Key term
OCR GCSE Physics A J249
Electricity
Topic overviewCharge, and producing static electricityTransfer of electrons, and electric fieldsCurrent 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, and calculating efficiencyReducing 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 lawNewton's second lawForce and the time taken to change velocityWork done, and stored energyPower, and Newton's third lawStretching, 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 strengthTurning forces and the moment of a forceLevers and gearsPressure in fluids, and the force on a surface
Global Challenges
Topic overviewTypical speeds and everyday accelerationsReaction time, stopping distance and the dangers of large decelerationsEstimating stopping distances and the forces in a collisionEnergy 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 dangerRed-shift and the Big BangThe formation of the Sun, and radiation from bodiesThe solar system
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 pressureCompressing a gas, and changing its volumeAtmospheric pressure and why it varies with height
Radioactivity
Topic overviewProtons, neutrons and isotopesUnstable nuclei and the emissions they give outBalancing nuclear equationsElectron energy levels, and radiation from atomsHalf-life and the randomness of decayPenetration of alpha, beta and gammaContamination and irradiation, and half-life as a hazardUses of nuclear radiationNuclear fission and fusion
Waves in Matter
Topic overviewAmplitude, wavelength, frequency and periodThe wave equationTransverse and longitudinal wavesSound crossing a boundary; reflection, transmission and absorptionModelling 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 raysRay diagrams for reflection and refractionHow colour arises
Radioactivity
Protons, neutrons and isotopes
- 3 things to know
- Paper 2
Overview
The particles in a nucleus and their charges and masses, what nucleons are, what an isotope is, and how mass number and atomic number give the neutron count and nuclear charge.
What you need to know
Answer each one before you reveal it.
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Key term
What is the relative charge of a proton and what is the relative charge of a neutron?
Key term
Which count of particles in the nucleus gives an element its characteristic positive charge?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which two kinds of particle make up the nucleus of an atom?
Model answer
The nucleus is made of protons and neutrons.
- 2
What is the relative charge of a proton and what is the relative charge of a neutron?
Model answer
A proton has a relative charge of +1 and a neutron has no charge at all.
- 3
Why does the nucleus of every atom carry a positive charge?
Model answer
It contains positively charged protons, and the neutrons alongside them are neutral, so the overall nuclear charge is positive.
- 4
Which count of particles in the nucleus gives an element its characteristic positive charge?
Model answer
The number of protons, because each proton contributes a charge of +1.
- 5
The nucleus of a boron atom carries a charge of +5. How many protons does it contain?
Model answer
It contains five protons.
- 6
What name is given to the protons and neutrons of a nucleus taken together?
Model answer
They are called nucleons.
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