What are the two sources that can produce magnetic fields?

Moving charges and permanent magnets.

What do magnetic field lines represent in terms of direction and strength?

Magnetic field lines show the direction of the field (tangent to the line at any point) and their spacing indicates relative strength—closer lines mean a stronger field.

What does the magnetic field pattern of a flat circular coil resemble?

It resembles the field of a short bar magnet, with field lines emerging from one face and entering the other.

OCR A-Level Physics A H556

Practical Skills in the Written Papers

Topic overview Planning an experiment Implementing and recording Processing and interpreting data Plotting and interpreting graphs Evaluating results and procedures Mathematical skills and notation

The Practical Endorsement

Topic overview Analogue and digital measuring instruments Improving accuracy with repeat timing, fiducial markers and plumb lines Timing, calipers and micrometers Constructing and testing circuits Signal generators and oscilloscopes Generating and measuring waves Data loggers, modelling software and ionising radiation

Physical Quantities and Units

Topic overview Physical quantities, estimation and unit conversions S.I. base and derived units Prefixes, homogeneity and labelling conventions

Making Measurements and Analysing Data

Topic overview Systematic and random errors Precision, accuracy and uncertainties

Nature of Quantities

Topic overview Scalars and vectors Adding and resolving vectors

Motion

Topic overview Displacement, speed, velocity and acceleration Motion graphs and the equations of motion Measuring g and investigating motion experimentally Free fall, reaction time and stopping distance Projectile motion

Forces in Action

Topic overview Newton's second law and weight Drag and the factors affecting it Terminal velocity Moments, couples and equilibrium Density, pressure and upthrust

Work, Energy and Power

Topic overview Work done and conservation of energy Kinetic and gravitational potential energy Power and efficiency

Materials

Topic overview Hooke's law and springs Force-extension graphs and work done Elastic potential energy, stress and strain The Young modulus Stress-strain graphs and material behaviour

Newton’s Laws of Motion and Momentum

Topic overview Newton's three laws and linear momentum Force as rate of change of momentum Impulse and force-time graphs Conservation of momentum and collisions

Charge and Current

Topic overview Electric current and the coulomb Elementary charge, charge carriers and Kirchhoff's first law Mean drift velocity

Energy, Power and Resistance

Topic overview 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 Electrical power and the kilowatt-hour

Electrical Circuits

Topic overview Kirchhoff's laws and combining resistances E.m.f., internal resistance and lost volts Potential dividers

Waves

Topic overview Progressive waves and their properties The wave equation Reflection, refraction and diffraction Wave graphs and intensity The electromagnetic spectrum Polarisation Refraction and refractive index Critical angle and total internal reflection The principle of superposition Interference, coherence and path difference Two-source interference, Young's double-slit experiment and the diffraction grating Forming stationary waves Stationary waves on strings and in air columns Measuring the speed of sound Node spacing, amplitude and phase in stationary waves Harmonics and the fundamental mode

Quantum Physics

Topic overview Photons, electronvolts and the Planck constant from LEDs Demonstrating the photoelectric effect Work function and Einstein's equation Electron diffraction The de Broglie equation

Thermal Physics

Topic overview Thermal equilibrium and absolute temperature The kinetic model of solids, liquids and gases Brownian motion and internal energy Specific heat capacity Measuring specific heat capacity Specific latent heat Measuring specific latent heat Moles, the Avogadro constant and kinetic theory Gas laws, the ideal gas equation and r.m.s. speed Maxwell-Boltzmann distribution, Boltzmann constant and internal energy

Circular Motion

Topic overview Radians, angular velocity and period Centripetal force and acceleration

Oscillations

Topic overview Describing simple harmonic motion The defining equation of simple harmonic motion and timing oscillations Velocity, period and graphical relationships Energy in a simple harmonic oscillator Damping, forced oscillations and resonance

Gravitational Fields

Topic overview Gravitational fields and field strength Newton's law of gravitation Field strength of a point mass and the uniform field near Earth Kepler's laws and orbital motion Orbital period and geostationary orbits Gravitational potential Gravitational potential energy and escape velocity

Astrophysics and Cosmology

Topic overview The solar system and the birth of a star The death of a low-mass star Supernovae, neutron stars and black holes The Hertzsprung-Russell diagram Energy levels and emission spectra Absorption spectra and spectral lines Photon energy and the diffraction grating Wien's law and Stefan's law Astronomical distances, parallax and the cosmological principle Doppler shift and Hubble's law The expanding universe and the Big Bang Evidence for the Big Bang and dark energy

Capacitors

Topic overview Capacitance and charging a capacitor Capacitors in series Capacitors in parallel and combined circuits Energy stored by a capacitor Charging and discharging through a resistor Investigating capacitor discharge The time constant Iterative modelling, exponential decay and the constant-ratio property

Electric Fields

Topic overview Electric fields and field lines Coulomb's law and electric field strength Uniform fields, parallel plates and permittivity Electric potential Electric potential energy and capacitance of a sphere

