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
Resistance
- 9 subtopics
- 27 things to know
- Component 2
What Resistance covers
Resistance is examined in Component 2, Electricity and the Universe. It covers potential difference and the volt, resistance, Ohm's law and the ohm, I–V characteristics of a metal wire and a filament lamp, electrical power and energy transfer, the microscopic origin of resistance, resistivity and the equation R = ρl/A, resistance and temperature, superconductivity and the transition temperature and high temperature superconductors and their uses.
The 9 subtopics
Each one has its own page.
- Potential difference and the voltRecall questions on the definition of potential difference as work done per unit charge, the volt, expressing it in base units, worked calculations of energy transferred, and the difference between potential difference and electromotive force.Open →
- Resistance, Ohm's law and the ohmResistance of a component, defining equation for resistance, giving every symbol and its unit and ohm's law.Open →
- I–V characteristics of a metal wire and a filament lampShape of the I–V characteristic of a filament lamp and curvature of the I–V characteristic of a filament lamp.Open →
- Electrical power and energy transferRecall questions on P = IV and the derived forms I²R and V²/R, choosing the right form for the data given, worked power and energy calculations, the kilowatt hour, and why the power dissipated quadruples when the current doubles.Open →
- The microscopic origin of resistanceRecall questions on what causes resistance in terms of the interaction between drifting electrons and the vibrating lattice, why energy is transferred as heat, how the effect depends on temperature, and why a thicker or shorter conductor has less resistance.Open →
- Resistivity and the equation R = ρl/AResistivity of a material and typical value for the resistivity of copper at room temperature.Open →
- Resistance and temperatureRecall questions on how the resistance of a metal changes with temperature and why, the opposite behaviour of a thermistor, the shapes of both graphs, the experiment with a water bath, and two practical uses of a thermistor.Open →
- Superconductivity and the transition temperatureSuperconducting transition temperature and transition temperature range typical of ordinary metallic superconductors.Open →
- High temperature superconductors and their usesHigh temperature superconductor, boiling point of nitrogen in degrees Celsius and in kelvin and two applications of superconductors.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
State the defining equation for resistance, giving every symbol and its unit.
Key term
State the equation for the power dissipated in a component in terms of current and potential difference.
Key term
State the equation for the resistance of a uniform wire in terms of resistivity, defining every symbol and its unit.
Key term
Outline how the resistivity of a metal in the form of a wire is determined experimentally.
Key term
Why is the diameter of the wire measured at several places along it in a resistivity experiment?
Key term
For a graph of current against potential difference, what does the gradient at a point represent?
Key term
Explain, in terms of electrons and ions, why a metal has electrical resistance.
Key term
How does the resistance of a metal wire vary with temperature over a wide range?
Key term
What is meant by superconductivity?
Key term
What is meant by a high temperature superconductor?
Key term
Define the potential difference between two points in a circuit.
Key term
Define the resistance of a component.
Key term
Why does the I–V characteristic of a filament lamp still pass through the origin?
Key term
Show how P = IV follows from the definitions of current and potential difference.
Key term
What happens to the energy an electron loses when it collides with a lattice ion?
Key term
Why does the resistance of a metal increase as its temperature rises?
Key term
Define the superconducting transition temperature.
Key term
Why is a transition temperature above 77 K such an important threshold?
Key term
Express the volt in terms of the joule and the coulomb.
Key term
Express the ohm in terms of the volt and the ampere.
Key term
Outline how the I–V characteristic of a metal wire at constant temperature is obtained experimentally.
Key term
State the two forms of the power equation that use resistance.
Key term
Why does a current-carrying resistor get hot?
Key term
What is the shape of a graph of resistance against temperature for a metal wire, and what is the significance of its gradient?
Key term
What happens to the resistance of a superconductor as it is cooled through its transition temperature?
Key term
Give an approximate transition temperature for a ceramic high temperature superconductor.
Take Resistance further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
Define the potential difference between two points in a circuit.
Model answer
The potential difference between two points is the energy transferred from electrical form to other forms per unit charge passing between them.
- 2
State the equation for potential difference in terms of energy and charge, defining every symbol and its unit.
Model answer
The equation is V = W/Q, where V is the potential difference in volts (V), W is the energy transferred in joules (J) and Q is the charge that passes in coulombs (C).
- 3
Express the volt in terms of the joule and the coulomb.
Model answer
One volt is one joule per coulomb, so V = J C⁻¹.
- 4
A component transfers 12 J of energy when 4.0 C of charge passes through it. Calculate the potential difference across it.
Model answer
The potential difference is V = 12 J ÷ 4.0 C = 3.0 V. Multiplying 3.0 V by 4.0 C returns the 12 J given.
- 5
A charge of 20 C passes through a resistor with 3.0 V across it. Calculate the energy transferred.
Model answer
The energy is W = QV = 20 C × 3.0 V = 60 J. Dividing 60 J by 20 C returns the 3.0 V given.
- 6
Why must a voltmeter be connected in parallel with a component?
Model answer
A voltmeter measures the energy given up per unit charge between two points, so it must be connected across those two points.
What is inside Levo
Six ways to work the same material.
Resistance revision questions
- What does Resistance cover in Eduqas A-Level Physics?
- 9 subtopics: potential difference and the volt, resistance, ohm's law and the ohm, i–v characteristics of a metal wire and a filament lamp, electrical power and energy transfer, the microscopic origin of resistance, resistivity and the equation r = ρl/a, resistance and temperature, superconductivity and the transition temperature and high temperature superconductors and their uses. Each one has its own page with questions and model answers.
- How is Resistance organised?
- By the Eduqas A420QS specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in 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.
Or £46 a year, about £3.83 a month. Cancel anytime.