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 and Magnetic Fields
Capacitance and the energy stored in a capacitor
- 2 things to know
- Papers 1 and 3
Overview
Recall questions on the definition of capacitance and the farad, why Q/V is constant, and the three expressions for the energy stored.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
Why is the ratio Q/V constant for a capacitor, what happens to the charge if the potential difference falls to a third, and what do the gradients of V-Q and Q-V graphs give?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How is capacitance defined?
Model answer
It is the charge stored per unit potential difference across the capacitor, C = Q/V.
- 2
What is the unit of capacitance and how is it defined?
Model answer
The farad, F, where one farad is one coulomb of charge stored per volt of potential difference.
- 3
Why are practical capacitors usually rated in microfarads or smaller?
Model answer
Because the farad is a very large unit, so everyday capacitors have values of the order of μF, nF or pF.
- 4
What is meant by the charge stored on a capacitor, given that its two plates carry opposite charge?
Model answer
It means the magnitude of the charge on one plate, since the plates carry equal and opposite amounts.
- 5
Why is the ratio Q/V constant for a given capacitor?
Model answer
Because the charge stored is directly proportional to the potential difference across it, so their ratio is fixed by the capacitor's construction.
- 6
What shape is a graph of potential difference against charge stored for a capacitor?
Model answer
It is a straight line through the origin, with a gradient equal to 1/C.
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