Key term
WJEC A-Level Physics 1420QS
Basic Physics
Kinematics
Dynamics
Energy Concepts
Solids Under Stress
Using Radiation to Investigate Stars
Particles and Nuclear Structure
Topic overviewQuarks, leptons and hadronsThe four interactions and conservation lawsThe first generation of quarks and leptonsAntiparticles and annihilationBaryons, antibaryons and mesonsDeducing quark compositions from chargeBeta decay and quark flavour changeTesting a reaction against the conservation rules
Conduction of Electricity
Resistance
Topic overviewCalculating resistance from resistivityPotential difference, Ohm's law and powerResistivity, temperature and superconductivityThe volt: energy transferred per unit chargeCurrent–voltage characteristics of non-ohmic componentsMeasuring resistance and resistivity in the laboratoryThe heating effect of a current and choosing a power equationThermistors and how a semiconductor's resistance falls with temperatureConductance, conductivity and comparing materials
D.C. Circuits
Topic overviewKirchhoff's laws, and resistors in series and parallelPotential dividers, emf and internal resistanceCells, resistivity, power and energyWorking out currents and potential differences in resistor networksSensor circuits with thermistors and LDRsInternal resistance, power transfer and short-circuit currentAmmeters, voltmeters and their effect on the circuit
The Nature of Waves
Wave Properties
Topic overviewEnergy transfer and the wave equationTransverse and longitudinal waves, path difference and intensityDiffraction and superpositionTwo-source interference and the diffraction gratingStationary wavesHow much a wave spreads at a gap or an obstacleCoherence and the conditions for observable interferenceYoung's double slit and λ = ay/DMeasuring wavelength with a diffraction gratingMeasuring the speed of sound with stationary waves
Refraction of Light
Photons
Topic overviewPhoton energy and the electronvoltThe photoelectric effectStopping potential and the Planck constantThe photoelectric effect and photon energiesLine spectra and energy levelsDemonstrating the photoelectric effectThe electromagnetic spectrum and typical photon energiesElectron diffraction and the de Broglie relationshipRadiation pressure
Lasers
Circular Motion
Vibrations
Topic overviewSimple harmonic motion and its equationsOscillating systems and energyDamping and resonanceThe simple pendulumThe mass–spring oscillatorThe displacement and velocity equationsGraphs of displacement, velocity and accelerationThe energy interchange in simple harmonic motionFree and forced oscillationsLight, heavy and critical damping
Kinetic Theory
Thermal Physics
Topic overviewInternal energy and heatWork, the first law and specific heat capacityThermal equilibrium, temperature and absolute zeroThe internal energy of an ideal monatomic gasWork done by a gas at constant pressureThe p–V diagram and work as an areaSign conventions and special cases of the first lawMeasuring specific heat capacity
Nuclear Decay
Nuclear Energy
Capacitance
Topic overviewCapacitance and the parallel plate capacitorEnergy, combinations and RC circuitsCharging at constant current and measuring capacitanceDielectrics and relative permittivityThe uniform field between capacitor platesEnergy stored in a capacitor and the Q–V graphExponential discharge, the time constant and log graphsCapacitors in series and parallel: charge and potential difference sharing
Electrostatic and Gravitational Fields of Force
Topic overviewElectric and gravitational fields comparedField lines, equipotentials and combining fieldsElectric potential and the work done on a chargeGravitational potential and potential energyAdding potentials and fields from several sourcesEquipotential surfacesComparing the two fields point by point
Orbits and the Wider Universe
Topic overviewKepler's laws and orbital motionThe Doppler effect, dark matter and the expanding universeNewton's law of gravitation applied to orbitsDeriving Kepler's third lawFinding the mass of a central objectGalactic rotation curves and dark matterThe centre of mass of a two-body systemRadial velocity and the Doppler shift of spectral linesHubble's law and the age of the universe
Magnetic Fields
Topic overviewMagnetic fields and field patternsMagnetic flux density and the force on a conductorThe force on a moving charge and its circular pathThe Hall effect and the Hall voltageMagnetic fields due to a current in a wire and in a solenoidForces between current-carrying conductorsCharged particle beams, velocity selectors and accelerators
Electromagnetic Induction
Option A: Alternating CurrentsOption A
Option B: Medical PhysicsOption B
Topic overviewMedical physicsUltrasound imagingRadiation and living tissueX-ray production and beam controlAttenuation and half-value thicknessRadiography, fluoroscopy and CT scanningAcoustic impedance and ultrasound reflectionMagnetic resonance imagingAbsorbed dose, equivalent dose and effective doseRadionuclide tracers, the gamma camera and PET
Option C: The Physics of SportsOption C
Topic overviewCentre of gravity, stability and momentsRestitution, moment of inertia and angular momentumRotational energy, projectiles and the flight of a ballMoments in the muscles and jointsApplying the impulse equation in sportMoment of inertia and angular kinematicsTorque, angular momentum and its conservationRotational energy and energy conservation in sport
Option D: Energy and the EnvironmentOption D
Topic overviewFactors affecting the rate at which the temperature of the Earth risesThe Earth's thermal equilibrium, Wien's law and Stefan's lawRenewable and non-renewable sourcesSolar energy and photovoltaic cellsWind, tidal and hydroelectric powerNuclear fission and fusion as energy sourcesU-values and rates of heat lossFuel cells and how they workFuel cells: benefits, limitations and the hydrogen economyThermal conduction, conductivity and insulation
Mathematical Requirements (Appendix C)
Topic overviewSignificant figures and arithmetic meansUncertainty and how uncertainties combineAlgebraic symbols and proportionalityRearranging and solving equationsSmall angle approximationsTangents and instantaneous rates of changeAreas under curves and numerical methodsReading a tangent on a motion graphStraight-line graphs and y = mx + cWhat a gradient and an intercept representLinearising a relationship to find a constantLog plots of exponential decayChoosing what to plot to find a constantLogarithmic scales and orders of magnitudeWorking with base-ten logarithmsThe shapes of common graphsInverse and root relationships on a graphAreas, volumes and PythagorasGeometry applied to physical situationsSubstituting into physical equationsTrigonometry and right-angled trianglesResolving a force into componentsRadians, arc length and force diagramsRandom processes and translating between representationsMean values and periodic functionsSymbols for approximation and comparison
Energy Concepts
- 6 subtopics
- 18 things to know
- AS Unit 1
What Energy Concepts covers
Energy Concepts is examined on AS Unit 1 of WJEC Physics, Motion, Energy and Matter. 85 recall questions across 6 subtopics.
