Skip to content
Observatory

Unit 04 · Physics 2

Electricity & Magnetism

Fields you cannot see, mapped by what they do, from two point charges to a current conjured out of a moving magnet.

Work through them in order: each lesson assumes the one before it. Every lesson asks you to commit to a prediction, then lets you test it against a simulation of the real equations.

  1. 01

    Charges & Electric Fields

    What one charge does to the space around it, and why a field line is a map of directions, never a track to run along.

    Topics: Coulomb's law · The electric field · Field lines · Superposition

    30 min3 checkpoints
  2. 02

    Flux & Gauss's Law

    Count what crosses a closed surface and the answer forgets everything except the charge sitting inside it.

    Topics: Electric flux · Gauss's law · Closed surfaces · Symmetry

    30 min3 checkpoints
  3. 03

    Electric Potential & Energy

    Trade five vectors for five signed numbers and lose nothing at all in the exchange.

    Topics: Electric potential · Potential energy · Equipotentials · Path independence

    30 min3 checkpoints
  4. 04

    Current, Resistance & Circuits

    Nothing is used up going round the loop except energy, and the battery does not supply a fixed current.

    Topics: Ohm's law · Kirchhoff's rules · Series and parallel · Charging a capacitor

    35 min4 checkpoints
  5. 05

    Magnetic Fields & Forces

    A force that is zero until the charge moves, and that can never change how fast it moves once it does.

    Topics: Magnetic force · Circular orbits · The cyclotron period · Velocity selector

    35 min4 checkpoints
  6. 06

    Induction & Faraday's Law

    A magnet parked inside a coil does nothing at all. Only a changing flux drives a current.

    Topics: Magnetic flux · Faraday's law · Lenz's law · Motional EMF

    30 min4 checkpoints