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
Radioactivity
Electron energy levels, and radiation from atoms
- 3 things to know
- Paper 12 (Physics)
Overview
Electrons in energy levels, excitation by absorbing radiation and emission on falling back, ionisation and the positive ion it leaves, the wide range of frequencies atoms and nuclei emit, gamma rays from the nucleus, the spectrum in order of frequency, and what sets the frequency emitted.
What you need to know
Answer each one before you reveal it.
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Key term
What is meant by ionisation of an atom?
Key term
Which part of the electromagnetic spectrum is produced by changes in the nucleus itself?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How are the electrons of an atom arranged around its nucleus?
Model answer
They sit at different distances from the nucleus, in separate energy levels.
- 2
What happens to an electron in an atom that absorbs energy from electromagnetic radiation?
Model answer
It gains energy and moves up to a higher energy level, further from the nucleus.
- 3
What word describes an electron that has absorbed energy and risen to a higher energy level?
Model answer
It is described as excited.
- 4
What happens when an excited electron loses the extra energy it gained?
Model answer
It falls back to a lower energy level and the energy it loses is emitted as electromagnetic radiation.
- 5
What is meant by ionisation of an atom?
Model answer
Ionisation is the loss of one or more of an atom's outer electrons.
- 6
What charge does an atom have once it has lost an outer electron?
Model answer
It has a positive charge, because it then has more protons than electrons.
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