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
Energy
Energy changes on heating, and calculating them
- 3 things to know
- Paper 12 (Physics)
Overview
What heating does to the thermal store of a system, specific heat capacity and why water warms slowly, work done by a force against friction and in a heater filament, and calculations of work done, energy transferred electrically, energy to change temperature, and kilowatt-hours and their cost.
What you need to know
Answer each one before you reveal it.
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Key term
What is meant by the specific heat capacity of a substance?
Key term
Two blocks of equal mass but different materials are given the same amount of energy. Which one reaches the higher temperature?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What happens to the energy of a system when it is heated?
Model answer
Its thermal store increases, which normally raises its temperature.
- 2
What is meant by the specific heat capacity of a substance?
Model answer
The energy needed to raise the temperature of 1 kg of the substance by 1 °C.
- 3
Two blocks of equal mass but different materials are given the same amount of energy. Which one reaches the higher temperature?
Model answer
The block made of the material with the smaller specific heat capacity.
- 4
Why does a pan of water take much longer to warm up than the metal pan holding it?
Model answer
Water has a much higher specific heat capacity, so far more energy is needed for each degree of temperature rise.
- 5
What is meant by work done by a force?
Model answer
The energy transferred when a force moves an object through a distance in the direction of the force.
- 6
A heavy box is dragged at a steady speed across a rough floor. Describe the energy change taking place.
Model answer
Work is done against friction, transferring energy to the thermal stores of the box, the floor and the surrounding air.
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