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
Electricity
Charge, and producing static electricity
- 3 things to know
- Paper 11 (Physics)
Overview
Positive and negative charge in all matter, zero net charge and the sign of an object that gains or loses electrons, the coulomb, producing static by rubbing, attraction and repulsion without contact, why insulators hold charge, and sparks, car-door shocks and earthing a fuel tanker.
What you need to know
Answer each one before you reveal it.
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Key term
Which particles inside an atom carry negative charge, and which carry positive charge?
Key term
Is charge found only in special materials, or in all matter?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which property of matter exists in a positive form and a negative form?
Model answer
Electric charge.
- 2
Which particles inside an atom carry negative charge, and which carry positive charge?
Model answer
Electrons carry negative charge and protons carry positive charge.
- 3
Is charge found only in special materials, or in all matter?
Model answer
All matter contains charge, because every atom contains positively charged protons and negatively charged electrons.
- 4
What is meant by saying that an object has zero net charge?
Model answer
The total positive charge on the object is equal to the total negative charge, so the two cancel out.
- 5
Why do most everyday objects have no overall charge?
Model answer
They contain equal numbers of positive and negative charges.
- 6
An object has more electrons than protons. What is the sign of its overall charge?
Model answer
Negative, because the negative charge is no longer balanced by the positive charge.
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