The 6 subtopics
Each one has its own page.
- Work and powerRecall questions on Work and power.Open →
- Conservation of energy and efficiencyRecall questions on Conservation of energy and efficiency.Open →
- The work–energy relationshipRecall questions on The work–energy relationship.Open →
- Gravitational potential energy and energy interchangeRecall questions on Gravitational potential energy and energy interchange.Open →
- Elastic potential energy and the force–extension graphRecall questions on Elastic potential energy and the force–extension graph.Open →
- Power, velocity and the efficiency of machinesRecall questions on Power, velocity and the efficiency of machines.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is power?
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What is the SI unit of work, and what is it equivalent to in base units?
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Define each symbol in the relationship Fx = ½mv² − ½mu², giving its unit.
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Describe the interchange of energy during one complete swing of a pendulum.
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Why does the power needed to drive a car at a steady speed rise so sharply as the speed increases?
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State the principle of conservation of energy.
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Write down the relationship between the work done by the resultant force on a body and the change in the body's kinetic energy.
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Why is only the change in gravitational potential energy ever calculated near the Earth's surface, and never an absolute value?
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Give the expression for the energy stored in a spring obeying Hooke's law in terms of the stretching force and the extension.
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Why is the energy stored in a spring ½Fx rather than Fx?
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State the equation for the power developed by a force acting on a body moving at constant velocity, defining each symbol with its unit.
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Define the work done by a constant force acting along the line of motion.
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State the equation for the gravitational potential energy gained by a mass raised through a height.
Key term
What does it mean for the work done on a body to be negative?
Numbers
Calculate the gravitational potential energy gained by a 65 kg climber ascending 320 m, taking g as 9.81 N kg⁻¹.
Numbers
Calculate the energy stored in a spring of spring constant 240 N m⁻¹ stretched by 8.0 cm.
Key term
Why does the useful output power of a vehicle at a steady speed equal the total resistive force multiplied by that speed?
Take Energy Concepts further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Work vs Power
Work: the product of a force and the distance moved along the line of that force. Power: the rate at which energy is transferred.
Gravitational potential energy vs Elastic potential energy
Gravitational potential energy: the energy stored by raising a mass through a height. Elastic potential energy: the energy stored by stretching or compressing a spring.
Questions from this topic
Each one with the model answer underneath.
- 1
Define the work done by a constant force acting along the line of motion.
Model answer
Work done is the product of the force and the distance moved in the direction of the force.
- 2
State the equation for the work done by a constant force acting along the line of motion.
Model answer
W = Fx, where W is the work done, F is the force and x is the distance moved in the direction of the force.
- 3
What is the SI unit of work, and what is it equivalent to in base units?
Model answer
The joule (J), equivalent to a newton metre, or kg m² s⁻² in base SI units.
- 4
How is the work done calculated when the force is not along the line of motion?
Model answer
W = Fx cos θ, where θ is the angle between the force and the direction of motion.
- 5
Why does the cos θ term appear when a force acts at an angle to the motion?
Model answer
Only the component of the force along the direction of motion does work, and that component is F cos θ.
- 6
How much work is done by a force acting at right angles to the direction of motion, and why?
Model answer
None, because cos 90° = 0, so the force has no component along the direction of motion.
What is inside Levo
Six ways to work the same material.
Energy Concepts revision questions
- What does Energy Concepts cover in WJEC A-Level Physics?
- 6 subtopics: work and power, conservation of energy and efficiency, the work–energy relationship, gravitational potential energy and energy interchange, elastic potential energy and the force–extension graph and power, velocity and the efficiency of machines. Each one has its own page with questions and model answers.
- How is Energy Concepts organised?
- By the WJEC 1420QS specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Energy Concepts, 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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