Key term
OCR A-Level Physics B H557
Planning
Implementing
Analysis
Evaluation
Practical Skills
Use of Apparatus and Techniques
Fundamental Data Analysis
Imaging and Signalling
Topic overviewReal images and the curvature of wave-frontsLens power and focal lengthThe thin lens equation and the Cartesian conventionLinear magnificationMeasuring the power and focal length of a converging lensImages as arrays of numbersBits, bytes and the information in an imageEnhancing a digital imageWave-forms, frequency and wave speedSampling and digitising an analogue signalNoise, resolution and digital transmissionPolarisation of electromagnetic waves
Sensing
Topic overviewCurrent and the flow of chargePotential difference, e.m.f. and energy transferResistance, conductance and Ohm's lawSeries and parallel combinationsPower and energy in electric circuitsInternal resistance and e.m.f.Kirchhoff's laws and conservation in circuitsResistivity and conductivityCharge carrier number density in metals, semiconductors and insulatorsCurrent-potential difference characteristics and circuit componentsThe potential dividerSensing circuits and calibration
Mechanical Properties of Materials
Topic overviewElastic and plastic deformation and fractureHooke's law and force-extension graphsElastic strain energyStress, strain and the Young modulusMeasuring the Young modulus and fracture stress of a metalDescribing and comparing materialsMetals, ceramics and polymersDirect evidence for the size and spacing of particles
Waves and Quantum Behaviour
Topic overviewWaves, phase and superpositionStanding waves on stringsStanding waves in air columns and the speed of soundRefraction, refractive index and Snell's lawTwo-slit interferenceDiffraction at a narrow apertureThe diffraction gratingMeasuring the wavelength of lightPhotons and the quantum E = hfEvidence that photons exchange energy in quantaQuantum behaviour: phasors and probability of arrivalElectron diffraction and the de Broglie wavelength
Space, Time and Motion
Topic overviewScalars, vectors and their representationResolving and adding vectorsDescribing motion: displacement, velocity and accelerationMotion graphsThe kinematic equations for constant accelerationProjectiles and motion in two dimensionsMeasuring motion in the laboratoryDetermining the acceleration of free fallNewton's laws of motionTerminal velocity and resistive forcesMomentum and impulseConservation of momentum and collisionsWork, energy and its conservationPower and modelling motion in small time steps
Creating Models
Topic overviewCapacitance and charge storageEnergy stored on a capacitorCapacitor discharge and the exponential modelThe time constant of an RC circuitCharging a capacitorInvestigating capacitor charge and dischargeRadioactive decay as a random processActivity, decay constant and half-lifeDetermining the half-life of an isotopeIterative numerical models of exponential changeExponential curves on linear and logarithmic scalesSimple harmonic motion: the defining relationshipSolutions and graphs of simple harmonic motionModelling oscillations step by stepEnergy in simple harmonic motionPeriod of a mass–spring system and a simple pendulumFree and forced vibrations, damping and resonance
Out Into Space
Topic overviewGravitational and kinetic energy changesMotion in a uniform gravitational fieldGravitational force and the radial fieldGravitational field strengthGravitational potential energy in a radial fieldGravitational potential and equipotentialsGraphs and diagrams of gravitational fieldsAngular velocity and motion in a horizontal circleCircular gravitational orbits
Our Place in the Universe
Matter: Very Simple
Topic overviewEnergy transfer and specific thermal capacityFinding specific thermal capacity by an electrical methodIdeal gases and the gas lawsInvestigating the gas laws and absolute zeroMoles, the Avogadro constant and the Boltzmann constantThe equation of state for an ideal gasImpulse and force–time graphsThe kinetic theory of ideal gasesTemperature, average energy per particle and internal energyRandom walk of molecules in a gas
Matter: Hot or Cold
Electromagnetism
Topic overviewMagnetic flux, B-fields and flux linkageElectromagnetic induction: Faraday's and Lenz's lawsGraphs of current, flux and induced e.m.f.The dynamoThe transformerEddy currents and real transformersForces on current-carrying conductorsMagnetic circuits, permeance and machine designInvestigating induction, flux density and transformers
Charge and Field
Topic overviewThe uniform electric fieldRadial fields and the inverse square lawElectric potential and potential energyField and potential graphsField lines and equipotential surfacesThe electronvolt and accelerating chargesMillikan's experiment and the discreteness of chargeMoving charges in magnetic fieldsComparing electric and gravitational fields
Probing Deep Into Matter
Topic overviewParticle accelerators and high-energy beamsScattering and the nuclear atomPaths of scattered particles and closest approachDiscrete energy levels in atomsElectron standing waves and the confined electronQuarks, hadrons and leptonsConservation laws and nuclear equationsCharged particles in detectors and magnetic fieldsRelativistic energy and the relativistic factor
Ionising Radiation and Risk
Topic overviewThe nature of ionising radiationsEffects on living tissue and radiation safetyAbsorbed dose, effective dose and riskBinding energy and nuclear stabilityThe Nuclear Valley and modes of decayFission, fusion and nuclear powerActivity, half-life and the decay constantInvestigating absorption and half-life
Sensing
- 12 subtopics
- 36 things to know
- Components 01, 02 and 03
What Sensing covers
Sensing is examined in all three written papers — the specification states that Components 01, 02 and 03 each assess content from across all the teaching modules, so nothing is confined to one paper. It covers current and the flow of charge, potential difference, e.m.f. and energy transfer, resistance, conductance and Ohm's law, series and parallel combinations, power and energy in electric circuits, internal resistance and e.m.f., Kirchhoff's laws and conservation in circuits, resistivity and conductivity, charge carrier number density in metals, semiconductors and insulators, current-potential difference characteristics and circuit components, the potential divider and sensing circuits and calibration.
