Key term
OCR GCSE Combined Science Physics J250
Electricity
Topic overviewCharge, and producing static electricityTransfer of electrons in charging and dischargingCurrent as a rate of flow of chargeCharge, current and timeSeries and parallel circuits, and circuit symbolsCurrent, potential difference and resistanceResistors whose resistance changes, and investigating themLinear and non-linear circuit elements from graphsNet resistance in series and parallelCircuits for measurement, and electrical power
Energy
Topic overviewConservation of energy, and energy storesEnergy changes on heating, and calculating themEnergy of a moving body, a spring and a raised objectDissipation, and energy transfer in domestic devicesPower ratings, efficiency, and increasing itReducing unwanted energy transfer, and the rate of cooling
Forces
Topic overviewMeasuring distance and time, and calculating speedConverting units, and ratesVectors and scalars in motionDistance-time and velocity-time graphsAverage speed, and the equations of uniform motionHow objects interact, and forces as vectorsNewton's first lawResolving forces, and free body diagramsResultant forces, and balanced forcesNewton's second law, and inertiaMomentum and its conservationWork done, and stored energyPower, and Newton's third lawCircular motion and changing velocityStretching, bending and compressing; elastic and plasticForce and extension, linear and non-linearThe spring constant, and work done in stretchingGravitational fields, weight and free fallCalculations with weight and gravitational field strength
Global Challenges
Topic overviewTypical speeds and everyday accelerationsReaction time, stopping distance and the dangers of large decelerationsStopping distance, acceleration and collision force calculationsEnergy resources, and trends in their useThe national grid, and step-up and step-down transformersWhy the national grid is efficient, and power in a transformerMains electricity: a.c., d.c. and the domestic supplyLive, neutral and earth wires, and electrical danger
Magnetism and Magnetic Fields
Matter
Topic overviewHow the atomic model changed, and the structure of the atomThe size of atoms, and defining densityDensity of the states of matter, and density calculationsConservation of mass in changes of stateHeating a system, and specific heat capacityCalculations with specific heat capacity and latent heatGas molecules, temperature and pressure
Radioactivity
Waves in Matter
Topic overviewAmplitude, wavelength, frequency and periodThe wave equationTransverse and longitudinal wavesModelling waves with ripples and soundElectromagnetic waves as transverse, and energy transferFrequency and wavelength across the spectrumWhat our eyes detect, and light as an electromagnetic waveUses of electromagnetic wavesHazards of ultraviolet, X-rays and gamma raysProducing and receiving radio wavesAbsorption, transmission, refraction and reflectionInvestigating reflection and refraction of light
Matter
How the atomic model changed, and the structure of the atom
- 3 things to know
- Paper 11 (Physics)
Overview
The Thomson, Rutherford and Bohr models and Chadwick's neutron, the alpha scattering experiment of Geiger and Marsden and what it showed, the nuclear atom and its size, why models change, and hypotheses, testing theories, peer review and publishing results.
What you need to know
Answer each one before you reveal it.
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Key term
In the alpha particle scattering experiment, what was fired at what?
Key term
Who carried out the alpha particle scattering measurements that Rutherford interpreted?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What did Thomson's model of the atom describe, and which discovery led him to it?
Model answer
It described the atom as a ball of positive charge with tiny negative electrons spread through it, and he proposed it after discovering the electron.
- 2
In the alpha particle scattering experiment, what was fired at what?
Model answer
A narrow beam of alpha particles was fired at an extremely thin sheet of gold foil.
- 3
Who carried out the alpha particle scattering measurements that Rutherford interpreted?
Model answer
Geiger and Marsden, who counted the alpha particles arriving at different angles after passing through the foil.
- 4
What were the two surprising results of the alpha particle scattering experiment?
Model answer
Almost all the alpha particles went straight through the foil, but a very small number were deflected through large angles or came straight back.
- 5
What did Rutherford conclude about the atom from the scattering results?
Model answer
That the atom is mostly empty space, with almost all its mass and all its positive charge in a tiny central nucleus.
- 6
Why could the earlier model of the atom not explain the alpha scattering results?
Model answer
Positive charge spread thinly through the whole atom could never repel a fast alpha particle strongly enough to turn it back, so the charge had to be concentrated.
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