Electromagnetism

Topic overview Magnetic fields and field patterns Fleming's left-hand rule and the motor effect Magnetic flux density and the tesla Charged particles in magnetic fields Magnetic flux, flux linkage and Faraday's law Transformers and the a.c. generator

Nuclear and Particle Physics

Topic overview Alpha-particle scattering and the nuclear model Proton number, nucleon number and isotopes The strong nuclear force and nuclear radius Particles, antiparticles and hadrons Leptons and the quark model Quark composition and charges Beta decay in the quark model Radioactive decay and the three radiations Nuclear decay equations Activity, decay constant and half-life Exponential decay and radioactive dating Mass-energy equivalence Annihilation, mass defect and binding energy Binding energy per nucleon and induced fission The fission reactor and nuclear waste Nuclear fusion and balancing nuclear equations

Medical Imaging

Topic overview The X-ray tube X-ray attenuation and imaging CAT scanning Medical tracers and the gamma camera PET scanning Ultrasound and the piezoelectric transducer Acoustic impedance and reflection Doppler ultrasound

Electromagnetism

6 subtopics
18 things to know
Papers 1, 2 and 3

What Electromagnetism covers

Magnetic fields and what moves in them: the motor effect, charged particles in a field, magnetic flux and Faraday's law, and the transformer.

Where it is assessed

Papers 1, 2 and 3

Newtonian world, astrophysics and particles, drawn on across the papers.

Check the OCR specification ↗

The 6 subtopics

Each one has its own page.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

In the current-balance experiment, why is the balance zeroed first, what is recorded when current flows, and how is the force on the wire calculated?

Numbers

What is the SI unit of magnetic flux density, and what are the force on a charged particle moving perpendicular to a magnetic field and the radius of its circular path?

Numbers

Define magnetic flux and state its formula.

Numbers

Write the equation for induced e.m.f. that combines Faraday's and Lenz's laws, and explain the significance of the negative sign.

Key term

In a simple transformer, what is connected to the primary coil?

Numbers

For an ideal transformer, state the relationship between input and output power.

Key term

How do permanent magnets produce a magnetic field?

Key term

Describe the shape of the magnetic field pattern around a long straight wire carrying a current.

Key term

In Fleming's left-hand rule, what does the first finger represent?

Numbers

State the formula for the force on a charged particle moving perpendicular to a magnetic field and define each term.

Key term

State the equation for the radius of the circular path of a charged particle in a magnetic field.

Key term

Define one weber in terms of tesla and square metre.

Key term

Describe the magnetic field inside a long solenoid.

Key term

In Fleming's left-hand rule, what does the thumb represent?

Numbers

Calculate the selected velocity when electric field strength = 9.1 × 10⁴ V m⁻¹, magnetic flux density = 0.02 T.

Key term

In a velocity selector, how are the electric and magnetic fields oriented relative to each other and to the particle's velocity?

Key term

Define magnetic flux linkage for a coil.

Key term

State the transformer equation relating voltages and turns for an ideal transformer.

Take Electromagnetism further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

Magnetic flux vs Magnetic flux linkage
Magnetic flux: the product of flux density and the area perpendicular to it. Magnetic flux linkage: that product multiplied by the number of turns in the coil.
Faraday's law vs Lenz's law
Faraday's law: the induced e.m.f. is proportional to the rate of change of flux linkage. Lenz's law: the induced effect always opposes the change producing it.
Fleming's left-hand rule vs Fleming's right-hand rule
Fleming's left-hand rule: the rule giving the direction of force on a current in a magnetic field. Fleming's right-hand rule: the rule giving the direction of an induced current in a moving conductor.

Questions from this topic

Each one with the model answer underneath.

1
What are the two sources that can produce magnetic fields?
Model answer
Moving charges and permanent magnets.
2
How do permanent magnets produce a magnetic field?
Model answer
Permanent magnets produce magnetic fields due to the alignment of magnetic domains within the material, arising from electron spin and orbital motion.
3
What do magnetic field lines represent in terms of direction and strength?
Model answer
Magnetic field lines show the direction of the field (tangent to the line at any point) and their spacing indicates relative strength—closer lines mean a stronger field.
4
Describe the shape of the magnetic field pattern around a long straight wire carrying a current.
Model answer
The field lines form concentric circles centred on the wire, lying in planes perpendicular to the wire.
5
What does the magnetic field pattern of a flat circular coil resemble?
Model answer
It resembles the field of a short bar magnet, with field lines emerging from one face and entering the other.
6
Describe the magnetic field inside a long solenoid.
Model answer
The field inside is uniform and parallel to the axis of the solenoid.

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The Practical Endorsement

Physical Quantities and Units

Making Measurements and Analysing Data

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Electromagnetism revision questions

What does Electromagnetism cover in OCR A-Level Physics A?: 6 subtopics: magnetic fields and field patterns, fleming's left-hand rule and the motor effect, magnetic flux density and the tesla, charged particles in magnetic fields, magnetic flux, flux linkage and faraday's law and transformers and the a.c. generator. Each one has its own page with questions and model answers.
How is Electromagnetism organised?: By the OCR H556 specification, subtopic by subtopic, so it matches the order you are taught it in.

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