IPhO Electricity & Magnetism Problem Set (Official Problems + Hints)
Curated IPhO E&M problems grouped by technique (symmetry, circuits, magnetostatics, induction), with outlines and common traps.
On this page
E&M at IPhO is usually “geometry + symmetry + the right representation”. This set is built to train that habit.
Before you start
If you have not done the hub path yet, start with the IPhO Electricity & Magnetism Hub.
Source PDFs
Archive mirror index: https://phoxiv.org/contests/ipho
Official documentations page: https://www.ipho-new.org/documentations/
Fading-hint route (recommended order)
Read the framework once: IPhO Problem-Solving Framework
Do the hub Entry and Core lessons first (then return here):
- Start with sections A and B below (starter problems).
- Finish the hub lessons, then do sections C and D (core).
- Do section E (experimental) once per week.
A. Electrostatics and Field Geometry
- IPhO 2021 T2 — “Electrostatic Lens” (PDF)
Outline pattern: symmetry-first electrostatics
- state the symmetry and what components must be zero - choose Gauss or potential, whichever collapses the geometry faster - do a limit check: far away looks like a point object; near a surface you get a local planar approximation
B. Circuits, Nonlinear Dynamics, and Time Scales
- IPhO 2016 T2 — “Nonlinear Dynamics in Electric Circuits” (PDF)
Outline pattern: circuits beyond Thevenin
- reduce what you can (Thevenin/Norton) to isolate one dynamic element - identify the time scale (RC, RL, or an effective time constant from the model)
- nondimensionalise once to reveal the small parameter / dominant balance
C. Magnetostatics and Fields
- IPhO 2022 T1 — “Permanent magnets” (PDF)
- IPhO 2025 E1 — “Measurement of Earth’s magnetic field” (PDF)
Outline pattern: B-fields without over-integrating
- write the symmetry (what stays invariant under rotation/translation) - decide: Ampere loop (high symmetry) or Biot-Savart (localized geometry) - estimate magnitudes first, then refine - check direction with right-hand rules, then check limits
D. EM Waves, Resonances, and Energy Flow
- IPhO 2019 T2 — “Microwave Oven” (PDF)
Outline pattern: waves in E&M problems
- identify what sets the length scale (cavity dimension, wavelength, boundary conditions) - track energy: Poynting/energy balance sanity checks often catch sign mistakes - do an order-of-magnitude first answer before detailed algebra
E. Experimental E&M (Data and Model Discipline)
- IPhO 2022 E2 — “Cylindrical Diode” (PDF)
- IPhO 2021 E1 — “Non-ideal Capacitors” (PDF)
- IPhO 2016 E1 — “Electrical conductivity” (PDF)
Write-up pattern: experiments that look like circuits
- state the model and what you will plot to make a straight line - label axes with units (including transformed variables) - interpret slope and intercept physically (intercept often captures a systematic offset) - report parameter with uncertainty and one dominant systematic error with direction of effect
Practice loop
Do one symmetry-heavy problem, then one data-heavy experimental section. Then continue via the IPhO Electricity & Magnetism Hub.