, choosing the fixed resistor, and switching a heater from a temperature sensor.Open →
- Electromotive force, internal resistance and lost voltsRecall questions on the definition of e.m.f., what internal resistance is, the lost volts, and when terminal potential difference equals e.m.f.Open →
- Measuring e.m.f. and internal resistance, and cells in combinationRecall questions on the experiment, the graph plotted and what its gradient and intercept give, the largest current a cell can deliver, and cells in series and parallel.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
What is meant by potential difference, and how is the volt defined?
Numbers
How are potential difference and resistance defined in terms of energy and charge?
Numbers
What are the equations for electrical power and energy, and why is R = V/I not the same statement as Ohm's law?
Process
Two resistors of different values are connected in series. Which one dissipates more power, and why?
Process
Two resistors of different values are connected in parallel across a supply. Which one dissipates more power, and why?
Process
Why is electrical energy sent long distances at very high potential difference and low current?
Numbers
How is the total resistance of a parallel combination found, and how does the total current relate to the branch currents?
Numbers
How are potential difference and current shared in series and parallel circuits, and why can charge not build up at a junction?
Numbers
How are potential differences shared between series resistors, what happens to a parallel network when a further resistor is added, and what is the combined resistance of two identical resistors R in parallel?
Numbers
What are the current against potential difference characteristics of a metallic conductor and of a diode, and what does the gradient give?
Numbers
Why must the current be kept small when measuring a thermistor's characteristic, and what does the label NTC mean?
Process
Why does a metal's number of conduction electrons stay constant with temperature while a thermistor's and an LDR's resistance fall?
Key term
Why is the characteristic of a filament lamp symmetrical about the origin while that of a diode is not?
Numbers
How does the resistance of a uniform wire depend on its dimensions, and what is the unit of resistivity?
Evaluation
Why should the current be kept low in a resistivity determination, and what is meant by the number density of charge carriers?
Numbers
How do the resistivities of metals and semiconductors compare, and where is the drift velocity greater in a wire that changes thickness?
Numbers
What value of charge should be used for q in I = nqvA when the carriers are electrons?
Numbers
What is the potential divider equation, what advantage does a potentiometer have over a series rheostat, and why does connecting a load across the output reduce the output potential difference?
Numbers
Why does a potential divider waste energy, and how does the output of an LDR divider change with light?
Numbers
How is electromotive force defined, is it really a force, and how does it differ from terminal potential difference?
Numbers
What are the lost volts of a cell, and when does its terminal potential difference equal its electromotive force?
Numbers
Which graph is plotted to find a cell's electromotive force and internal resistance, and what do its gradient and intercept give?
Numbers
What are the e.m.f. and internal resistance of a cell whose terminal p.d. against current graph has intercept 1.55 V and gradient −0.80 V A⁻¹, why should the external resistance never be reduced to almost zero, and what is the largest current a cell can deliver?
Numbers
What would you observe if a cell of high internal resistance were connected to a lamp of very low resistance?
Key term
Which conservation law explains how current divides between the branches of a circuit?
Process
Why does the potential fall uniformly along a uniform current-carrying wire?
Process
What assumptions are needed for the potential to fall at a constant rate along a wire?
Process
How is the potential divider equation derived from the circuit rules?
Take Electric Circuits further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Potential difference vs Electromotive force
Potential difference: electrical energy transferred to other forms per unit charge. Electromotive force: energy transferred from other forms into electrical energy per unit charge.
Resistance vs Resistivity
Resistance: potential difference divided by current. Resistivity: material property linking opposition with conductor geometry.
Series circuit vs Parallel circuit
Series circuit: components share one current path. Parallel circuit: components connect across a common potential difference.
Questions from this topic
Each one with the model answer underneath.
- 1
What is electric current?
Model answer
It is the rate at which charge flows past a point in a circuit, I = ΔQ/Δt.
- 2
State the equation linking current, charge and time:
Model answer
I = ΔQ/Δt, where ΔQ is the charge passing a point in time Δt.
- 3
What is the SI unit of charge, and how is it related to the ampere?
Model answer
The coulomb, where 1 C is the charge that passes when a current of 1 A flows for 1 s.
- 4
Which charged particles carry the current in a metal wire?
Model answer
The free (delocalised) conduction electrons.
- 5
How does the direction of conventional current compare with the direction the electrons actually move in a metal?
Model answer
Conventional current is taken as flowing from positive to negative, which is opposite to the direction the negatively charged electrons drift.
- 6
A current of 0.25 A flows in a wire for 2.0 minutes. How much charge passes a point in the wire?
Model answer
ΔQ = IΔt = 0.25 × 120 = 30 C.
What is inside Levo
Six ways to work the same material.
Electric Circuits revision questions
- What does Electric Circuits cover in Edexcel A-Level Physics?
- 14 subtopics: current, charge and potential difference, resistance, ohm's law and ohmic behaviour, electrical power and energy, kirchhoff's laws: the current and potential difference rules, combining resistances in series and parallel, circuit calculations, meters and component failure, i-v characteristics of conductors, lamps and diodes, thermistors, light dependent resistors and resistance change, resistivity and determining it experimentally, charge carriers, drift velocity and i = nqva, the potential divider equation and the loading effect, sensing circuits with thermistors and light dependent resistors, electromotive force, internal resistance and lost volts and measuring e.m.f. and internal resistance, and cells in combination. Each one has its own page with questions and model answers.
- How is Electric Circuits organised?
- By the Edexcel 9PH0 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Electric Circuits, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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