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Cambridge International A Level - fields

A-Level Physics fields

Field models explain interaction without contact. Compare gravitational, electric, and magnetic cases through the same questions: what creates the field, what experiences force, which quantities are vectors, which are scalars, and how does the geometry shape the result?

Framework
Cambridge Physics 9702
Level
Cambridge International A Level Physics
Guide format
Comparative field-model guide

Start with the model

Build one field language, then respect the differences.

Gravitational and electric fields both use inverse-square point-source models and scalar potentials, which makes comparison powerful. The signs differ: mass is positive in the course model, while electric charge can be positive or negative. Field strength and force are vectors; potential and potential energy are scalars.

Magnetic force behaves differently because it depends on motion or current and is perpendicular to the relevant directions. It can bend a charged particle without changing its speed when the force remains perpendicular to velocity. Use diagrams and direction rules as physical models, not as isolated hand gestures.

Study pathway

Four decisions that organize the topic.

Follow the sequence or open the step that matches your current gap. Destination pages keep their existing access rules.

  1. 01

    Compare source models

    Identify mass, charge, or current as the source and state what test object responds.

    Open this step
  2. 02

    Separate field and potential

    Use vector field strength for force and scalar potential for energy changes.

    Open this step
  3. 03

    Use geometry and superposition

    Resolve vectors, add signed potentials, and exploit symmetry before calculating.

    Open this step
  4. 04

    Model magnetic motion

    Connect field direction, charge sign, velocity, and circular-path reasoning.

    Open this step

Use it deliberately

A cross-field comparison table

For each problem, make a small table before solving. The comparison prevents electric and gravitational analogies from being pushed too far.

  1. 01

    Name the source, the test object, the field quantity, and the force relationship.

  2. 02

    Label each quantity vector or scalar and decide how multiple sources combine.

  3. 03

    Write the distance dependence and reference choice for potential where needed.

  4. 04

    Predict direction and limiting behaviour before calculating the magnitude.

Continue on GioPhysics

A mapped route, not a search-results wall.

Curriculum context on this page is public. Lessons, presentations, files, and practice follow the access message shown when you open them.

GravityGravitational fields directoryStudy field strength, potential, orbits, and energy in the gravitational model.ElectricElectric fields directoryStudy Coulomb force, field, potential, equipotentials, and plates.MagneticMagnetism directoryStudy magnetic fields, forces, currents, and charged-particle motion.CombineField superposition and null pointsPractise vector addition and geometric direction checks.PractiseElectric-field applicationsApply field strength, force, potential, and motion models.

Questions before you begin

Clear scope, honest expectations.

Why compare gravitational and electric fields?

Both use point-source inverse-square field models and scalar potentials. Comparing them highlights shared mathematics while charge sign and force direction reveal important differences.

Can a magnetic field speed up a charged particle?

A magnetic force alone is perpendicular to the particle's velocity, so it changes direction rather than speed. An electric field can change kinetic energy.

What should I sketch for a fields question?

Sketch sources, the point of interest, coordinate or radial directions, field or force arrows, relevant distances, and any symmetry before choosing equations.