Key term
Eduqas A-Level Physics A420QS
Basic Physics
Kinematics
Dynamics
Energy Concepts
Circular Motion
Vibrations
Topic overviewDefining simple harmonic motionFrequency, period, amplitude and phaseThe displacement equation for simple harmonic motionVelocity in simple harmonic motionDisplacement and velocity graphsThe mass-spring oscillatorThe simple pendulumEnergy in simple harmonic motionFree oscillation and dampingForced oscillation and resonance
Kinetic Theory
Thermal Physics
Conduction of Electricity
Resistance
Topic overviewPotential difference and the voltResistance, Ohm's law and the ohmI–V characteristics of a metal wire and a filament lampElectrical power and energy transferThe microscopic origin of resistanceResistivity and the equation R = ρl/AResistance and temperatureSuperconductivity and the transition temperatureHigh temperature superconductors and their uses
D.C. Circuits
Capacitance
Solids Under Stress
Electrostatic and Gravitational Fields of Force
Topic overviewElectric field strength and Coulomb's lawGravitational field strength and Newton's law of gravitationField lines and equipotential surfacesElectric potential and potential energyGravitational potential and potential energyResultant fields and potentials from several sourcesComparing electric and gravitational fields
Using Radiation to Investigate Stars
Orbits and the Wider Universe
Topic overviewKepler's laws of planetary motionNewton's law of gravitation applied to planets and satellitesDeriving Kepler's third law for a circular orbitUsing orbital data to find the mass of the central objectGalactic rotation curves and dark matterThe centre of mass of a two-body systemThe Doppler shift of spectral lines and radial velocityMasses in a double system from radial velocity dataHubble's law, the age of the universe and its fate
The Nature of Waves
Wave Properties
Topic overviewDiffraction at slits and obstaclesWavelength, slit width and the spread of the beamThe principle of superpositionCoherence and the conditions for interferencePath difference and the interference conditionsYoung's double slit experimentThe historical importance of Young's experimentThe diffraction gratingComparing the grating with the double slitStationary waves
Refraction of Light
Photons
Topic overviewPhotons and the quantum of lightDemonstrating the photoelectric effectThe vacuum photocell and stopping potentialEinstein's equation and the energy graphThe electromagnetic spectrum and photon energiesLine emission and line absorption spectraAtomic energy levelsIonisation energy from an energy level diagramElectron diffraction and the de Broglie relationship
Lasers
Nuclear Decay
Topic overviewSpontaneous decay and the nature of α, β and γ radiationNuclear transformation equations and nuclide notationDistinguishing α, β and γ by ionisation, penetration and rangeBackground radiation and gamma intensity with distanceActivity, the becquerel and the decay constantThe exponential decay law and half-life
Particles and Nuclear Structure
Topic overviewThe Rutherford alpha particle scattering experimentCoulomb repulsion in the plum pudding and Rutherford modelsQuarks and leptons: the first generationAntiparticles, annihilation and their symbolsHadrons: baryons, antibaryons and mesonsQuark composition of the proton, neutron and pionsThe four fundamental interactionsConservation laws in particle reactions
Nuclear Energy
Magnetic Fields
Topic overviewThe motor effect and Fleming's left-hand ruleF = BIl sinθ and measuring magnetic flux densityThe force on a moving charge, F = Bqv sinθThe Hall effect and the Hall probeMagnetic fields due to a straight wire and a solenoidForces between current-carrying conductorsCharged particle beams and accelerators
Electromagnetic Induction
Option A: Alternating CurrentsOption A
Topic overviewElectromagnetic induction in a rotating coilFrequency, period, peak and rms valuesMean power dissipated in a resistorUsing an oscilloscope to measure voltage and frequencyInductors in a.c. circuits and inductive reactanceCapacitors in a.c. circuits and capacitive reactancePhasors, phase angle and impedanceResonance in the series RCL circuit and the Q factor
Option B: Medical PhysicsOption B
Topic overviewThe nature and properties of X-raysX-ray production and controlling the beamAttenuation of X-rays and half-value thicknessX-ray imaging, fluoroscopy and radiographyComputed tomography scanningUltrasound generation and acoustic impedanceUltrasound scanning and the Doppler techniqueMagnetic resonance and MRIRadiation effects on living matter and dosimetryRadionuclide tracers, the gamma camera and PET
Option C: The Physics of SportsOption C
Topic overviewCentre of gravity, stability and topplingMoments in muscle systems and other sporting contextsImpulse and Newton's second law in sportThe coefficient of restitutionMoment of inertiaAngular acceleration, torque and angular momentumConservation of angular momentum and rotational energyProjectiles, Bernoulli's equation and drag
Option D: Energy and the EnvironmentOption D
Mathematical Requirements (Appendix C)
Topic overviewUnits, prefixes and standard formSignificant figures and arithmetic meansUncertainty and how uncertainties combineRatios, proportionality and order of magnitude estimatesRearranging and solving physics equationsLogarithms, exponentials and decayResolving vectors, Pythagoras and trigonometryRadians, small angles, areas and volumesStraight-line graphs, gradients and interceptsTangents, areas under curves and logarithmic plots
D.C. Circuits
- 7 subtopics
- 21 things to know
- Component 2
What D.C. Circuits covers
D.C. Circuits is examined in Component 2, Electricity and the Universe. It covers current at a junction and conservation of charge, potential difference round a circuit and conservation of energy, resistors in series, resistors in parallel, the potential divider, sensing circuits with LDRs and thermistors and emf and internal resistance.
