Electricity & Magnetism

Topics

The mental models this world builds

Each one is a card in the library, taught by one of the topics above.

• Voltage is the push; current is the flow
• The current is the same all round; voltage gets spent
• Series shares the push; parallel shares the flow
• A magnetic field fills the space; field lines map it
• Every current wraps itself in a field
• The right hand reads the field's direction
• Only change induces
• The induced voltage follows how fast the field changes
• The induced current opposes its cause
• A transformer trades volts for amps; power is unchanged
• Line loss is I²R, so the grid runs high volts and low amps
• Only change induces, so the grid alternates

What you will be able to explain

• Keep both ledgers of a circuit: volts round a loop, amps through a junction.
• Say what a battery sets and what the circuit decides.
• Draw the field around a current and read its direction with one hand.
• Say what induces a current, and which way, and why nothing is free.
• Explain why the grid runs on alternating current at very high voltage.

A circuit is energy conservation with wires: the volts a loop spends are the volts it was given. A current makes a field; a changing field makes a current; a transformer is the second fact used on purpose, and the squared term in the loss formula is why.

Labs and games

Pure play. Nothing here is recorded, ever.

• GameThe Amp ExchangeHit exact current and power targets — Ohm and Kirchhoff as a puzzle
• LabCircuit BenchOne battery, up to four bulbs, one wiring choice — predict the current, then let the meters testify