Key term
OCR A-Level Physics A H556
Practical Skills in the Written Papers
The Practical Endorsement
Topic overviewAnalogue and digital measuring instrumentsImproving accuracy with repeat timing, fiducial markers and plumb linesTiming, calipers and micrometersConstructing and testing circuitsSignal generators and oscilloscopesGenerating and measuring wavesData loggers, modelling software and ionising radiation
Physical Quantities and Units
Making Measurements and Analysing Data
Nature of Quantities
Motion
Forces in Action
Work, Energy and Power
Materials
Newton’s Laws of Motion and Momentum
Charge and Current
Energy, Power and Resistance
Electrical Circuits
Waves
Topic overviewProgressive waves and their propertiesThe wave equationReflection, refraction and diffractionWave graphs and intensityThe electromagnetic spectrumPolarisationRefraction and refractive indexCritical angle and total internal reflectionThe principle of superpositionInterference, coherence and path differenceTwo-source interference, Young's double-slit experiment and the diffraction gratingForming stationary wavesStationary waves on strings and in air columnsMeasuring the speed of soundNode spacing, amplitude and phase in stationary wavesHarmonics and the fundamental mode
Quantum Physics
Thermal Physics
Topic overviewThermal equilibrium and absolute temperatureThe kinetic model of solids, liquids and gasesBrownian motion and internal energySpecific heat capacityMeasuring specific heat capacitySpecific latent heatMeasuring specific latent heatMoles, the Avogadro constant and kinetic theoryGas laws, the ideal gas equation and r.m.s. speedMaxwell-Boltzmann distribution, Boltzmann constant and internal energy
Oscillations
Gravitational Fields
Astrophysics and Cosmology
Topic overviewThe solar system and the birth of a starThe death of a low-mass starSupernovae, neutron stars and black holesThe Hertzsprung-Russell diagramEnergy levels and emission spectraAbsorption spectra and spectral linesPhoton energy and the diffraction gratingWien's law and Stefan's lawAstronomical distances, parallax and the cosmological principleDoppler shift and Hubble's lawThe expanding universe and the Big BangEvidence for the Big Bang and dark energy
Capacitors
Topic overviewCapacitance and charging a capacitorCapacitors in seriesCapacitors in parallel and combined circuitsEnergy stored by a capacitorCharging and discharging through a resistorInvestigating capacitor dischargeThe time constantIterative modelling, exponential decay and the constant-ratio property
Electric Fields
Electromagnetism
Nuclear and Particle Physics
Topic overviewAlpha-particle scattering and the nuclear modelProton number, nucleon number and isotopesThe strong nuclear force and nuclear radiusParticles, antiparticles and hadronsLeptons and the quark modelQuark composition and chargesBeta decay in the quark modelRadioactive decay and the three radiationsNuclear decay equationsActivity, decay constant and half-lifeExponential decay and radioactive datingMass-energy equivalenceAnnihilation, mass defect and binding energyBinding energy per nucleon and induced fissionThe fission reactor and nuclear wasteNuclear fusion and balancing nuclear equations
Energy, Power and Resistance
- 8 subtopics
- 24 things to know
- Papers 2 and 3
What Energy, Power and Resistance covers
Circuits from the component upwards: the symbols and diagrams, e.m.f. and potential difference, Ohm's law and the components that disobey it, resistivity, and electrical power.
Where it is assessed
Papers 2 and 3
Electrons, waves and photons, examined on Exploring Physics and Unified Physics.
Check the OCR specification ↗The 8 subtopics
Each one has its own page.
