IPhO electricity and magnetism
Electrostatics, magnetostatics, and circuit techniques with symmetry and approximation-first thinking for olympiad preparation.
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Before you begin
An IPhO electricity or magnetism problem often becomes manageable once you identify what is fixed and what changes. Symmetry can simplify a field; terminal equivalence can simplify a circuit. The choice still needs a reason: zero enclosed charge does not mean zero local field, and a familiar circuit formula may fail after a switch changes its constraints.
Be comfortable with: A-Level electric fields, current electricity, D.C. circuits, electromagnetic forces and electromagnetic induction, and the IPhO problem-solving framework.
Learning goals
- Apply electricity & magnetism models and problem-solving methods in competition settings.
Lessons
Work through them in order.
Build the bridge
Build the official core
- Capacitance, energy and the method of imagesFind capacitance from geometry, forces from energy, and fields near grounded conductors by the method of images.
- Circuit reduction: Thévenin and NortonReduce a network to its Thévenin or Norton equivalent and check the result with limiting cases.
- Magnetostatics: Ampère's law and the Biot–Savart lawChoose between Ampère's law and Biot–Savart to find magnetic fields and forces quickly.
Transfer to unfamiliar problems
Practise and check
Topic reference
What you should be able to do
- Use symmetry to choose a field method and state why the field has the required direction or constancy.
- Reduce electrostatic and circuit systems using potentials, energy, equivalent sources and time-scale reasoning.
- Apply magnetic-force, Ampere, Biot-Savart and induction ideas with consistent directions, signs and limiting checks.
Official scope: Stages selected electrostatics, circuits and magnetic-field methods from the official electromagnetic-field coverage.
Training habits
- For a field, state the symmetry and direction before choosing a Gaussian surface, an Ampère loop or a vector sum.
- For energy and switching, identify the system boundary, the fixed quantity and the initial state before choosing an equation.
- Check signs and limits, then try the changed-condition tasks with the solutions closed. Numerical checks verify their stated quantities; compare derivations, directions and explanations with the public solutions yourself.