Where it is assessed
Components 01, 02 and 03
Every module can be assessed on any of the three papers.
Check the OCR specification ↗The 12 subtopics
Each one has its own page.
- Current and the flow of chargeRecall questions on current as the rate of flow of charge, I = ΔQ/Δt, the coulomb, charge carriers in metals and electrolytes, counting electrons, conventional current, the same current around a series circuit, why a lamp lights at once, I = nAvq and drift speed in a narrowing wire, and why current is a scalar.Open →
- Potential difference, e.m.f. and energy transferRecall questions on defining potential difference, the volt and e.m.f., the difference between e.m.f. and potential difference, energy transferred per coulomb, and why a voltmeter must have a very high resistance.Open →
- Resistance, conductance and Ohm's lawRecall questions on resistance and conductance and their units, G = 1/R, Ohm's law and ohmic conductors, the ohm, why metal resistance rises and thermistor resistance falls when heated, the current–potential difference graphs of a filament lamp and a diode, and when conductance is more convenient than resistance.Open →
- Series and parallel combinationsRecall questions on combining resistances and conductances in series and in parallel, why a parallel combination has less resistance than its smallest branch, calculating combined resistances and branch currents, mixed series and parallel networks, current dividing in inverse proportion to resistance, and why household appliances are wired in parallel.Open →
- Power and energy in electric circuitsRecall questions on P = IV, P = I²R and P = V²/R, the watt, energy transferred W = VIt, why a resistor heats up, heater, battery and kettle calculations, high-voltage transmission, identical lamps in series, the safe current for a rated resistor, and why a filament glows while its leads stay cool.Open →
- Internal resistance and e.m.f.Recall questions on the internal resistance of a source, terminal potential difference and lost volts, finding internal resistance from a graph, maximum power transfer, and why car batteries need very low internal resistance.Open →
- Kirchhoff's laws and conservation in circuitsRecall questions on Kirchhoff's first and second laws and the conservation of charge and energy they express, finding an unknown branch current and potential difference, why charge does not build up at a junction, signs around a loop, a cell with internal resistance, lamps in parallel, and why the laws hold in any network.Open →
- Resistivity and conductivityRecall questions on R = ρL/A and G = σA/L, the units of resistivity and conductivity, σ = 1/ρ, how length and thickness affect resistance, a copper wire's resistance and conductivity, measuring the resistivity of a wire, measuring its diameter and keeping the current small, stretching a wire, and typical resistivities of conductors and insulators.Open →
- Charge carrier number density in metals, semiconductors and insulatorsRecall questions on the number density of charge carriers in metals, semiconductors and insulators, how heating changes the conductance of a semiconductor and a metal, light-dependent resistors, calculating n = I/(Avq) for copper, tiny drift speeds, why thermistors are made from semiconductors, and insulators at very high temperatures.Open →
- Current-potential difference characteristics and circuit componentsRecall questions on obtaining a current–potential difference characteristic with a potential divider, ohmic lines, finding resistance from a curve rather than its gradient, filament lamp and diode characteristics, thermistor and metal wire temperature graphs, meter placement and self-heating, symbols for thermistors, light-dependent resistors, cells and batteries, reversed readings, and voltmeter current.Open →
- The potential dividerRecall questions on what a potential divider is, Vₒᵤₜ = Vᵢₙ × R₂/(R₁ + R₂), potential difference in proportion to resistance, calculating outputs and resistance ratios, the loading effect and how to minimise it, rotary potentiometers and uniform wires, raising the upper resistance, and why a divider beats a series resistor for outputs from zero.Open →
- Sensing circuits and calibrationRecall questions on sensors, how thermistors and light-dependent resistors respond, potential dividers whose output rises or falls with temperature, calculating outputs with thermistors and light-dependent resistors, the sensitivity of a sensing circuit and choosing its fixed resistor, calibrating a thermistor circuit and why it needs a curve, and response time, resolution and thermal capacity.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe how to determine the internal resistance of a cell experimentally.