- Circuit symbols and diagramsRecall questions on the standard symbols and on reading and drawing a circuit diagram.Open →
- Potential difference and e.m.f.Recall questions on the volt, and on what distinguishes the e.m.f. of a source from a potential difference across a component.Open →
- Energy transfer in circuitsRecall questions on W = VQ and W = EQ, and on the energy gained by a charge accelerated through a potential difference.Open →
- Ohm's law and I-V characteristicsRecall questions on resistance and its unit, Ohm's law, R = V/I calculations, ohmic and non-ohmic components, the I-V characteristic of a resistor, and investigating I-V characteristics with a potential divider and spreadsheet.Open →
- Filament lamps, diodes, thermistors and LDRsRecall questions on why filament lamp resistance rises with current, NTC thermistors and their non-linear I-V characteristic, diodes and LEDs and their I-V characteristics, and how LDR resistance changes with light intensity.Open →
- Resistivity and how it is measuredRecall questions on resistivity as a material property, R = ρL/A, its unit and calculations, and measuring the resistivity of a wire: instruments, cross-sectional area from diameter and repeated diameter readings.Open →
- How resistivity varies with temperatureRecall questions on how the resistivity of metals and semiconductors changes with temperature and why, negative temperature coefficients, and NTC thermistors as temperature sensors.Open →
- Electrical power and the kilowatt-hourRecall questions on the three expressions for power, energy transferred as VIt, and calculating a domestic bill.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe the I–V characteristic of a resistor maintained at constant temperature, and explain why the resistance of a filament lamp increases as the current through it increases.
Numbers
State the equations for power dissipated in a component in terms of current and potential difference, and in terms of current and resistance.
Numbers
What does each symbol represent in the equations P = I²R and P = V²/R?
Numbers
What does each symbol represent in W = Pt and in W = VIt, and how is the kilowatt-hour defined?
Key term
What does the circuit symbol for a capacitor look like?
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Define potential difference between two points in a circuit.
Key term
What is the SI unit of resistance?
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Describe the behaviour of a diode with respect to current flow direction.
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What measurements are recorded when investigating the I–V characteristic of a component?
Numbers
State the equation that relates the resistance of a conductor to its resistivity, length, and cross-sectional area.
Key term
Compare how the resistivity of a semiconductor responds to temperature change versus how a metal responds.
Key term
Explain why the resistivity of semiconductors decreases as temperature rises.
Key term
What is the SI unit of potential difference, and what does it represent in base units?
Key term
The symbol E is used for e.m.f. Name three other quantities that also use the symbol E, which must not be confused with e.m.f.
Key term
When we say a component has a p.d. across it, in which direction is energy being transferred?
Numbers
Calculate the cross-sectional area when diameter = 0.001 m.
Key term
Describe the circuit symbol for a cell, identifying which terminal each part represents.
Key term
Express the volt in terms of joules and coulombs.
Key term
State the equation relating energy transferred, potential difference, and charge.
Key term
State Ohm's law.
Key term
How is resistance defined in terms of potential difference and current?
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In the equation R = ρL/A, what does each symbol represent?
Key term
How does the resistivity of a semiconductor change as its temperature increases?
Take Energy, Power and Resistance further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Resistance vs Resistivity
Resistance: potential difference divided by current. Resistivity: material property linking opposition to current with conductor geometry.
Power vs The kilowatt-hour
Power: rate at which work is done. The kilowatt-hour: the energy transferred by a 1 kW device operating for 1 hour.
Questions from this topic
Each one with the model answer underneath.
- 1
Describe the circuit symbol for a cell, identifying which terminal each part represents.
Model answer
A long line (positive terminal) and a short line (negative terminal) drawn parallel to each other.
- 2
How does the circuit symbol for a battery differ from that of a single cell?
Model answer
A battery symbol shows two or more cells in series, represented as alternating long and short parallel lines, whereas a cell has just one pair.
- 3
What does the circuit symbol for an open switch look like?
Model answer
A break in the line with a small angled line showing the switch contact that is not making connection.
- 4
Describe the circuit symbol used for a fixed resistor.
Model answer
A rectangular box.
- 5
How is a variable resistor distinguished from a fixed resistor in a circuit diagram?
Model answer
A variable resistor is shown as a rectangular box with an arrow passing through it diagonally.
- 6
What features identify the circuit symbol for a thermistor?
Model answer
A rectangular box with a diagonal line through it and the temperature symbol (θ or T) placed nearby.
What is inside Levo
Six ways to work the same material.
Energy, Power and Resistance revision questions
- What does Energy, Power and Resistance cover in OCR A-Level Physics A?
- 8 subtopics: circuit symbols and diagrams, potential difference and e.m.f., energy transfer in circuits, ohm's law and i-v characteristics, filament lamps, diodes, thermistors and ldrs, resistivity and how it is measured, how resistivity varies with temperature and electrical power and the kilowatt-hour. Each one has its own page with questions and model answers.
- How is Energy, Power and Resistance organised?
- By the OCR H556 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Energy, Power and Resistance, 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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