The 7 subtopics
Each one has its own page.
- Current at a junction and conservation of chargeHow conservation of charge leads to the junction rule and junction rule as an algebraic sum.Open →
- Potential difference round a circuit and conservation of energyRecall questions on the sum of potential differences round a loop, why it equals the electromotive force, the link to conservation of energy, and worked problems finding a missing potential difference in a series or a multi-loop circuit.Open →
- Resistors in seriesRecall questions on the rule that resistances add, its derivation from the shared current and added potential differences, worked calculations, why the total always exceeds the largest resistor, and how the potential difference divides between them.Open →
- Resistors in parallelRecall questions on the reciprocal rule and its derivation from the shared potential difference and added currents, worked calculations, why the total is always less than the smallest resistor, and how the current divides between the branches.Open →
- The potential dividerRecall questions on what a potential divider is, the divider equation and its ratio form, why the supply divides in proportion to the resistances, using a variable resistor as a divider, and worked output calculations including the effect of a load.Open →
- Sensing circuits with LDRs and thermistorsRecall questions on how the resistance of each sensor varies, how the output of a divider containing one changes with light or temperature, the effect of swapping the sensor and the fixed resistor, and worked calculations for a light or frost sensing circuit.Open →
- emf and internal resistanceElectromotive force of a source, unit of electromotive force and internal resistance of a source.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
State the equation relating terminal potential difference, emf, current and internal resistance.
Numbers
Two cells, each of emf 1.5 V and internal resistance 0.50 Ω, are connected in series to a 5.0 Ω resistor. Calculate the current.
Key term
State the rule relating the current from a source to the currents in the branches of a parallel circuit.
Key term
State the rule relating the potential differences across components in series to the supply potential difference.
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State the equation for the combined resistance of resistors connected in series.
Key term
State the equation for the combined resistance of resistors connected in parallel.
Key term
What is a potential divider?
Key term
Explain how conservation of charge leads to the junction rule.
Key term
State the rule for potential differences across components connected in parallel.
Key term
Why is the combined resistance of a series chain always greater than the largest resistance in it?
Key term
Derive the parallel resistance rule from the current and potential difference rules.
Key term
State the potential divider equation for the output taken across the second of two resistors.
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How does the resistance of a light dependent resistor change with the light falling on it?
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Two identical lamps are connected in parallel across a battery. How does the total current from the battery compare with the current through one lamp?
Key term
Two identical lamps in series are connected to a 6.0 V battery. State the potential difference across each.
Numbers
For a 4.0 Ω and a 6.0 Ω resistor in series across 12 V, calculate the potential difference across each.
Key term
Give the shortened form of the parallel rule for exactly two resistors.
Evaluation
What is the advantage of using large resistances in a potential divider?
Key term
Why does the resistance of a light dependent resistor fall in bright light?
Key term
What is the unit of electromotive force?
Take D.C. Circuits further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
State the rule relating the current from a source to the currents in the branches of a parallel circuit.
Model answer
The current drawn from the source equals the sum of the currents in the separate parallel branches.
- 2
Which conservation law is the junction rule for currents a consequence of?
Model answer
It follows from the conservation of electric charge.
- 3
Explain how conservation of charge leads to the junction rule.
Model answer
Charge cannot be created, destroyed or stored at a junction, so charge must leave the junction at exactly the same rate as it arrives.
- 4
A current of 3.0 A enters a junction and 1.2 A leaves along one branch. Calculate the current in the other branch.
Model answer
The other branch carries 3.0 − 1.2 = 1.8 A. Adding 1.8 A and 1.2 A returns the 3.0 A entering.
- 5
Three parallel branches carry 0.40 A, 0.65 A and 0.95 A. Calculate the current drawn from the supply.
Model answer
The supply current is 0.40 + 0.65 + 0.95 = 2.00 A. Subtracting the 0.65 A and 0.95 A branches from 2.00 A returns 0.40 A.
- 6
Why is the current the same at every point in a series circuit?
Model answer
There is only one path, and since charge cannot accumulate anywhere along it, the same rate of charge flow must pass every point.
What is inside Levo
Six ways to work the same material.
D.C. Circuits revision questions
- What does D.C. Circuits cover in Eduqas A-Level Physics?
- 7 subtopics: current at a junction and conservation of charge, potential difference round a circuit and conservation of energy, resistors in series, resistors in parallel, the potential divider, sensing circuits with ldrs and thermistors and emf and internal resistance. Each one has its own page with questions and model answers.
- How is D.C. Circuits organised?
- By the Eduqas A420QS specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in D.C. Circuits, 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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