Key term
Edexcel GCSE Combined Science Physics 1SC0
Key Concepts of Physics
Motion and Forces
Topic overviewScalar and vector quantitiesExamples of vectors and scalars, and velocitySpeed, distance, time and distance-time graphsAcceleration and the equation v squared minus u squaredVelocity-time graphs and free fallMeasuring speed in the laboratory, and typical everyday speedsNewton's first law, and investigating force, mass and accelerationNewton's second and third lawsWeight, mass and gravitational field strengthReaction time, stopping distance and large decelerationsFactors affecting stopping distance and reaction time
Conservation of Energy
Waves
Light and the Electromagnetic Spectrum
Topic overviewProperties of electromagnetic wavesInvestigating refraction in glass blocksThe groups of the electromagnetic spectrumThe continuous spectrum, and what our eyes can detectHow radiation is generated, and why danger rises with frequencyHarmful effects of excessive exposure to radiationUses of electromagnetic radiation
Radioactivity
Topic overviewThe atom and the size of atomsIsotopes, atomic number and mass numberRelative masses and charges of subatomic particlesElectron orbits and energy levelsForming ions, and how the atomic model changedTypes of ionising radiationBackground radiation and detecting radioactivityAlpha, beta and gamma, and their penetrating powerBeta-minus and beta-plus decayEffects of decay on atomic number and mass numberBalancing nuclear equationsActivity and the becquerelHalf-life and the randomness of decayHalf-life calculationsThe dangers of ionising radiationSafety precautions, contamination and irradiation
Energy – Forces Doing Work
Topic overviewEnergy stores and energy transfer diagramsChanging a system's energy, and measuring work doneWork done and the energy changes it causesGravitational potential and kinetic energy calculationsDissipation and wasted energyPower as the rate of energy transferThe watt, and calculating efficiency
Forces and Their Effects
Electricity and Circuits
Topic overviewThe atom, and drawing circuit diagramsSeries and parallel circuitsPotential difference and the voltmeterEnergy transferred by moving chargeCurrent, charge and measuring currentResistance and the equation V = IRResistors in series and in parallelDesigning circuits to test componentsInvestigating resistance in circuitsCurrent-potential difference graphs for componentsLight-dependent resistors and thermistorsThe heating effect of an electric currentUses of the heating effect, and the equation E = IVtPower as energy transferred per secondCalculating electrical powerEnergy transfer in domestic devices, and power ratingsDirect and alternating currentAlternating current and the UK mains supplyLive and neutral wires, earthing and fusesFuses in the live wire, mains voltages and electrical dangers
Magnetism and the Motor Effect
Electromagnetic Induction
Particle Model
Topic overviewKinetic theory and differences in densityCalculating density, and investigating itChanges of state and internal energySpecific heat capacitySpecific latent heat and thermal insulationInvestigating the specific heat capacity of waterGas pressure and the motion of particlesAbsolute zero and the kelvin scale
Radioactivity
Activity and the becquerel
- 3 things to know
- Paper 5
Overview
Activity as the number of nuclei decaying each second, why it falls over time and the shape of its graph, the becquerel and what 1 Bq means, and calculating decays or activity from counts over a time.
What you need to know
Answer each one before you reveal it.
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Key term
Describe how the activity of a radioactive source changes over a long period of time.
Key term
Explain why the activity of a radioactive source decreases with time.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by the activity of a radioactive source?
Model answer
Activity is the number of nuclei in the source that decay each second.
- 2
Describe how the activity of a radioactive source changes over a long period of time.
Model answer
The activity falls, quickly at first and then more and more slowly.
- 3
Explain why the activity of a radioactive source decreases with time.
Model answer
The number of undecayed nuclei left falls, so fewer nuclei decay each second.
- 4
What shape is a graph of activity against time for a radioactive source?
Model answer
It is a curve that falls steeply at first and then flattens out.
- 5
Does the activity of a radioactive source ever fall to exactly zero?
Model answer
The curve gets closer and closer to zero without reaching it, though in practice the activity becomes too small to measure.
- 6
What is the unit of activity of a radioactive isotope?
Model answer
The becquerel, Bq.
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