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Describe how to determine the resistivity of a metal in wire form.
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Describe how a thermistor sensing circuit would be calibrated.
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Define electric current.
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Define potential difference.
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Define resistance.
Numbers
Calculate the combined resistance of 4.0 Ω and 6.0 Ω in series.
Key term
State Kirchhoff's first law.
Key term
Explain the high conductivity of a metal in terms of number density.
Key term
Describe how to obtain the current–potential difference characteristic of a component.
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What is a potential divider?
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State the relationship between current, charge and time.
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State the relationship for potential difference in terms of work and charge.
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Define conductance and state its unit.
Numbers
Calculate the combined resistance of 4.0 Ω and 6.0 Ω in parallel.
Key term
State three equivalent relationships for the power dissipated in a component.
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State the relationship linking terminal potential difference, e.m.f., current and internal resistance.
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State Kirchhoff's second law.
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State the relationship between resistance, resistivity, length and cross-sectional area.
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Explain why an insulator conducts so poorly.
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Why is a potential divider better than a series rheostat for obtaining a characteristic?
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State the potential divider relationship.
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What is a sensor in an electrical sensing circuit?
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What carries the current in an electrolyte?
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Define the volt.
Numbers
A component carries 0.50 A with 12 V across it. Calculate its resistance and its conductance.
Key term
Explain why the resistance of a parallel combination is always smaller than the smallest resistance in it.
Key term
Define the watt.
Numbers
A cell of e.m.f. 1.5 V and internal resistance 0.50 Ω is connected to a 2.5 Ω resistor. Calculate the current.
Numbers
Currents of 2.0 A and 1.5 A enter a junction, and 0.80 A leaves along one branch. Calculate the current in the remaining branch.
Key term
State the unit of resistivity.
Key term
Explain why the conductance of a semiconductor rises steeply as it is heated.
Key term
How is the resistance found from a point on a curved current–potential difference graph?
Key term
State the proportionality between potential difference and resistance in a series circuit.
Key term
Describe a potential divider arrangement whose output rises as the temperature rises.
Take Sensing further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
E.m.f. vs Terminal potential difference
E.m.f.: the energy a source gives to each coulomb passing through it. Terminal potential difference: The energy each coulomb still carries out into the external circuit, once the lost volts Ir inside the source have been subtracted.
Resistance vs Resistivity
Resistance: the potential difference across a component divided by the current through it, which depends on that sample's length and cross-sectional area. Resistivity: A property belonging to the material alone, measured in ohm metres, and the same whatever the size or shape of the sample.
Ohm's law vs R = V/I
Ohm's law: the claim that the current through a component is directly proportional to the potential difference across it, so their ratio stays constant while temperature and other physical conditions do not change. R = V/I: The potential difference across a component divided by the current through it, a ratio that can be worked out for any component whether or not it stays constant.
Questions from this topic
Each one with the model answer underneath.
- 1
Define electric current.
Model answer
Electric current is the rate of flow of electric charge.
- 2
State the relationship between current, charge and time.
Model answer
I = ΔQ/Δt, giving the current in amperes when the charge is in coulombs and the time in seconds.
- 3
What are the mobile charge carriers in a metal?
Model answer
They are the delocalised, or free, electrons.
- 4
What carries the current in an electrolyte?
Model answer
Positive and negative ions, moving in opposite directions through the solution.
- 5
Define the coulomb.
Model answer
One coulomb is the charge that passes a point when a current of one ampere flows for one second.
- 6
A charge of 240 C passes through a lamp in 2.0 minutes. Calculate the current.
Model answer
I = 240/120 = 2.0 A.
What is inside Levo
Six ways to work the same material.
Sensing revision questions
- What does Sensing cover in OCR A-Level Physics B?
- 12 subtopics: current and the flow of charge, potential difference, e.m.f. and energy transfer, resistance, conductance and ohm's law, series and parallel combinations, power and energy in electric circuits, internal resistance and e.m.f., kirchhoff's laws and conservation in circuits, resistivity and conductivity, charge carrier number density in metals, semiconductors and insulators, current-potential difference characteristics and circuit components, the potential divider and sensing circuits and calibration. Each one has its own page with questions and model answers.
- How is Sensing organised?
- By the OCR H557 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Sensing, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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